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Aerospace
Volume 9
Issue 4
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Aerospace, Volume 9, Issue 4 (April 2022) – 52 articles

Cover Story (view full-size image): With the increased use of composites in aircraft, many advancements in the field of structural health monitoring (SHM) have been achieved, yet its application is still not often seen in operational conditions, mostly due to a gap between research and application, which constrains the shift toward improved aircraft maintenance strategies such as condition-based maintenance (CBM). This study discusses how data fusion concepts can aid in the maturing of the SHM field for composite aircraft structures and formulates its benefits, opportunities, and challenges. For demonstration purposes, a conceptual design study is included for a representative aircraft wing structure, showing how data fusion concepts can be of benefit in moving towards operational CBM applications in the aircraft industry. View this paper.
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23 pages, 10083 KiB  
Article
Gust Alleviation and Wind Tunnel Test by Using Combined Feedforward Control and Feedback Control
by Yitao Zhou, Zhigang Wu and Chao Yang
Aerospace 2022, 9(4), 225; https://doi.org/10.3390/aerospace9040225 - 18 Apr 2022
Cited by 11 | Viewed by 4711
Abstract
Gust alleviation is of great significance for improving aircraft ride quality and reducing gust load. Using aircraft response (feedback control) and gust disturbance information (feedforward control) to improve the gust alleviation effect is worthy of attention. In this paper, a combined control system [...] Read more.
Gust alleviation is of great significance for improving aircraft ride quality and reducing gust load. Using aircraft response (feedback control) and gust disturbance information (feedforward control) to improve the gust alleviation effect is worthy of attention. In this paper, a combined control system (CCS) composed of feedforward control system (FFCS) and feedback control system (FBCS) is designed and analyzed. At the same time, the gust alleviation effect of the CCS, the single FFCS and the single FBCS are analyzed and compared by means of numerical simulation and wind tunnel test, respectively. Taking a flexible wing as the research object, the gust alleviation effects of three control systems under different forms of gust excitation (1-cos discrete gust, sine gust and Dryden turbulence) are analyzed by numerical simulation. In the wind tunnel test, the sine gust generated by a gust generator was used, and the gust alleviation test was carried out under different wind speeds and gust frequencies. The simulation and experimental results show that the CCS has better gust alleviation performance for various gust excitations. When comparing FFCS and FBCS, the FFCS has better robustness and control effect than the FBCS. When comparing FFCS and CCS, the better the alleviation effect of FFCS, the more difficult it is to achieve significant effect improvement by using CCS, which is obtained by adding FBCS on the FFCS. Full article
(This article belongs to the Section Aeronautics)
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19 pages, 3394 KiB  
Article
Feasibility Study of Electrified Light-Sport Aircraft Powertrains
by Madeline McQueen, Ahmet E. Karataş, Götz Bramesfeld, Eda Demir and Osvaldo Arenas
Aerospace 2022, 9(4), 224; https://doi.org/10.3390/aerospace9040224 - 17 Apr 2022
Cited by 4 | Viewed by 3333
Abstract
A theory-based aerodynamic model developed and applied to electrified powertrain configurations was intended to analyze the feasibility of implementing fully electric and serial hybrid electric propulsion in light-sport aircraft. The range was selected as the primary indicator of feasibility. A MATLAB/Simulink environment was [...] Read more.
A theory-based aerodynamic model developed and applied to electrified powertrain configurations was intended to analyze the feasibility of implementing fully electric and serial hybrid electric propulsion in light-sport aircraft. The range was selected as the primary indicator of feasibility. A MATLAB/Simulink environment was utilized to create the models, involving the combination of proportional-integral-derivative controllers, aerodynamic properties of a reference aircraft, and powertrain limitations taken from off-the-shelf components. Simulations conducted by varying missions, batteries, fuel mass, and energy distribution methods provided results showcasing the feasibility of electrified propulsion with current technology. Results showed that the fully electric aircraft range was only 5% of a traditionally powered aircraft with current battery technology. Hybrid electric aircraft could achieve 44% of the range of a traditionally powered aircraft, but this result was found to be almost wholly related to fuel mass. Hybrid electric powertrains utilizing an energy distribution with their optimal degree of hybridization can achieve ranges up to 3% more than the same powertrain utilizing a different energy distribution. Results suggest that improvements in the power-to-weight ratio of the existing battery technology are required before electrified propulsion becomes a contender in the light-sport aircraft segment. Full article
(This article belongs to the Special Issue Aviation Sustainability)
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9 pages, 3080 KiB  
Technical Note
Automatic Balancing for Satellite Simulators with Mixed Mechanical and Magnetic Actuation
by Andrea Curatolo, Anton Bahu and Dario Modenini
Aerospace 2022, 9(4), 223; https://doi.org/10.3390/aerospace9040223 - 16 Apr 2022
Cited by 3 | Viewed by 2497
Abstract
Dynamic spacecraft simulators are becoming a widespread tool to enable effective on-ground verification of the attitude determination and control subsystem (ADCS). In such facilities, the on-orbit rotational dynamics shall be simulated, thereby requiring minimization of the external torques acting on the satellite mock-up. [...] Read more.
Dynamic spacecraft simulators are becoming a widespread tool to enable effective on-ground verification of the attitude determination and control subsystem (ADCS). In such facilities, the on-orbit rotational dynamics shall be simulated, thereby requiring minimization of the external torques acting on the satellite mock-up. Gravity torque is often the largest among the disturbances, and an automatic procedure for balancing is usually foreseen in such facilities as it is significantly faster and more accurate than manual methods. In this note, we present an automatic balancing technique which combines mechanical and magnetic actuation by the joint use of sliding masses and magnetorquers. A feedback control is employed for in-plane balancing in which the proportional and integral actions are provided by moving the masses, while the derivative action is provided by the magnetorquers. Compared to an earlier implementation by the authors relying on shifting masses only, the novel approach is shown to reduce the in-plane unbalance by an additional 45% on average. Full article
(This article belongs to the Special Issue Verification Approaches for Nano- and Micro-Satellites II)
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17 pages, 10963 KiB  
Article
High-Performance Properties of an Aerospace Epoxy Resin Loaded with Carbon Nanofibers and Glycidyl Polyhedral Oligomeric Silsesquioxane
by Liberata Guadagno, Spiros Pantelakis, Andreas Strohmayer and Marialuigia Raimondo
Aerospace 2022, 9(4), 222; https://doi.org/10.3390/aerospace9040222 - 16 Apr 2022
Cited by 11 | Viewed by 3304
Abstract
This paper proposes a new multifunctional flame retardant carbon nanofiber/glycidyl polyhedral oligomeric silsesquioxane (GPOSS) epoxy formulation specially designed for lightweight composite materials capable of fulfilling the ever-changing demands of the future aerospace industry. The multifunctional resin was designed to satisfy structural and functional [...] Read more.
This paper proposes a new multifunctional flame retardant carbon nanofiber/glycidyl polyhedral oligomeric silsesquioxane (GPOSS) epoxy formulation specially designed for lightweight composite materials capable of fulfilling the ever-changing demands of the future aerospace industry. The multifunctional resin was designed to satisfy structural and functional requirements. In particular, this paper explores the advantages deriving from the combined use of GPOSS and CNFs (short carbon nanofibers) to obtain multifunctional resins. The multifunctional material was prepared by incorporating in the epoxy matrix heat-treated carbon nanofibers (CNFs) at the percentage of 0.5 wt% and GPOSS compound at 5 wt% in order to increase the mechanical performance, electrical conductivity, thermal stability and flame resistance property of the resulting nanocomposite. Dynamic mechanical analysis (DMA) shows that the values of the Storage Modulus (S.M.) of the resin alone and the resin containing solubilized GPOSS nanocages are almost similar in a wide range of temperatures (from 30 °C to 165 °C). The presence of CNFs, in the percentage of 0.5 wt%, determines an enhancement in the S.M. of 700 MPa from −30 °C to 180 °C with respect to the resin matrix and the resin/GPOSS systems. Hence, a value higher than 2700 MPa is detected from 30 °C to 110 °C. Furthermore, the electrical conductivity of the sample containing both GPOSS and CNFs reaches the value of 1.35 × 10−1 S/m, which is a very satisfying value to contrast the electrical insulating property of the epoxy systems. For the first time, TUNA tests have been performed on the formulation where the advantages of GPOSS and CNFs are combined. TUNA investigation highlights an electrically conductive network well distributed in the sample. The ignition time of the multifunctional nanocomposite is higher than that of the sample containing GPOSS alone of about 35%. Full article
(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology III)
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17 pages, 2560 KiB  
Article
Cooperative Smooth Nonsingular Terminal Sliding Mode Guidance with Tracking Differentiator for Active Aircraft Defense
by Quancheng Li, Yonghua Fan, Tian Yan, Xuechao Liang and Jie Yan
Aerospace 2022, 9(4), 221; https://doi.org/10.3390/aerospace9040221 - 15 Apr 2022
Cited by 4 | Viewed by 2144
Abstract
Aimed at the poor performance of guidance algorithms designed based on a linearized model in active defense under large leading angle deviation, both-way and one-way cooperative sliding mode guidance algorithms based on the smooth nonsingular terminal sliding mode for the defense missile are [...] Read more.
Aimed at the poor performance of guidance algorithms designed based on a linearized model in active defense under large leading angle deviation, both-way and one-way cooperative sliding mode guidance algorithms based on the smooth nonsingular terminal sliding mode for the defense missile are proposed. The relative kinematics and linearized models of the target, the active defense missile, and the attacking missile are established. In the design process, two smooth nonsingular terminal sliding mode surfaces are constructed based on zero-effort miss distance and zero-effort velocity, as well as their integral values. A tracking differentiator is introduced for excessive initial command deviation to meet the overload constraints of the active missile and the target. The sensitivity of guidance law to the estimated time-to-go error is reduced, and the target is allowed to perform an independent evasive maneuver. The effectiveness of the proposed guidance strategy is verified by numerical simulation and compared to the existing guidance strategies, the high accuracy, anti-chattering, and strong robustness of the proposed guidance algorithm are verified. Full article
(This article belongs to the Section Aeronautics)
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18 pages, 29304 KiB  
Article
Bionic Design Method of a Non-Uniform Lattice Structure for a Landing Footpad
by Haoyu Deng, Junpeng Zhao and Chunjie Wang
Aerospace 2022, 9(4), 220; https://doi.org/10.3390/aerospace9040220 - 15 Apr 2022
Cited by 3 | Viewed by 2916
Abstract
Due to its excellent performance and high design freedom, the lattice structure has shown excellent capabilities and considerable potential in aerospace and other fields. Inspired by the bamboo structure, a lattice cell configuration namely BCC4IZ is designed and a lattice alternative layout is [...] Read more.
Due to its excellent performance and high design freedom, the lattice structure has shown excellent capabilities and considerable potential in aerospace and other fields. Inspired by the bamboo structure, a lattice cell configuration namely BCC4IZ is designed and a lattice alternative layout is obtained. Then, a design and modeling method for non-uniform lattice structures is proposed. Four designs of the landing footpad with different kinds of lattice cells are developed. A series of dynamic explicit finite element simulations were conducted to evaluate and compare the energy absorption and capacity of resisting impact deformation performance of different designs. The results show that the combination of the bionic design and the lattice structure can effectively improve the performance of the lattice-filled footpad. This study proves the feasibility and potential of application for bionic design in lattice structure. Full article
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19 pages, 5078 KiB  
Article
Assessment of Radiative Heating for Hypersonic Earth Reentry Using Nongray Step Models
by Xinglian Yang, Jingying Wang, Yue Zhou and Ke Sun
Aerospace 2022, 9(4), 219; https://doi.org/10.3390/aerospace9040219 - 15 Apr 2022
Cited by 3 | Viewed by 3253
Abstract
Accurate prediction of the aerothermal environment is of great significance to space exploration and return missions. The canonical Fire II trajectory points are simulated to investigate the radiative transfer in the shock layer for Earth reentry at hypervelocity above 10 km/s using a [...] Read more.
Accurate prediction of the aerothermal environment is of great significance to space exploration and return missions. The canonical Fire II trajectory points are simulated to investigate the radiative transfer in the shock layer for Earth reentry at hypervelocity above 10 km/s using a developed radiation–flowfield uncoupling method. The thermochemical nonequilibrium flow is solved by an in-house PHAROS Navier–Stokes code, while the nongray radiation is integrated by the tangent slab approximation, respectively, combined with the two-, five-, and eight-step models. For the convective heating, the present results agree well with the data of Anderson’s relation. For the radiative heating, the two-step model predicts the closest values with the results of Tauber and Sutton’s relationship, while the five- and eight-step models predict far greater. The three-step models all present the same order of magnitude of radiative heating of 1 MW/m2 and show a consistent tendency with the engineering estimation. The Planck-mean absorption coefficient is calculated to show the radiative transfer significantly occurs in the shock layer. By performing the steady simulation at each flight trajectory point, the present algorithm using a nongray step model with moderate efficiency and reasonable accuracy is promising to solve the real-time problem in engineering for predicting both convective and radiative heating to the atmospheric reentry vehicle in the future. Full article
(This article belongs to the Special Issue Hypersonics: Emerging Research)
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18 pages, 8194 KiB  
Article
Numerical Evaluation of Riblet Drag Reduction on a MALE UAV
by Chris Bliamis, Zinon Vlahostergios, Dimitrios Misirlis and Kyros Yakinthos
Aerospace 2022, 9(4), 218; https://doi.org/10.3390/aerospace9040218 - 14 Apr 2022
Cited by 9 | Viewed by 3916
Abstract
Flow control methods for aerodynamic drag reduction have been a field of interest to aircraft designers, who seek to minimize fuel consumption and increase the aircraft’s aerodynamic performance. Various flow control techniques, applied to aeronautical applications ranging from large airliners to small hand-launched [...] Read more.
Flow control methods for aerodynamic drag reduction have been a field of interest to aircraft designers, who seek to minimize fuel consumption and increase the aircraft’s aerodynamic performance. Various flow control techniques, applied to aeronautical applications ranging from large airliners to small hand-launched unmanned aerial vehicles (UAVs), have been conceptualized, designed and tested in the past. Among others, the concept of riblets, inspired by the shark’s skin morphology, has been proposed and evaluated for airliners. In this work, the implementation of riblets on a medium-altitude long-endurance UAV (MALE) is investigated. The riblets can offer drag reduction due to the decrease in total skin friction, by altering the boundary layer characteristics in the near-wall region. The riblets are implemented on specific locations on the UAV (main wing, fuselage and empennage) and appropriately selected, on which the boundary layer becomes transitional from the laminar to the turbulent flow regime. For this reason, computational fluid dynamics modelling is performed by solving the Reynolds-averaged Navier–Stokes equations, incorporating the k-ω SST eddy viscosity turbulence model. The effect of the riblets in the near-wall region is modelled with the use of an appropriate wall boundary condition for the specific turbulence dissipation rate transport equation. It is shown that a drag reduction benefit, for both the loiter and the cruise flight segments of the UAV mission, can be obtained, and this is clearly presented by the drag polar diagrams of the air vehicle. Finally, the potential benefit to flight performance in terms of endurance and payload weight increase is also evaluated. Full article
(This article belongs to the Section Aeronautics)
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20 pages, 2641 KiB  
Article
Joint State and Parameter Estimation for Hypersonic Glide Vehicles Based on Moving Horizon Estimation via Carleman Linearization
by Yudong Hu, Changsheng Gao and Wuxing Jing
Aerospace 2022, 9(4), 217; https://doi.org/10.3390/aerospace9040217 - 14 Apr 2022
Cited by 3 | Viewed by 2251
Abstract
Aimed at joint state and parameter estimation problems in hypersonic glide vehicle defense, a novel moving horizon estimation algorithm via Carleman linearization is developed in this paper. First, the maneuver characteristic parameters that reflect the target maneuver law are extended into the state [...] Read more.
Aimed at joint state and parameter estimation problems in hypersonic glide vehicle defense, a novel moving horizon estimation algorithm via Carleman linearization is developed in this paper. First, the maneuver characteristic parameters that reflect the target maneuver law are extended into the state vector, and a dynamic tracking model applicable to various hypersonic glide vehicles is constructed. To improve the estimation accuracy, constraints such as path and parameter change amplitude constraints in flight are taken into account, and the estimation problem is transformed into a nonlinear constrained optimal estimation problem. Then, to solve the problem of high time cost for solving a nonlinear constrained optimal estimation problem, in the framework of moving horizon estimation, nonlinear constrained optimization problems are transformed into bilinear constrained optimization problems by linearizing the nonlinear system via Carleman linearization. For ensuring the consistency of the linearized system with the original nonlinear system, the linearized model is continuously updated as the window slides forward. Moreover, a CKF-based arrival cost update algorithm is also provided to improve the estimation accuracy. Simulation results demonstrate that the proposed joint state and parameter estimation algorithm greatly improves the estimation accuracy while reducing the time cost significantly. Full article
(This article belongs to the Special Issue Flight Data)
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24 pages, 2443 KiB  
Article
Preliminary Analysis of Compression System Integrated Heat Management Concepts Using LH2-Based Parametric Gas Turbine Model
by Hamidreza Abedi, Carlos Xisto, Isak Jonsson, Tomas Grönstedt and Andrew Rolt
Aerospace 2022, 9(4), 216; https://doi.org/10.3390/aerospace9040216 - 14 Apr 2022
Cited by 16 | Viewed by 3302
Abstract
The investigation of the various heat management concepts using LH2 requires the development of a modeling environment coupling the cryogenic hydrogen fuel system with turbofan performance. This paper presents a numerical framework to model hydrogen-fueled gas turbine engines with a dedicated heat-management [...] Read more.
The investigation of the various heat management concepts using LH2 requires the development of a modeling environment coupling the cryogenic hydrogen fuel system with turbofan performance. This paper presents a numerical framework to model hydrogen-fueled gas turbine engines with a dedicated heat-management system, complemented by an introductory analysis of the impact of using LH2 to precool and intercool in the compression system. The propulsion installations comprise Brayton cycle-based turbofans and first assessments are made on how to use the hydrogen as a heat sink integrated into the compression system. Conceptual tubular compact heat exchanger designs are explored to either precool or intercool the compression system and preheat the fuel to improve the installed performance of the propulsion cycles. The precooler and the intercooler show up to 0.3% improved specific fuel consumption for heat exchanger effectiveness in the range 0.5–0.6, but higher effectiveness designs incur disproportionately higher pressure losses that cancel-out the benefits. Full article
(This article belongs to the Section Aeronautics)
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21 pages, 1869 KiB  
Article
Probability Analysis of Widespread Fatigue Damage in LY12-CZ Aluminum Alloy Single-Row Seven-Hole Plate
by Kai Liu, Fangli Wang, Wei Pan, Le Yang, Shuwei Bai, Qiang Zhu and Mingbo Tong
Aerospace 2022, 9(4), 215; https://doi.org/10.3390/aerospace9040215 - 14 Apr 2022
Cited by 1 | Viewed by 2125
Abstract
In order to determine the average behavior time of widespread fatigue damage (WFD) in an aircraft multi-site damage (MSD) structure and complete the fatigue analysis of WFD sensitive parts, this paper adopts a probabilistic method to analyze the crack initiation and crack propagation [...] Read more.
In order to determine the average behavior time of widespread fatigue damage (WFD) in an aircraft multi-site damage (MSD) structure and complete the fatigue analysis of WFD sensitive parts, this paper adopts a probabilistic method to analyze the crack initiation and crack propagation of a single row of collinear seven-hole plates. The simulation analysis of the whole process from crack initiation to structural failure is realized. First, through statistical analysis of the test data of the LY12-CZ alloy single-detail plate with hole, the probability distribution of crack initiation life and growth rate is obtained, and this probability distribution is expressed by the randomization of variables. Then, using the related theories of fracture mechanics and fatigue statistics, the whole process of initiation, propagation, and connection of multiple cracks in the MSD structure to the occurrence of WFD was realized through the Monte Carlo method. Finally, a group of single-row seven-hole plate examples are used to verify the accuracy of the calculation results. The results show that the calculated results in this paper are in good agreement with the experimental data, and can accurately predict the life of MSD structures under a certain reliability. Full article
(This article belongs to the Section Aeronautics)
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12 pages, 3779 KiB  
Article
Combustion Characteristics of a Supersonic Combustor with a Large Cavity Length-to-Depth Ratio
by Xiang Li, Qingchun Lei, Xiaocun Zhao, Wei Fan, Shuang Chen, Li Chen, Ye Tian and Quan Zhou
Aerospace 2022, 9(4), 214; https://doi.org/10.3390/aerospace9040214 - 14 Apr 2022
Cited by 7 | Viewed by 2616
Abstract
The combustion characteristics of a hydrogen-fueled supersonic combustor featuring a large cavity length-to-depth ratio (i.e., 11) were examined by performing experimental trials while varying the fuel injector positions and equivalence ratios. During these trials, flame chemiluminescence images were acquired simultaneously from the side [...] Read more.
The combustion characteristics of a hydrogen-fueled supersonic combustor featuring a large cavity length-to-depth ratio (i.e., 11) were examined by performing experimental trials while varying the fuel injector positions and equivalence ratios. During these trials, flame chemiluminescence images were acquired simultaneously from the side and bottom of the combustor under Mach 2.0 inflow conditions. The flame was observed to stabilize inside the cavity under all conditions. Proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) analyses of sequential flame chemiluminescence images demonstrated the important effects of oblique shocks induced by fuel injection and heat release on flame stabilization. Because fluctuations in the locations of the flame and of the intense heat release zone were not observed and no dominant frequency was identified in POD and DMD analyses, the present configuration was evidently able to suppress combustion instability. The present research provides preliminary guidance for exploring the feasibility of using cavity combustors with large length-to-depth ratios in scramjet engines. Full article
(This article belongs to the Special Issue Advanced Flow Diagnostic Tools)
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33 pages, 15774 KiB  
Article
Design and Performance of X-Band SAR Payload for 80 kg Class Flat-Panel-Type Microsatellite Based on Active Phased Array Antenna
by Seok Kim, Chan-Mi Song, Seung-Hun Lee, Sung-Chan Song and Hyun-Ung Oh
Aerospace 2022, 9(4), 213; https://doi.org/10.3390/aerospace9040213 - 13 Apr 2022
Cited by 14 | Viewed by 10465
Abstract
The small synthetic aperture radar (SAR) technology experimental project (S-STEP) mission aims to develop an innovative spaceborne SAR microsatellite as a constellation of 32 microsatellites featuring a high-resolution stripmap mode of 1 m. The S-STEP is a spaceborne SAR microsatellite technology demonstration program [...] Read more.
The small synthetic aperture radar (SAR) technology experimental project (S-STEP) mission aims to develop an innovative spaceborne SAR microsatellite as a constellation of 32 microsatellites featuring a high-resolution stripmap mode of 1 m. The S-STEP is a spaceborne SAR microsatellite technology demonstration program in which innovative approaches have been proposed and investigated for SAR payload system designs for improving the development speed, affordability, size and weight parameters, and quality of SAR satellite systems. In this study, the major design approach includes a bus–payload integrated flat-panel-type SAR payload based on an active phased-array antenna. This study conducted an SAR image performance analysis considering the mission requirements to validate the feasibility of the innovative SAR payload design of the S-STEP. These performance analysis results are presented to demonstrate the effectiveness of the proposed SAR payload design approach under the new space paradigm. Full article
(This article belongs to the Special Issue Advanced Small Satellite Technology)
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15 pages, 3946 KiB  
Article
System Noise Assessment and Uncertainty Analysis of a Conceptual Supersonic Aircraft
by Junichi Akatsuka and Tatsuya Ishii
Aerospace 2022, 9(4), 212; https://doi.org/10.3390/aerospace9040212 - 12 Apr 2022
Cited by 8 | Viewed by 2852
Abstract
This paper describes a system noise assessment of a conceptual supersonic aircraft called the NASA 55t Supersonic Technology Concept Aeroplane (STCA), its prediction uncertainty, and related validation tests. A landing and takeoff noise (LTO) standard for supersonic aircraft is needed to realize future [...] Read more.
This paper describes a system noise assessment of a conceptual supersonic aircraft called the NASA 55t Supersonic Technology Concept Aeroplane (STCA), its prediction uncertainty, and related validation tests. A landing and takeoff noise (LTO) standard for supersonic aircraft is needed to realize future supersonic aircraft, and the noise impact due to the introduction of future supersonic aircraft should be analyzed to develop the standard. System noise assessments and uncertainty analyses using Monte Carlo simulation (MCS) were performed. The predicted noise levels showed good agreement with the prior study for both the benchmark case and statistics of the predictions. The predicted cumulative noise level satisfied the ICAO Chapter 4 noise standard, and its standard deviation was approximately 2 EPNdB. Moreover, sensitivity analysis using the obtained datasets revealed strong correlations with the takeoff noise for jet noise, fan exhaust noise at the flyover measurement point, and airframe trailing edge noise. Further understanding of these extracted factors, which were estimated to have a significant impact on the LTO noise, will be beneficial for the development of LTO noise standards and the design of supersonic aircraft. Full article
(This article belongs to the Special Issue Aircraft Noise)
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22 pages, 6402 KiB  
Article
Simulation of Unsteady Flows of Oil/Gas in the Ventless Bearing Chamber of an Aero-Engine
by Shaobai Li, Caixia Li and Wei Wang
Aerospace 2022, 9(4), 211; https://doi.org/10.3390/aerospace9040211 - 12 Apr 2022
Cited by 3 | Viewed by 2883
Abstract
The unsteady motion behavior of oil/gas two-phase flow in a novel ventless bearing chamber has significant impacts on the lubrication and heat transfer efficiency of bearings due to the various advantages of lower pressure levels and weaker rotating airflow effects. In this paper, [...] Read more.
The unsteady motion behavior of oil/gas two-phase flow in a novel ventless bearing chamber has significant impacts on the lubrication and heat transfer efficiency of bearings due to the various advantages of lower pressure levels and weaker rotating airflow effects. In this paper, the unsteady motion behavior of oil/gas two-phase flow in a ventless aero-engine bearing chamber is investigated by three-dimensional numerical simulation through the volume of fluid (VOF) method, and the numerical method is verified using published experimental data. The flow characteristics of oil/gas two-phase in the secondary flow and three-dimensional flow are investigated. The results show the evolution of vortices and the transition of the driving mode in the unsteady motion of oil/gas two-phase flow, and a criterion for the shift of the driving mode at different rotor speeds is proposed. As the rotation speed increases, the variation trend of the velocity field and pressure field of oil/gas two-phase flow is consistent, and the accumulation region of oil becomes inconspicuous. The results indicate a reference for enhancing the performance of lubrication systems for aero-engines. Full article
(This article belongs to the Section Aeronautics)
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37 pages, 2505 KiB  
Article
On the Feasibility of a Launcher-Deployable High-Altitude Airship: Effects of Design Constraints in an Optimal Sizing Framework
by Carlo E.D. Riboldi, Alberto Rolando and Gregory Regazzoni
Aerospace 2022, 9(4), 210; https://doi.org/10.3390/aerospace9040210 - 11 Apr 2022
Cited by 7 | Viewed by 3290
Abstract
When ground observation or signal relaying in the vicinity of an unfriendly operative scenario are of interest, such as for military actions or disaster relief, high-altitude airships (HAA) offer some technical benefits. Featuring a milder cost and higher deployment flexibility with respect to [...] Read more.
When ground observation or signal relaying in the vicinity of an unfriendly operative scenario are of interest, such as for military actions or disaster relief, high-altitude airships (HAA) offer some technical benefits. Featuring a milder cost and higher deployment flexibility with respect to lower-Earth orbit satellites, these platforms, often baptized as high-altitude pseudo-satellites (HAPS), operate sufficiently far from the ground to provide better imaging coverage and farther-reaching signal relaying than standard low-flying systems, such as aircraft or helicopters. Despite the atmospheric conditions in the higher atmosphere, they offer stable airstreams and highly-predictable solar energy density, thus ideally giving the chance of smooth operation for a prolonged period of time. The design of airships for the task is often conditioned by the need to go through the lower layers of the atmosphere, featuring less predictable and often unstable aerodynamics, during the climb to the target altitude. With the aim of simultaneously largely increasing the ease and quickness of platform deployment, removing most of the design constraints for the HAPS induced by the crossing of the lower atmosphere, and thus allowing for the design of a machine best suited to matching optimal performance at altitude, the deployment of the HAA by means of a missile is an interesting concept. However, since the HAA platform should take the role of a launcher payload, the feasibility of the mission is subject to a careful negotiation of specification, such that the ensuing overall weight of the airship is as low as possible. A preliminary design technique for high-altitude airships is therefore introduced initially, customized to some features typical to missile-assisted deployment, but with the potential for broader applications. The proposed procedure bends itself to the inclusion in an optimal framework, with the aim of seeking a design solution automatically. A validation of the adopted models and assumptions on existing HAPS is proposed first. The design of the airship is then carried out in a parameterized fashion, highlighting the impact of operative and technological constraints on the resulting sizing solutions. This allows for the marking of the boundaries of the space of design solutions for a launcher-deployable airship. Full article
(This article belongs to the Special Issue Mission Analysis and Design of Lighter-than-Air Flying Vehicles)
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25 pages, 7049 KiB  
Article
Adaptive Backstepping Nonsingular Terminal Sliding-Mode Attitude Control of Flexible Airships with Actuator Faults
by Shiqian Liu, James F. Whidborne, Sipeng Song and Weizhi Lyu
Aerospace 2022, 9(4), 209; https://doi.org/10.3390/aerospace9040209 - 11 Apr 2022
Cited by 1 | Viewed by 2565
Abstract
This paper studies the attitude tracking control of a flexible airship subjected to wind disturbances, actuator saturation and control surface faults. Efficient flexible airship models, including elastic deformation, rigid body motions, and their coupling, are established via Lagrange theory. A fast-nonsingular terminal sliding-mode [...] Read more.
This paper studies the attitude tracking control of a flexible airship subjected to wind disturbances, actuator saturation and control surface faults. Efficient flexible airship models, including elastic deformation, rigid body motions, and their coupling, are established via Lagrange theory. A fast-nonsingular terminal sliding-mode (NTSM) combined with a backstepping control is proposed for the problem. The benefits of this approach are NTSM merits of high robustness, fast transient response, and finite time convergence, as well as the backstepping control in terms of globally asymptotic stability. However, the major limitation of the backstepping NTSM is that its design procedure is dependent on the prior knowledge of the bound values of the disturbance and faults. To overcome this limitation, a wind observer is designed to compensate for the effect of the wind disturbances, an anti-windup compensator is designed to compensate for actuator saturation, and an adaptive fault estimator is designed to estimate the faults of the control surfaces. Globally exponential stability of the closed-loop control system is guaranteed by using the Lyapunov stability theory. Finally, simulation results demonstrate effectiveness and advantages of the proposed control for the Skyship-500 flexible airship, even in the presence of unknown wind disturbances, control surface faults, and different stiffness variants. Full article
(This article belongs to the Special Issue Aircraft Modeling for Design, Simulation and Control)
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32 pages, 11419 KiB  
Article
Performance Analysis of Empennage Configurations on a Surveillance and Monitoring Mission of a VTOL-Plane UAV Using a Computational Fluid Dynamics Simulation
by Gesang Nugroho, Galih Zuliardiansyah and Azhar Aulia Rasyiddin
Aerospace 2022, 9(4), 208; https://doi.org/10.3390/aerospace9040208 - 11 Apr 2022
Cited by 5 | Viewed by 10484
Abstract
A Vertical Take-Off and Landing-Plane (VTOL-Plane) is an Unmanned Aerial Vehicle (UAV) that combines multirotor and fixed-wing configurations. It has a good cruise range compared to a VTOL vehicle. Furthermore, it can take-off and land vertically. This technology is ideal for surveillance/monitoring missions [...] Read more.
A Vertical Take-Off and Landing-Plane (VTOL-Plane) is an Unmanned Aerial Vehicle (UAV) that combines multirotor and fixed-wing configurations. It has a good cruise range compared to a VTOL vehicle. Furthermore, it can take-off and land vertically. This technology is ideal for surveillance/monitoring missions and transmitting data in real-time. This study discusses the design of a VTOL-Plane with a preset Design Requirement Objectives (DRO), namely a Maximum Take-Off Weight (MTOW) of 14 kg, a cruise speed of 23 m/s, and a cruising range of 6 h. To maximize the performance, the empennage configurations on the VTOL-Plane varied, and then a Computational Fluid Dynamics (CFD) simulation was carried out. The empennage configurations analyzed were a U-shaped boom, an inverted U-shaped boom, an inverted V-tail boom, and a semi-inverted V-tail boom. The interpreted performance related to the stalling angle, flight efficiency, stability, stall speed, and maneuverability. The relative wind directions toward the longitudinal axis of the UAV, also called the sideslip angle, were varied. The CFD simulation results showed that the empennage configuration of the inverted U-shaped boom is suitable for a surveillance mission. This article also optimized the final empennage design by adding a vertical fin to improve stability. Full article
(This article belongs to the Section Aeronautics)
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21 pages, 7631 KiB  
Article
Intelligent Discrete Sliding Mode Predictive Fault-Tolerant Control Method for Multi-Delay Quad-Rotor UAV System Based on DIECOA
by Pu Yang, Zhiqing Zhang, Huiling Geng, Bin Jiang and Xukai Hu
Aerospace 2022, 9(4), 207; https://doi.org/10.3390/aerospace9040207 - 11 Apr 2022
Cited by 2 | Viewed by 2327
Abstract
This paper introduces a novel intelligent sliding mode predictive fault-tolerant control method based on the Dynamic Information Exchange Coyote Optimization Algorithm (DIECOA), which is applied to a quad-rotor UAV system with multi-delay and sensor fault. First, the system nonlinearity and sensor fault are [...] Read more.
This paper introduces a novel intelligent sliding mode predictive fault-tolerant control method based on the Dynamic Information Exchange Coyote Optimization Algorithm (DIECOA), which is applied to a quad-rotor UAV system with multi-delay and sensor fault. First, the system nonlinearity and sensor fault are dealt with by means of interpolation transformation and system state expansion, and an equivalent system is obtained. Second, the quasi-integral sliding mode surface is used to construct the prediction model so that the initial state of the system is located on the sliding mode surface, and the global robustness is guaranteed. Third, this paper introduces an improved fault and disturbance compensation term, which effectively weakens the adverse effect of time delays and enhances the FTC performance of the system. Fourth, the Dynamic Information Exchange (DIE) strategy is designed to further improve the coyote individual replacement mechanism and speeds up the solution and convergence speed of the method in this paper. Finally, the simulation is carried out on the fault-tolerant simulation platform of the quad-rotor Unmanned Aerial Vehicle (UAV), and the results show the rationality of the method. Full article
(This article belongs to the Section Aeronautics)
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15 pages, 3121 KiB  
Article
Angular-Accelerometer-Based Flexible-State Estimation and Tracking Controller Design for Hypersonic Flight Vehicle
by Daqiao Zhang, Xiaolong Zheng, Yangguang Xie and Xiaoxiang Hu
Aerospace 2022, 9(4), 206; https://doi.org/10.3390/aerospace9040206 - 10 Apr 2022
Cited by 5 | Viewed by 2358
Abstract
The controller design of hypersonic flight vehicles is a challenging task, especially when its flexible states are immeasurable. Unfortunately, the flexible states are difficult to measure directly. In this paper, an angular-accelerometer-based method for the estimation of flexible states is proposed. By adding [...] Read more.
The controller design of hypersonic flight vehicles is a challenging task, especially when its flexible states are immeasurable. Unfortunately, the flexible states are difficult to measure directly. In this paper, an angular-accelerometer-based method for the estimation of flexible states is proposed. By adding a pitch angel angular accelerometer and designing an Extended Kalman Filter-based online estimation method, the flexible states could be obtained in real time. Then, based on the estimated flexible states, a stable inversion-based controller-design method was utilized, and a robust tracking controller was designed for hypersonic flight vehicles. The proposed method provides an effective means of estimating flexible states and conducting the observer-based controller design of hypersonic flight vehicles. Finally, a numeral simulation is given to show the effectiveness of the proposed control method. Full article
(This article belongs to the Special Issue Hypersonics: Emerging Research)
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25 pages, 17902 KiB  
Article
A Polymorphing Wing Capable of Span Extension and Variable Pitch
by Muhammed S. Parancheerivilakkathil, Zawar Haider, Rafic M. Ajaj and Mohammadreza Amoozgar
Aerospace 2022, 9(4), 205; https://doi.org/10.3390/aerospace9040205 - 9 Apr 2022
Cited by 12 | Viewed by 3789
Abstract
This paper presents the development of a novel polymorphing wing capable of Active Span morphing And Passive Pitching (ASAPP) for small UAVs. The span of an ASAPP wing can be actively extended by up to 25% to enhance aerodynamic efficiency, whilst its pitch [...] Read more.
This paper presents the development of a novel polymorphing wing capable of Active Span morphing And Passive Pitching (ASAPP) for small UAVs. The span of an ASAPP wing can be actively extended by up to 25% to enhance aerodynamic efficiency, whilst its pitch near the wingtip can be passively adjusted to alleviate gust loads. To integrate these two morphing mechanisms into one single wing design, each side of the wing is split into two segments (e.g., inboard and outboard segments). The inboard segment is used for span extension whilst the outboard segment is used for passive pitch. The inboard segment consists of a main spar that can translate in the spanwise direction. Flexible skin is used to cover the inboard segment and maintain its aerodynamic shape. The skin transfers the aerodynamic loads to the main spar through a number of ribs that can slide on the main spar through linear plain bearings. A linear actuator located within the fuselage is used for span morphing. The inboard and outboard segments are connected by an overlapping spar surrounded by a torsional spring. The overlapping spar is located ahead of the aerodynamic center of the outboard segment to facilitate passive pitch. The aero-structural design, analysis, and sizing of the ASAPP wing are detailed here. The study shows that the ASAPP wing can be superior to the baseline wing (without morphing) in terms of aerodynamic efficiency, especially when the deformation of the flexible skin is minimal. Moreover, the passive pitching near the wingtip can reduce the root loads significantly, minimizing the weight penalty usually associated with morphing. Full article
(This article belongs to the Special Issue Adaptive/Smart Structures and Multifunctional Materials in Aerospace)
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27 pages, 6323 KiB  
Article
Clean Sky 2 Technology Evaluator—Results of the First Air Transport System Level Assessments
by Marc Christopher Gelhausen, Wolfgang Grimme, Alf Junior, Christos Lois and Peter Berster
Aerospace 2022, 9(4), 204; https://doi.org/10.3390/aerospace9040204 - 9 Apr 2022
Cited by 8 | Viewed by 3587
Abstract
The authors have adjusted the DLR forecast model to evaluate the environmental benefits in terms of CO2 and NOx emissions of Clean Sky 2 technology innovations. The paper briefly describes the model employed: it consists of a passenger/flight volume forecast, a [...] Read more.
The authors have adjusted the DLR forecast model to evaluate the environmental benefits in terms of CO2 and NOx emissions of Clean Sky 2 technology innovations. The paper briefly describes the model employed: it consists of a passenger/flight volume forecast, a fleet model, and emission modelling. The novelty of the forecast approach compared to previous studies is that it is based on airport pairs instead of larger aggregates like countries or regions. Therefore, a separate breakdown on airports is unnecessary in the case of a more detailed analysis is needed, and it enables us to include airport capacity constraints which affect demand and flight volume, as well as the fleet development at constrained and unconstrained airports. We eventually present the forecast results in terms of passenger and flight volume, fleet development, and CO2 and NOx emissions. The results show that emissions can be reduced substantially by the use of Clean Sky 2 technology compared to a reference case which represents the status quo. Full article
(This article belongs to the Special Issue 11th EASN International Conference on Innovation in Aviation & Space to the Satisfaction of the European Citizens)
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25 pages, 14047 KiB  
Article
Design of a DSP-Based Motion-Cueing Algorithm Using the Kinematic Solution for the 6-DoF Motion Platform
by Ming-Yen Wei
Aerospace 2022, 9(4), 203; https://doi.org/10.3390/aerospace9040203 - 9 Apr 2022
Cited by 8 | Viewed by 2986
Abstract
A motion-cueing algorithm is a motion simulation system that makes the pilot feel the flight motion by calculating the attitude of the platform. This paper presents the design a kinematics model and two motion-cueing algorithms for a multi-axis motion platform. Firstly, the relationship [...] Read more.
A motion-cueing algorithm is a motion simulation system that makes the pilot feel the flight motion by calculating the attitude of the platform. This paper presents the design a kinematics model and two motion-cueing algorithms for a multi-axis motion platform. Firstly, the relationship between each axis is derived from the kinematics theory and motion platform transformation. Next, two motion-cueing algorithms are designed providing the pilot with the bodily sensations of the 6-DoF motion platform. By using a hardware-in-the-loop (HIL) approach simulated in a real-time digital simulator, the control operations are performed in a digital signal processor (DSP). All of the motion-cueing algorithms, including the classical washout algorithm and the optimal control algorithm, are realized through a DSP, TMS-320F-28377D. The simulation results verify the theoretical analysis and illustrate the correctness and practicability of the proposed method. Full article
(This article belongs to the Special Issue Flight Simulation and Aircraft Autonomy)
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21 pages, 2665 KiB  
Article
Three-Dimensional Impact Time Control Guidance Considering Field-of-View Constraint and Velocity Variation
by Shuai Ma, Zhongyuan Wang, Xugang Wang and Qi Chen
Aerospace 2022, 9(4), 202; https://doi.org/10.3390/aerospace9040202 - 9 Apr 2022
Cited by 10 | Viewed by 2267
Abstract
The problem of three-dimensional impact time control guidance considering field-of-view constraints and time-varying velocity is investigated in this study. First, considering the effect of gravity and aerodynamic forces on velocity, a simplified numerical estimation algorithm of flight time with a three-dimensional proportional navigation [...] Read more.
The problem of three-dimensional impact time control guidance considering field-of-view constraints and time-varying velocity is investigated in this study. First, considering the effect of gravity and aerodynamic forces on velocity, a simplified numerical estimation algorithm of flight time with a three-dimensional proportional navigation guidance law is derived. Then, based on the structure of the biased proportional navigation guidance law, the effect of the biased term on flight time is analyzed. The biased term is then designed to achieve impact time and field-of-view constraints considering time-varying velocity. Finally, numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed guidance law. Full article
(This article belongs to the Section Aeronautics)
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34 pages, 7206 KiB  
Article
Performance Assessment of an Integrated Environmental Control System of Civil Hypersonic Vehicles
by Nicole Viola, Davide Ferretto, Roberta Fusaro and Roberto Scigliano
Aerospace 2022, 9(4), 201; https://doi.org/10.3390/aerospace9040201 - 7 Apr 2022
Cited by 14 | Viewed by 3766
Abstract
This paper discloses the architecture and related performance of an environment control system designed to be integrated within a complex multi-functional thermal and energy management system that manages the heat loads and generation of electric power in a hypersonic vehicle by benefitting from [...] Read more.
This paper discloses the architecture and related performance of an environment control system designed to be integrated within a complex multi-functional thermal and energy management system that manages the heat loads and generation of electric power in a hypersonic vehicle by benefitting from the presence of cryogenic liquid hydrogen onboard. A bleed-less architecture implementing an open-loop cycle with a boot-strap sub-freezing air cycle machine is suggested. Hydrogen boil-off reveals to be a viable cold source for the heat exchangers of the system as well as for the convective insulation layer designed around the cabin walls. Including a 2 mm boil-off convective layer into the cabin cross-section proves to be far more effective than a more traditional air convective layer of approximately 60 mm. The application to STRATOFLY MR3, a Mach 8 waverider cruiser using liquid hydrogen as propellant, confirmed that presence of cryogenic tanks provides up to a 70% reduction in heat fluxes entering the cabin generated outside of it but inside the vehicle, by the propulsive system and other onboard systems. The effectiveness of the architecture was confirmed for all Mach numbers (from 0.3 to 8) and all flight altitudes (from sea level to 35 km). Full article
(This article belongs to the Special Issue Supersonic and Hypersonic Transportation Systems)
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22 pages, 2175 KiB  
Article
Optimization of Geostationary Orbit Transfers via Combined Chemical–Electric Propulsion
by Shihai Yang, Bo Xu and Xin Li
Aerospace 2022, 9(4), 200; https://doi.org/10.3390/aerospace9040200 - 7 Apr 2022
Viewed by 3462
Abstract
For geostationary orbit transfers, a long duration is required using electric propulsion and a large propellant mass is needed with chemical propulsion. Hybrid transfers can achieve a balance between the fuel consumption and transfer time. In this paper, a trajectory optimization method is [...] Read more.
For geostationary orbit transfers, a long duration is required using electric propulsion and a large propellant mass is needed with chemical propulsion. Hybrid transfers can achieve a balance between the fuel consumption and transfer time. In this paper, a trajectory optimization method is proposed for time-fixed minimum-fuel orbital transfer with combined chemical–electric propulsion. The necessary conditions and transversality conditions related to impulsive burns are derived theoretically with Pontryagin’s maximum principle. The long-duration geostationary orbit transfer is a many-revolution transfer, and is solved with the homotopic approach from the short-duration transfer problem. The variation in fuel consumption with transfer time is nearly linear, and the variation in the magnitude of impulsive burn is exponential. A simple model is presented for the estimation of fuel consumption and magnitude of impulsive burn with given transfer time, specific impulse of propulsion system and low-thrust magnitude. Full article
(This article belongs to the Special Issue Recent Advances in Spacecraft Dynamics and Control)
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23 pages, 6760 KiB  
Article
Orbit-Injection Strategy and Trajectory-Planning Method of the Launch Vehicle under Power Failure Conditions
by Yin Diao, Jialun Pu, Hechuan Xu and Rongjun Mu
Aerospace 2022, 9(4), 199; https://doi.org/10.3390/aerospace9040199 - 7 Apr 2022
Cited by 2 | Viewed by 3302
Abstract
Aiming at the problem of autonomous decision making and trajectory planning (ADMTP) for launch vehicles under power failure conditions, the target degradation order strategy (TDOS) and the trajectory online planning method were studied in this paper. Firstly, the influence of power failure on [...] Read more.
Aiming at the problem of autonomous decision making and trajectory planning (ADMTP) for launch vehicles under power failure conditions, the target degradation order strategy (TDOS) and the trajectory online planning method were studied in this paper. Firstly, the influence of power failure on the orbit-injection process was analyzed. Secondly, the TDOS was proposed according to the mission attribute, failure mode, and multi-payload combination. Then, an online planning method based on the adaptive target update iterative guidance method (ATU-IGM) and radial basis neural network (RBFNN) was proposed, where the ATU-IGM adopted the basic TDOS criterion for generating optimal orbit-injection samples and online guidance instructions, and the RBFNN was used for orbit-injection samples training and online generation of orbital missions. Finally, the comparative simulation analysis was performed under multi-failure conditions. The results showed that the TDOS proposed in this paper could meet the requirements of the mission decision making under different failures, target orbit types, orbit-injection methods, and payload compositions. The online trajectory-planning capability deviation was less than 5%, and the mission decision-making and trajectory-planning time were less than 10 ms. This study provides theoretical support for autonomous decision making and planning of space launch missions. Full article
(This article belongs to the Special Issue Recent Advances in Spacecraft Dynamics and Control)
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19 pages, 4242 KiB  
Article
UAV Imagery for Automatic Multi-Element Recognition and Detection of Road Traffic Elements
by Liang Huang, Mulan Qiu, Anze Xu, Yu Sun and Juanjuan Zhu
Aerospace 2022, 9(4), 198; https://doi.org/10.3390/aerospace9040198 - 6 Apr 2022
Cited by 10 | Viewed by 2761
Abstract
Road traffic elements comprise an important part of roads and represent the main content involved in the construction of a basic traffic geographic information database, which is particularly important for the development of basic traffic geographic information. However, the following problems still exist [...] Read more.
Road traffic elements comprise an important part of roads and represent the main content involved in the construction of a basic traffic geographic information database, which is particularly important for the development of basic traffic geographic information. However, the following problems still exist for the extraction of traffic elements: insufficient data, complex scenarios, small targets, and incomplete element information. Therefore, a set of road traffic multielement remote sensing image datasets obtained by unmanned aerial vehicles (UAVs) is produced, and an improved YOLOv4 network algorithm combined with an attention mechanism is proposed to automatically recognize and detect multiple elements of road traffic in UAV imagery. First, the scale range of different objects in the datasets is counted, and then the size of the candidate box is obtained by the k-means clustering method. Second, mosaic data augmentation technology is used to increase the number of trained road traffic multielement datasets. Then, by integrating the efficient channel attention (ECA) mechanism into the two effective feature layers extracted from the YOLOv4 backbone network and the upsampling results, the network focuses on the feature information and then trains the datasets. At the same time, the complete intersection over union (CIoU) loss function is used to consider the geometric relationship between the object and the test object, to solve the overlapping problem of the juxtaposed dense test element anchor boxes, and to reduce the rate of missed detection. Finally, the mean average precision (mAP) is calculated to evaluate the experimental effect. The experimental results show that the mAP value of the proposed method is 90.45%, which is 15.80% better than the average accuracy of the original YOLOv4 network. The average detection accuracy of zebra crossings, bus stations, and roadside parking spaces is improved by 12.52%, 22.82%, and 12.09%, respectively. The comparison experiments and ablation experiments proved that the proposed method can realize the automatic recognition and detection of multiple elements of road traffic, and provide a new solution for constructing a basic traffic geographic information database. Full article
(This article belongs to the Special Issue Applications of Drones)
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23 pages, 5041 KiB  
Article
Effect of Stagger on Low-Speed Performance of Busemann Biplane Airfoil
by Thai Duong Nguyen, Masashi Kashitani, Masato Taguchi and Kazuhiro Kusunose
Aerospace 2022, 9(4), 197; https://doi.org/10.3390/aerospace9040197 - 6 Apr 2022
Cited by 3 | Viewed by 2922
Abstract
In this study, the low-speed performances of the Busemann biplane were clarified, focusing on the relative contributions of the upper and lower elements to the total aerodynamic characteristics of the biplane. Also, the effects of the staggered biplane, which changes the horizontal distance [...] Read more.
In this study, the low-speed performances of the Busemann biplane were clarified, focusing on the relative contributions of the upper and lower elements to the total aerodynamic characteristics of the biplane. Also, the effects of the staggered biplane, which changes the horizontal distance between two wings in a biplane configuration, were investigated by balance measurements and numerical simulations. The flow velocity was 15 m/s, and the Reynolds number based on the airfoil chord length was 2.1 × 105. In the tests of the integrated biplane wing, the attack angles of the wing elements were varied by a balance system and turntable, which were set in the wind tunnel sidewall. The results show that the lower element generated most of the lift and drag of the Busemann biplane (or the baseline biplane model with no stagger) at high angles of attack. At angles above 20 deg, the contribution of the lower element to total aerodynamic characteristics is almost constant, with 95% of the total lift and 88% of the total drag. The total lift and drag of the baseline model were smaller than the sum of the individual elements that were treated as a single configuration. The increments of lift and drag due to the stagger effects were confirmed, especially at high angles of attack. When the stagger value increases, the high-pressure area near the leading edge of the lower surface of the upper element also increases, which increases the lift and drag of the up-per element. This is the main reason for the increments of total lift and drag of the biplane model. The stagger effects also prevented the leading-edge separation of the lower element in the biplane configuration and increased the lift slopes of the biplane model. Full article
(This article belongs to the Section Aeronautics)
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17 pages, 6632 KiB  
Article
Application of High-Order WENO Scheme in the CFD/FW–H Method to Predict Helicopter Rotor Blade–Vortex Interaction Tonal Noise
by Yan Sun, Yongjie Shi and Guohua Xu
Aerospace 2022, 9(4), 196; https://doi.org/10.3390/aerospace9040196 - 6 Apr 2022
Cited by 8 | Viewed by 2668
Abstract
The accurate prediction of helicopter rotor blade–vortex interaction (BVI) noise is challenging. This paper presents an implementation of the seventh-order improved weighted essentially non-oscillatory (WENO-Z) scheme for predicting rotor BVI noise using a high-resolution numerical method based on the Reynolds-averaged Navier–Stokes and the [...] Read more.
The accurate prediction of helicopter rotor blade–vortex interaction (BVI) noise is challenging. This paper presents an implementation of the seventh-order improved weighted essentially non-oscillatory (WENO-Z) scheme for predicting rotor BVI noise using a high-resolution numerical method based on the Reynolds-averaged Navier–Stokes and the Ffowcs Williams–Hawkings equations. The seventh-order improved WENO-Z scheme is utilized to minimize the inherent numerical dissipation of the reconstruction method in the monotone upstream-centered scheme for conservation laws (MUSCL), thereby improving the rotor wake resolution and the BVI noise-prediction accuracy. The three-layer dummy cell method is used to ensure that the flux at the boundary maintains seventh-order accuracy. The effectiveness of the flow solver and the acoustic solver is validated using the Helishape-7A rotor and the UH-1H rotor, respectively. The flow field and BVI noise characteristics of the OLS rotor obtained from the fifth- and seventh-order WENO-Z schemes are compared with that of the third-order MUSCL for coarse and fine background grids. The wake resolution, noise-prediction accuracy, and computational cost of the three schemes are compared. The results show that the high-order WENO scheme provides higher accuracy for flow field simulation and BVI noise prediction than the MUSCL, but the computational cost of the WENO scheme increases substantially as the grid resolution increases. However, the WENO scheme can predict BVI using a coarser grid than the MUSCL. The computational cost of the WENO scheme is relatively low under the same flow field simulation resolution. Full article
(This article belongs to the Section Aeronautics)
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