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Aerospace
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Fluid Flow Mechanics (3rd Edition)
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Fluid Flow Mechanics (3rd Edition)

A special issue of Aerospace (ISSN 2226-4310).

Deadline for manuscript submissions: closed (15 July 2024) | Viewed by 6436

Special Issue Editor

Dr. Pietro Catalano

E-Mail Website
Guest Editor
Fluid Mechanics Unit, Fluid Dynamic Model Lab, Italian Aerospace Research Centre, Via Maiorise, 81043 Capua, Italy
Interests: turbulence modelling for RANS and LES methods; transition modelling; numerical methods for flow control; drag reduction devices
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Authors are encouraged to submit technical papers in the area of theoretical and computational fluid dynamics relevant to aerospace applications. The focus should be on applied research and advanced modelling and technology developments. Papers providing a comparison between reliable numerical results and certified experimental data are highly encouraged. The main topics that we expect to cover include the following:

  • Low-speed and low-Reynolds-number aerodynamics. Flows that exhibit laminar separation bubbles. Modelling issues connected to bubble length, pressure recovery in the re-attachment region, and turbulence levels inside the bubble.
  • Martian aerodynamics. Modelling issues related to the aerodynamics of vehicles operating in the Martian environment. The very low atmospheric pressure and density, together with low temperatures, means that flight in the Mars atmosphere is characterized by low Reynolds and high Mach numbers simultaneously—a circumstance that seldom occurs on Earth. 
  • Flow control: actuators, applications, and flow physics. Techniques of flow control for avoiding/mitigating separation, reducing aerodynamic drag, and reducing aerodynamic noise.
  • Flow instability and laminar–turbulent transition. Modelling and simulation of flow instabilities. Models that predict boundary-layer transition for RANS equations. 
  • Hybrid RANS/LES models. Topics include turbulence modelling through hybrid RANS/LES methods, zonal and non-zonal approaches, gray-area mitigation issues, turbulence length scale and switching filter, and wall-modelled large-eddy simulation.

Dr. Pietro Catalano
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Aerospace is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • turbulence modelling
  • computational fluid dynamics
  • laminar separation bubbles
  • separation
  • transition

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Related Special Issue

Published Papers (5 papers)

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Research

23 pages, 12084 KiB  
Article
Surface Pressure Measurement of Truncated, Linear Aerospike Nozzles Utilising Secondary Injection for Aerodynamic Thrust Vectoring
by Jan Sieder-Katzmann, Martin Propst, Ralf H. Stark, Dirk Schneider, Stephan General, Martin Tajmar and Christian Bach
Aerospace 2024, 11(7), 507; https://doi.org/10.3390/aerospace11070507 - 24 Jun 2024
Viewed by 1465
Abstract
A cold-gas test campaign has been conducted at the DLR’s P6.2 test bench in Lampoldshausen, with the objective of investigating the linear aerospike nozzle flow in interaction with secondary injection thrust vector control (SITVC). In this campaign, the influence of nozzle truncation, injection [...] Read more.
A cold-gas test campaign has been conducted at the DLR’s P6.2 test bench in Lampoldshausen, with the objective of investigating the linear aerospike nozzle flow in interaction with secondary injection thrust vector control (SITVC). In this campaign, the influence of nozzle truncation, injection position and injection pressure on the nozzle surface and base pressure is analysed using pressure probes and Schlieren flow-visualisation techniques. The effects of injection position and truncation on the nozzle surface pressure development are comparable for all geometric variations, resulting in a locally increased static pressure upstream and a locally decreased static pressure downstream of the injection. The magnitude and dimension of these high- and low-pressure regions are correlated with the injection pressure. However, the influence of injection position and truncation on the base pressure is not entirely predictable by the named parameters, indicating an interdependence between both geometric parameters. Finally, the required pressure ratio of injection to the primary flow to ensure sonic injection has been analysed on TUD’s cold-gas test bench. This allows the respective injection position-dependent threshold to be identified. The analysis reveals that these experiments have been conducted under transsonic injection conditions. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (3rd Edition))
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19 pages, 20066 KiB  
Article
Reduced-Order Modeling of Steady and Unsteady Flows with Deep Neural Networks
by Bryan Barraza and Andreas Gross
Aerospace 2024, 11(7), 506; https://doi.org/10.3390/aerospace11070506 - 24 Jun 2024
Viewed by 895
Abstract
Large-eddy and direct numerical simulations generate vast data sets that are challenging to interpret, even for simple geometries at low Reynolds numbers. This has increased the importance of automatic methods for extracting significant features to understand physical phenomena. Traditional techniques like the proper [...] Read more.
Large-eddy and direct numerical simulations generate vast data sets that are challenging to interpret, even for simple geometries at low Reynolds numbers. This has increased the importance of automatic methods for extracting significant features to understand physical phenomena. Traditional techniques like the proper orthogonal decomposition (POD) have been widely used for this purpose. However, recent advancements in computational power have allowed for the development of data-driven modal reduction approaches. This paper discusses four applications of deep neural networks for aerodynamic applications, including a convolutional neural network autoencoder, to analyze unsteady flow fields around a circular cylinder at Re = 100 and a supersonic boundary layer with Tollmien–Schlichting waves. The autoencoder results are comparable to those obtained with POD and spectral POD. Additionally, it is demonstrated that the autoencoder can compress steady hypersonic boundary-layer profiles into a low-dimensional vector space that is spanned by the pressure gradient and wall-temperature ratio. This paper also proposes a convolutional neural network model to estimate velocity and temperature profiles across different hypersonic flow conditions. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (3rd Edition))
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23 pages, 12377 KiB  
Article
Research on Micro Gap Flow Field Characteristics of Cylindrical Gas Film Seals Based on Experimental and Numerical Simulation
by Zhen Xu, Lianjiang Xu, Junfeng Sun, Meihong Liu, Taohong Liao and Xiangping Hu
Aerospace 2024, 11(1), 40; https://doi.org/10.3390/aerospace11010040 - 29 Dec 2023
Cited by 2 | Viewed by 1111
Abstract
Flexible support cylindrical gas film seals (CGFSs) adapt well to rotor whirling and have a good gas lubrication effect during thermal deformation. However, when a CGFS operates under the “three high” (high interface slip speed, high-pressure differential, and high ambient temperature) operating conditions, [...] Read more.
Flexible support cylindrical gas film seals (CGFSs) adapt well to rotor whirling and have a good gas lubrication effect during thermal deformation. However, when a CGFS operates under the “three high” (high interface slip speed, high-pressure differential, and high ambient temperature) operating conditions, the complex deformation of the support structure is a crucial factor affecting the stability of the CGFS. A thorough and systematic analysis of the micro gap flow field characteristics of flexible support CGFSs is a fundamental problem when we study the deformation of the support structure under multiple physical field conditions. This study uses a cylindrical gas film high-speed rotor test rig to study and compare the sealing characteristics of experiments and numerical simulations and then optimizes and verifies the accuracy and effectiveness of the simulation model. A cross-scale gas film grid model is used to analyze the flow field characteristics and seal ability of different groove models and compare the mechanical characteristics and sealing performance. We also analyze the gas film pressure distribution in micro gaps and explore the impact of dynamic pressure groove microstructure on flow field characteristics. Results show that micro gaps are the primary conditions for generating hydrodynamic effects, and high rotational speed, high-pressure differential, and large eccentricity have a significant effect on improving hydrodynamic effects and enhancing gas film stability. However, an increase in these parameters can cause an increase in leakage rate. A single flow channel makes it easier to improve the hydrodynamic effect, gas film load-bearing ability, and gas film stability while reducing leakage rate. The analyses in this study supplement and improve the theory of the flow field characteristics of cylindrical annular micro gaps and provide a theoretical basis for exploring the relation between the support structural parameters of the CGFS and the mechanical characteristics of the micro gap flow field. This study provides important guidance to the establishment of a quantitative design theory of supporting structures. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (3rd Edition))
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17 pages, 8123 KiB  
Article
Turbulent Boundary Layer Separation Control Using Magnetohydrodynamic Plasma Actuator
by Alexander Kotvitskii, Pavel Kazanskii and Ivan Moralev
Aerospace 2023, 10(11), 907; https://doi.org/10.3390/aerospace10110907 - 25 Oct 2023
Viewed by 1271
Abstract
The pulse electric arc discharge in an external magnetic field is studied as a vortex generator in the subsonic boundary layer. A pulsed Ampere force induces a hairpin vortex near the wall; its structure depends on the relative direction of arc propagation and [...] Read more.
The pulse electric arc discharge in an external magnetic field is studied as a vortex generator in the subsonic boundary layer. A pulsed Ampere force induces a hairpin vortex near the wall; its structure depends on the relative direction of arc propagation and external flow velocity. The data presented in this article were obtained from parametric studies of vortex characteristics and their effects on the boundary layer profile at various actuator momentum coefficients (Cμ=1−30) and vortex sizes relative to the boundary layer thickness (D/δ=0.5−1.2). Also, the control of turbulent boundary layer separation on a bump at a flow velocity up to 50 m/s was attempted. An average shift of the separation line by 15% of the bump height was obtained at a flow velocity of 50 m/s and a total momentum coefficient of 0.6%. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (3rd Edition))
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24 pages, 9154 KiB  
Article
Effect of Bending Deformation on the Lateral Force of Spinning Projectiles with Large Aspect Ratio
by Qi Liu, Juanmian Lei, Yong Yu and Jintao Yin
Aerospace 2023, 10(9), 810; https://doi.org/10.3390/aerospace10090810 - 15 Sep 2023
Cited by 1 | Viewed by 1093
Abstract
The bending deformation can affect the lateral force of spinning projectiles with large aspect ratios, thus interfering with their flight stability. Based on the established spin–deformation coupling motion model, the unsteady Reynolds averaged Navier–Stokes (URANS) equations are solved to simulate the flow over [...] Read more.
The bending deformation can affect the lateral force of spinning projectiles with large aspect ratios, thus interfering with their flight stability. Based on the established spin–deformation coupling motion model, the unsteady Reynolds averaged Navier–Stokes (URANS) equations are solved to simulate the flow over a large−aspect−ratio projectile undergoing spin and spin−deformation coupling motion by using the dual−time stepping method and dynamic mesh technique, obtaining the lateral force. Furtherly, the flow mechanism is analyzed for the changed lateral force induced by the bending deformation. The results indicate that the variation of transient lateral force for the head of a projectile is consistent with that of the deformation−induced additional sideslip angle; affected by the deformation−induced compression wave and expansion wave, the time−averaged lateral force for the middle of a projectile will be increased at small angles of attack, but changed little at large angles of attack; at small angles of attack, the change trend of transient lateral force for the tail of a projectile is similar to that of additional angle of attack caused by the deformation; at large angles of attack, the characteristic of phase lag is presented between the transient lateral force for the tail of a projectile and the additional sideslip angle. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (3rd Edition))
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