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New Advances in Fluid Structure Interaction
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New Advances in Fluid Structure Interaction

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Fluid Science and Technology".

Deadline for manuscript submissions: closed (22 February 2022) | Viewed by 35527

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Prof. Dr. Wenli Chen

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Guest Editor
Key Laboratory of Smart Prevention and Mitigation of Civil Engineering Disasters of Ministry of Industry and Information Technology, Harbin Institute of Technology, Harbin 150090, China
Interests: fluid structure interaction; flow control; bridge wind engineering
Special Issues, Collections and Topics in MDPI journals
Dr. Zifeng Yang

E-Mail Website
Guest Editor
Department of Mechanical and Materials Engineering, Wright State University, Dayton, OH 45435, USA
Interests: hemodynamics; biomechanics; aneurysm; stenosis; In vitro experiment; computational fluid dynamics
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Gang Hu

E-Mail Website
Guest Editor
School of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen 518055, China
Interests: wind engineering; fluid structure interaction; machine learning; deep learning
Dr. Haiquan Jing

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Guest Editor
School of Civil Engineering, Central South University, Changsha 410075, China
Interests: fluid structure interaction; bridge wind engineering
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Junlei Wang

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Guest Editor
School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou 450001, China
Interests: piezoelectric energy harvesting; flow-induced vibrations; energy harvesting from flow phenomena
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fluid–structure interactions (FSI) are a crucial consideration in the design of many engineering systems, e.g., automobiles, aircraft, spacecraft, engines, pipes, offshore platforms and bridges. The old Tacoma Narrows Bridge (1940) is probably one of the most infamous examples of large-scale failure due to FSI. Aircraft wings and turbine blades can break due to FSI oscillations. The dynamics of reed valves used in two-stroke engines and compressors are governed by FSI. The act of "blowing a raspberry" is another such example. In addition, FSI must be dealt with in ocean, coastal, offshore and marine engineering in order to design and construct safe and functional marine structures. 

The Special Issue is focused on the recent progress of fluid–structure interactions in various scenarios of engineering applications and control schemes, which can either mitigate the flow induced motions or harvest energy by enhancing the motion amplitude.

We would like to invite you to contribute a paper to this Special Issue, which aims to collect the most recent and cutting-edge developments on these relevant issues. We welcome papers providing original results on theoretical studies as well as numerical or experimental applications regarding the abovementioned, or closely related, topics.

Prof. Dr. Wenli Chen
Dr. Zifeng Yang
Prof. Dr. Gang Hu
Dr. Haiquan Jing
Prof. Dr. Junlei Wang
Guest Editors

Manuscript Submission Information

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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

  • fluid–structure interaction
  • flow induced vibration and control
  • energy harvesting from flows
  • aerodynamic optimization and its engineering applications
  • vibration suppression via flow control methods
  • bluff-body wake and control
  • AI-based flows and control
  • feedback flow control
  • feedforward flow control

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Published Papers (16 papers)

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Editorial

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2 pages, 160 KiB  
Editorial
New Advances in Fluid–Structure Interaction
by Wenli Chen, Zifeng Yang, Gang Hu, Haiquan Jing and Junlei Wang
Appl. Sci. 2022, 12(11), 5366; https://doi.org/10.3390/app12115366 - 26 May 2022
Viewed by 1768
Abstract
Fluid–structure interactions (FSI) play a crucial role in the design, construction, service and maintenance of many engineering applications, e [...] Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)

Research

Jump to: Editorial

15 pages, 5303 KiB  
Article
An Experimental Investigation of Passive Jet Control Method on Bridge Tower Wake
by Yewei Huang and Wenli Chen
Appl. Sci. 2022, 12(9), 4691; https://doi.org/10.3390/app12094691 - 6 May 2022
Cited by 1 | Viewed by 1486
Abstract
In this study, we employed a four-hole cobra probe to measure the wake characteristics of a rec-tangular bridge tower model in a wind tunnel. The scale of the model was 1:30, and the Reynolds number varied from 1.38 × 105 to 2.27 [...] Read more.
In this study, we employed a four-hole cobra probe to measure the wake characteristics of a rec-tangular bridge tower model in a wind tunnel. The scale of the model was 1:30, and the Reynolds number varied from 1.38 × 105 to 2.27 × 105 by changing the yaw angle. A measurement plane with 9 × 19 measurement points was horizontally set at the middle height behind the model. The wake characteristics of the test model without control, i.e., the baseline case, was first tested in the yaw angle range from 0° to 90°; then, four kinds of passive jet control cases were tested to study their control effects on the bridge tower wake. To evaluate the wake characteristics, three main aspects, i.e., mean velocity, turbulence intensity, and velocity frequency, were investigated. The meas-urement results indicate that the passive jet control method can achieve an effect in suppressing the turbulence of the wake but can slightly modify the mean velocity distribution. The dominant frequency distribution region was eliminated when the yaw angle was small but slightly expanded at a large angle. The differences between cases show a trend that the larger the suction coefficient is, the better the control effects are. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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21 pages, 5879 KiB  
Article
Aerodynamic Shape Optimization of an Arc-Plate-Shaped Bluff Body via Surrogate Modeling for Wind Energy Harvesting
by Tianyi Shi, Gang Hu and Lianghao Zou
Appl. Sci. 2022, 12(8), 3965; https://doi.org/10.3390/app12083965 - 14 Apr 2022
Cited by 7 | Viewed by 2344
Abstract
Galloping-based piezoelectric wind energy harvesters (WEHs) are being used to supply renewable electricity for self-powered devices. This paper investigates the performance of a galloping-based piezoelectric WEH, with different arc-plate-shaped bluff bodies to improve harvesting efficiency. The Latin hypercube sampling method was employed to [...] Read more.
Galloping-based piezoelectric wind energy harvesters (WEHs) are being used to supply renewable electricity for self-powered devices. This paper investigates the performance of a galloping-based piezoelectric WEH, with different arc-plate-shaped bluff bodies to improve harvesting efficiency. The Latin hypercube sampling method was employed to design the experiment. After conducting a series of wind tunnel tests, a Kriging surrogate model was then established, with high accuracy. The results show that the wind energy harvester with an arc angle 0.40π and tail length 1.26D generated the maximum power. The output power of the proposed WEH was doubled by optimizing the aerodynamic shape of the bluff body. The reasons for the improvement are discussed in detail. The force measurement results indicated that a large value of the transverse force coefficient means a large galloping response of the WEH. The aerodynamic optimization of this study can be applied to improve the performance of galloping-based wind energy harvesters. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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12 pages, 1531 KiB  
Article
Research on Equivalent Static Load of High-Rise/Towering Structures Based on Wind-Induced Responses
by Junhui Yang, Junfeng Zhang and Chao Li
Appl. Sci. 2022, 12(8), 3729; https://doi.org/10.3390/app12083729 - 7 Apr 2022
Cited by 2 | Viewed by 1933
Abstract
A method of assessing equivalent static wind loads that can represent all the real ultimate states of a high-rise building and towering structure has still not been fully determined in wind engineering. Based on random vibration theory, the wind-induced response and equivalent static [...] Read more.
A method of assessing equivalent static wind loads that can represent all the real ultimate states of a high-rise building and towering structure has still not been fully determined in wind engineering. Based on random vibration theory, the wind-induced response and equivalent static wind loading of high-rise buildings and towering structures are investigated using the vibration decomposition method. Firstly, the structural wind-induced mean response, background response, resonant response and background and resonant coupled response are studied in the time and frequency domains. Secondly, a new gust load factor (GLF) assessment method suitable for wind-induced displacement, bending moment and shear force response at any height of the structure is proposed, and a typical high-rise building is used as an example for comparison with the previous research results, in order to verify the effectiveness of the method in this paper. The results show the following: for high-rise buildings and towering structures, the percentage of the coupled components in the total pulsation response is less than 2%, and the influence can be ignored; the GLF based on bending moment (MGLF) and the GLF based on shear force (QGLF) increase significantly with height, and the traditional GLF methods underestimate the maximum wind effects. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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20 pages, 40783 KiB  
Article
Aerodynamic Characteristics of a Square Cylinder with Vertical-Axis Wind Turbines at Corners
by Zhuoran Wang, Gang Hu, Dongqin Zhang, Bubryur Kim, Feng Xu and Yiqing Xiao
Appl. Sci. 2022, 12(7), 3515; https://doi.org/10.3390/app12073515 - 30 Mar 2022
Cited by 8 | Viewed by 2468
Abstract
A preliminary study is carried out to investigate the aerodynamic characteristics of a square cylinder with Savonius wind turbines and to explain the reason why this kind of structure can suppress wind-induced vibrations. A series of computational fluid dynamics simulations are performed for [...] Read more.
A preliminary study is carried out to investigate the aerodynamic characteristics of a square cylinder with Savonius wind turbines and to explain the reason why this kind of structure can suppress wind-induced vibrations. A series of computational fluid dynamics simulations are performed for the square cylinders with stationary and rotating wind turbines at the cylinder corners. The turbine orientation and the turbine rotation speed are two key factors that affect aerodynamic characteristics of the cylinder for the stationary and rotating turbine cases, respectively. The numerical simulation results show that the presence of either the stationary or rotating wind turbines has a significant effect on wind forces acting on the square cylinder. For the stationary wind turbine cases, the mean drag and fluctuating lift coefficients decrease by 37.7% and 90.7%, respectively, when the turbine orientation angle is 45°. For the rotating wind turbine cases, the mean drag and fluctuating lift coefficients decrease by 34.2% and 86.0%, respectively, when the rotation speed is 0.2 times of vortex shedding frequency. Wind turbines installed at the corners of the square cylinder not only enhance structural safety but also exploit wind energy simultaneously. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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18 pages, 6705 KiB  
Article
Study on Traveling Wave Wall Control Method for Suppressing Wake of Flow around a Circular Cylinder at Moderate Reynolds Number
by Xin Liu, Weifeng Bai and Feng Xu
Appl. Sci. 2022, 12(7), 3433; https://doi.org/10.3390/app12073433 - 28 Mar 2022
Cited by 6 | Viewed by 2113
Abstract
In the present paper, the computational fluid dynamics (CFD) numerical simulation was utilized to investigate the effectiveness of the transverse traveling wave wall (TWW) method with the expectation of inhibiting the vortex shedding from a fixed circular cylinder. We mainly focused on the [...] Read more.
In the present paper, the computational fluid dynamics (CFD) numerical simulation was utilized to investigate the effectiveness of the transverse traveling wave wall (TWW) method with the expectation of inhibiting the vortex shedding from a fixed circular cylinder. We mainly focused on the variations of four kinds of wave propagation directions, five different maximum wave amplitudes and ten different wave velocities for suppressing vortices shedding and aerodynamic forces. The aerodynamic coefficients and vortex structures under different propagation directions, wave amplitudes, wave numbers and wave velocities were investigated in detail. The results demonstrate that the alternate wake behind the cylinder can be effectively eliminated resorting to the “Downstream” propagating TWW. The mean drag coefficient is positively associated with wave velocity. Drag and lift coefficients remain relatively stable at different wave amplitudes. When the velocity ratio (wave velocity divided by incoming velocity) is 1.5, the lift coefficient fluctuation decreases to the minimum. In contrast, the optimal combination of control parameters under the present Reynolds number is concluded with “Downstream” propagating direction, maximum wave amplitude ratio of 0.02, and velocity ratio of 1.5. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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21 pages, 4533 KiB  
Article
Buffeting Response Prediction of Long-Span Bridges Based on Different Wind Tunnel Test Techniques
by Yi Su, Jin Di, Shaopeng Li, Bin Jian and Jun Liu
Appl. Sci. 2022, 12(6), 3171; https://doi.org/10.3390/app12063171 - 20 Mar 2022
Cited by 5 | Viewed by 2912
Abstract
The traditional method for calculating the buffeting response of long-span bridges follows the strip assumption, and is carried out by identifying aerodynamic parameters through sectional model force or pressure measurement wind tunnel tests. However, there has been no report on predicting the buffeting [...] Read more.
The traditional method for calculating the buffeting response of long-span bridges follows the strip assumption, and is carried out by identifying aerodynamic parameters through sectional model force or pressure measurement wind tunnel tests. However, there has been no report on predicting the buffeting response based on the sectional model vibration test. In recent years, the author has proposed a method, based on the integrated transfer function, for predicting the buffeting response of long-span bridges through theoretical and full-bridge tests. This provided an idea for predicting the buffeting response based on the sectional model vibration test. Unfortunately, the effectiveness and accuracy of this method have not been proven or demonstrated through effective tests. To solve this problem, a long-span suspension bridge was taken as a background. Parameters such as aerodynamic admittance were identified through a sectional model force measurement test and the integrated transfer functions were identified through a sectional model vibration test. A taut strip model test was also conducted. Furthermore, the buffeting response prediction results based on three kinds of wind tunnel test techniques were compared. The results showed that if the strip assumption was established, the results of the three methods aligned well, and that selecting a reasonable model aspect ratio for the test could effectively reduce the influence of the 3D effect; moreover, identifying the integrated transfer function by the sectional model vibration test could effectively predict the long-span bridge buffeting response. Furthermore, when the strip assumption failed, the results of the traditional calculation method using 3D aerodynamic admittance became smaller. A larger result would be obtained by neglecting the influence of aerodynamic admittance. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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21 pages, 17966 KiB  
Article
Fully Convolutional Neural Network Prediction Method for Aerostatic Performance of Bluff Bodies Based on Consistent Shape Description
by Ke Li, Hai Li, Shaopeng Li and Zengshun Chen
Appl. Sci. 2022, 12(6), 3147; https://doi.org/10.3390/app12063147 - 19 Mar 2022
Cited by 9 | Viewed by 2227
Abstract
The shape of a bluff body section is of high importance to its aerostatic performance. Obtaining the aerostatic performance of a specific shape based on wind tunnel tests and CFD simulations takes a lot of time, which affects evaluation efficiency. This paper proposes [...] Read more.
The shape of a bluff body section is of high importance to its aerostatic performance. Obtaining the aerostatic performance of a specific shape based on wind tunnel tests and CFD simulations takes a lot of time, which affects evaluation efficiency. This paper proposes a novel fully convolutional neural network model that enables rapid prediction from shape to aerostatic performance. Its main innovations are: (1) The proposal of a new shape description method in which the shape is described by the combination of the wall distance field and the space coordinate field, which can efficiently express the influencing factors of the shape on the aerostatic performance. (2) A step-by-step strategy in which the pressure field is used as the model output and then the calculation of the aerostatic coefficient is proposed. Compared with the simple direct prediction of the aerostatic coefficient, the logical connection between input and output can be enhanced and the prediction accuracy can be improved. It is found that the model proposed in this paper has good prediction accuracy, and its average relative error is 9.42% compared with the CFD calculation results. Compared with the direct use of the shape as the model input, the accuracy is improved by 13.25%; compared with the direct use of the drag coefficient as the model output, the accuracy is improved by 10%. Compared with traditional CFD calculations and wind tunnel experiments, this method can be used as a fast auxiliary screening method for the optimization of the aerodynamic shapes of bluff body sections. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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17 pages, 5663 KiB  
Article
Effect of Topography Truncation on Experimental Simulation of Flow over Complex Terrain
by Zhen Wang, Yunfeng Zou, Peng Yue, Xuhui He, Lulu Liu and Xiaoyu Luo
Appl. Sci. 2022, 12(5), 2477; https://doi.org/10.3390/app12052477 - 27 Feb 2022
Cited by 4 | Viewed by 1792
Abstract
Wind tunnel tests are a commonly used method for studying wind characteristics of complex terrain; but truncation of the terrain model is usually unavoidable and affects the accuracy of the test results. For this reason, the effects of truncated and original terrain models [...] Read more.
Wind tunnel tests are a commonly used method for studying wind characteristics of complex terrain; but truncation of the terrain model is usually unavoidable and affects the accuracy of the test results. For this reason, the effects of truncated and original terrain models on the simulation of wind characteristics for complex terrain were investigated by considering both nontruncated and truncated models, with the truncated model considering the applicability of two types of transition sections. The results show that the effect of topographic truncation on profiles of mean velocity and turbulence intensity is different for regions and that inclination angle profiles are extremely sensitive to the changing topographic features upwind. In those cases, the spectra of streamwise velocity were overestimated in the low-frequency range but underestimated in the high-frequency range due to topographic truncation. At the same time, the less negative value of the slope of the spectra was found at the inertial subrange. Furthermore, the normalized bandwidth was also influenced by topographic truncation, which was narrowed in windward and leeward regions and broadened in the valley region. We should note that the performance of the transition sections used in this study was quite limited and even resulted in inaccuracies in the simulation. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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35 pages, 13121 KiB  
Article
Moving Surface Boundary-Layer Control on the Wake of Flow around a Square Cylinder
by Te Song, Xin Liu and Feng Xu
Appl. Sci. 2022, 12(3), 1632; https://doi.org/10.3390/app12031632 - 4 Feb 2022
Cited by 5 | Viewed by 2377
Abstract
In this paper, the entire process of the flow around a fixed square cylinder and the moving surface boundary-layer control (MSBC) at a low Reynolds number was numerically simulated. Two small rotating circular cylinders were located in each of the two rear corners [...] Read more.
In this paper, the entire process of the flow around a fixed square cylinder and the moving surface boundary-layer control (MSBC) at a low Reynolds number was numerically simulated. Two small rotating circular cylinders were located in each of the two rear corners of the square cylinder, respectively, to transfer momentum into the near wake behind the square cylinder. The rotations of the two circular cylinders were realized via dynamic mesh technology, when the two-dimensional incompressible Navier–Stokes equations for the flow around the square cylinder were solved. We analyzed the effects of different rotation directions, wind angles θ, and velocity ratios k (the ratio of the tangential velocity of the rotating cylinder to the incoming flow velocity) on the wake of flow around a square cylinder to evaluate the control effectiveness of the MSBC method. In the present work, the aerodynamic forces, the pressure distributions, and the wake patterns of the square cylinder are discussed in detail. The results show that the high suction areas near the surfaces of the rotating cylinders can delay or prevent the separation of the shear layer, reduce the wake width, achieve drag reduction, and eliminate the alternating vortex shedding. For a wind angle of 0°, the inward rotation of the small circular cylinders is the optimal arrangement to manipulate the wake vortex street behind the square cylinder, and k=2 is the optimal velocity ratio between the control effectiveness and external energy consumption. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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23 pages, 4808 KiB  
Article
Dynamic Characteristics of Unsteady Aerodynamic Pressure on an Enclosed Housing for Sound Emission Alleviation Caused by a Passing High-Speed Train
by Haiquan Jing, Xiaoyu Ji, Xuhui He, Shifeng Zhang, Jichao Zhou and Haiyu Zhang
Appl. Sci. 2022, 12(3), 1545; https://doi.org/10.3390/app12031545 - 31 Jan 2022
Cited by 5 | Viewed by 2682
Abstract
Train speed is increasing due to the development of high-speed railway technology. However, high-speed trains generate more noise and discomfort for residents, enclosed housing for sound emission alleviation is needed to further reduce noise. Because these enclosed housings for sound emission alleviation restrain [...] Read more.
Train speed is increasing due to the development of high-speed railway technology. However, high-speed trains generate more noise and discomfort for residents, enclosed housing for sound emission alleviation is needed to further reduce noise. Because these enclosed housings for sound emission alleviation restrain the air flow, strong and complicated aerodynamic pressures are generated inside the housing for sound emission alleviation when a train passes through at a high speed. This train-induced aerodynamic pressure, particularly its dynamic characteristics, is a key parameter in structural design. In the present study, the train-induced unsteady aerodynamic pressure in an enclosed housing for sound emission alleviation is simulated using the dynamic mesh method, and the dynamic characteristics of the aerodynamic pressure are investigated. The simulation results show that when the train is running in the enclosed housing for sound emission alleviation, the unsteady aerodynamic pressure is complicated and aperiodic, and after the train leaves the housing for sound emission alleviation, the aerodynamic pressure reverts to periodic decay curves. Two new terms, the duration of the extreme aerodynamic pressure and the pressure change rate, are proposed to evaluate the dynamic characteristics when the train passes through the barrier. The dominant frequency and decay rate are adopted to express the dynamic characteristics after the train exits. When the train runs in the enclosed housing for sound emission alleviation, the longest durations of the positive and negative extreme aerodynamic pressures are in the middle section, and the maximum change rate of aerodynamic pressure occurs at the entrance area. After the train exits the housing for sound emission alleviation, the pressure amplitude at the central region is always higher than those close to the entrance/exit. The dominant frequency of the aerodynamic pressure is identified and explained using wave propagation theory, the decay rate of the aerodynamic pressure at all sections is close. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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19 pages, 6333 KiB  
Article
Experimental Investigation and Validation on Suppressing the Unsteady Aerodynamic Force and Flow Structure of Single Box Girder by Trailing Edge Jets
by Guanbin Chen and Wenli Chen
Appl. Sci. 2022, 12(3), 967; https://doi.org/10.3390/app12030967 - 18 Jan 2022
Cited by 2 | Viewed by 1492
Abstract
In the present investigation, a wind tunnel experiment was performed to evaluate the effectiveness of the trailing edge jets control scheme to mitigate the unsteady aerodynamic force and flow structure of a single box girder (SBG) model. The flow control scheme uses four [...] Read more.
In the present investigation, a wind tunnel experiment was performed to evaluate the effectiveness of the trailing edge jets control scheme to mitigate the unsteady aerodynamic force and flow structure of a single box girder (SBG) model. The flow control scheme uses four isolated circular holes for forming the jet flow to modify the periodic vortex shedding behind the SBG model and then alleviate the fluctuation of the aerodynamic force acting on the test model. The Reynolds number is calculated as 2.08 × 104 based on the incoming velocity and the height of the test model. A digital pressure measurement system was utilized to obtain and record the surface pressure that was distributed around the SBG model. The surface pressure results show that the fluctuating amplitude of the aerodynamic forces was attenuated in the controlled case at a specific range of the non-dimensional jet momentum coefficient. The Strouhal number of the controlled case also deviates from that of the original SBG model. Except for the pressure measurement experiment, a high-resolution digital particle image velocimetry system was applied to investigate the detailed flow structure behind the SBG model to uncover the unsteady vortex motion process from the SBG model with and without the trailing edge jets flow control. As the jet flow blows into the wake, the alternating vortex shedding mode is switched into a symmetrical shedding mode and the width of the wake flow is narrowed. The proper orthogonal decomposition was used to identify the energy of the different modes and obtain its corresponding flow structures. Moreover, the linear stability analysis of the flow field behind the SBG model shows that the scheme of trailing edge jets can dramatically suppress the area of unsteady flow. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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15 pages, 7650 KiB  
Article
Effect of the Extended Rigid Flapping Trailing Edge Fringe on an S833 Airfoil
by Hongtao Yu and Zifeng Yang
Appl. Sci. 2022, 12(1), 444; https://doi.org/10.3390/app12010444 - 3 Jan 2022
Cited by 4 | Viewed by 2054
Abstract
A 2D numerical simulation was conducted to investigate the effect of an extended rigid trailing edge fringe with a flapping motion on the S833 airfoil and its wake flow field, as an analogy of an owl’s wing. This study aims to characterize the [...] Read more.
A 2D numerical simulation was conducted to investigate the effect of an extended rigid trailing edge fringe with a flapping motion on the S833 airfoil and its wake flow field, as an analogy of an owl’s wing. This study aims to characterize the influence of the extended flapping fringe on the aerodynamic performance and the wake flow characteristics downstream of the airfoil. The length (Le) and flapping frequencies (fe) of the fringe are the key parameters that dominate the impact on the airfoil and the flow field, given that the oscillation angular amplitude is fixed at 5°. The simulation results demonstrated that the airfoil with an extended fringe of 10% of the chord at a flapping frequency of fe = 110 Hz showed a substantial effect on the pressure distribution on the airfoil and the flow characteristics downstream of the airfoil. An irregular vortex street was predicted downstream, thus causing attenuations of the vorticities, and shorter streamwise gaps between each pair of vortices. The extended flapping fringe at a lower frequency than the natural shedding vortex frequency can effectively break the large vortex structure up into smaller scales, thus leading to an accelerated attenuation of vorticities in the wake. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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15 pages, 10692 KiB  
Article
Aerodynamics of a Train and Flat Closed-Box Bridge System with Train Model Mounted on the Upstream Track
by Hui Wang, Huan Li and Xuhui He
Appl. Sci. 2022, 12(1), 276; https://doi.org/10.3390/app12010276 - 28 Dec 2021
Cited by 3 | Viewed by 1695
Abstract
The aerodynamic features of a train and flat closed-box bridge system may be highly sensitive to train-bridge aero interactions. For the generally utilized railway bridge-deck with two tracks (the upstream and downstream ones), the aero interactions above are occupied-track-dependent. The present paper thus [...] Read more.
The aerodynamic features of a train and flat closed-box bridge system may be highly sensitive to train-bridge aero interactions. For the generally utilized railway bridge-deck with two tracks (the upstream and downstream ones), the aero interactions above are occupied-track-dependent. The present paper thus aims to reveal the aero interactions stated above via a series of wind tunnel tests. The results showed that the aero interactions of the present train-bridge system display four typical behaviors, namely, the underbody flow restraining effect, bridge deck shielding effect, flow transition promoting effect, and the flow separation intensifying effect. The above four aero interactions result in obvious reductions in the aerodynamic forces of the train in wind angle of attack α of [−4°, 12°] and in the static stall angle of the bridge-deck, and leads to sensible increases in the absolute values of the bridge aerodynamic forces in α of [−4°, 12°]. Upon comparing the results with the same train and bridge system but with the train model mounted on the downstream track, the quasi-Reynolds number effect was non-detectable when the train model was moved to the upstream track. Thus, no drag crisis and other saltatory aerodynamic behaviors were observed in the present study in α of [0°, 12°]. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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16 pages, 8351 KiB  
Article
Effects of the Configuration of Trailing Edge on the Flutter of an Elongated Bluff Body
by Jie Feng, Buchen Wu and Shujin Laima
Appl. Sci. 2021, 11(22), 10818; https://doi.org/10.3390/app112210818 - 16 Nov 2021
Cited by 2 | Viewed by 1627
Abstract
Wind-tunnel experiments are performed to investigate the effects of trailing-edge reattachment on the flutter behaviors of spring-suspended trailing-edge-changeable section models. Different Trailing edges (TE) were fixed at the back of a body to adjust reattachment of the vortex. A laser-displacement system was used [...] Read more.
Wind-tunnel experiments are performed to investigate the effects of trailing-edge reattachment on the flutter behaviors of spring-suspended trailing-edge-changeable section models. Different Trailing edges (TE) were fixed at the back of a body to adjust reattachment of the vortex. A laser-displacement system was used to acquire the vibration signals. The relationship between flutter characteristics and TEs that affects the wake mode was analyzed. The results show that the motion of the wake vortex has a certain correlation with the flutter stability of the bridge deck. Limit cycle flutter (LCF) occurs to a section model with a 30° TE, whose amplitude gradually increases as the wind speed increases, and the vibration develops into a hard flutter when the wind speed is 12.43 m/s. A section model with 180 TE reaches a hard flutter when the wind speed is 15.31 m/s, without the stage of LCF. As the TE becomes more and more blunt, the critical wind speed, Us, gradually increases, meaning the flutter stability gradually increases. The results reveal that LCF may still occur to the bridge section with a streamlined front edge, and, in some cases, it also may have a range of wind speeds in which LCF occurs. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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17 pages, 13239 KiB  
Article
The Effects of Aerodynamic Interference on the Aerodynamic Characteristics of a Twin-Box Girder
by Buchen Wu, Geng Xue, Jie Feng and Shujin Laima
Appl. Sci. 2021, 11(20), 9517; https://doi.org/10.3390/app11209517 - 13 Oct 2021
Cited by 4 | Viewed by 2018
Abstract
To investigate the aerodynamic characteristics of a twin-box girder in turbulent incoming flow, we carried out wind tunnel tests, including two aerodynamic interferences: leading body-height grid, and leading circular cylinder. In this study, the pressure distribution and the mean and fluctuating aerodynamic forces [...] Read more.
To investigate the aerodynamic characteristics of a twin-box girder in turbulent incoming flow, we carried out wind tunnel tests, including two aerodynamic interferences: leading body-height grid, and leading circular cylinder. In this study, the pressure distribution and the mean and fluctuating aerodynamic forces with the two interferences are compared with bare deck in detail to investigate the relationship between aerodynamic characteristics and the incoming flow characteristics (including Reynolds number and turbulence intensity). The experimental results reveal that, owing to the body-height flow characteristics around the deck interfered with by the body-height grid, the disturbed aerodynamic characteristics of the twin-box girder differ considerably from those of the bare twin-box girder. At the upstream girder, due to the vortex emerging from the body-height grid breaking the separation bubble, pressure plateaus in the upper and lower surface are eliminated. In addition, the turbulence generated by the body-height grid reduces the Reynolds number sensitivity of the twin-box girder. At a relatively high Reynolds number, the fluctuating forces are mainly dominated by turbulence intensity, and the time-averaged forces show almost no change under high turbulence intensity. At a low Reynolds number, the time-averaged forces change significantly with the turbulence intensity. Moreover, at a low Reynolds number, the wake of the leading cylinder effectively forces the boundary layer to transition to turbulence, which reduces the Reynolds number sensitivity of the mean aerodynamic forces and breaks the separation bubbles. Additionally, the fluctuating drag force and the fluctuating lift force are insensitive to the diameter and the spacing ratio. Full article
(This article belongs to the Special Issue New Advances in Fluid Structure Interaction)
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