Journal articles: 'Transient aerodynamic'

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Xiang, Jinwu, Kai Liu, Daochun Li, Chunxiao Cheng, and Enlai Sha. "Unsteady aerodynamic characteristics of a morphing wing." Aircraft Engineering and Aerospace Technology 91, no. 1 (January 7, 2018): 1–9. http://dx.doi.org/10.1108/aeat-04-2017-0101.

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Purpose The purpose of this paper is to investigate the unsteady aerodynamic characteristics in the deflection process of a morphing wing with flexible trailing edge, which is based on time-accurate solutions. The dynamic effect of deflection process on the aerodynamics of morphing wing was studied. Design/methodology/approach The computational fluid dynamic method and dynamic mesh combined with user-defined functions were used to simulate the continuous morphing of the flexible trailing edge. The steady aerodynamic characteristics of the morphing deflection and the conventional deflection were studied first. Then, the unsteady aerodynamic characteristics of the morphing wing were investigated as the trailing edge deflects at different rates. Findings The numerical results show that the transient lift coefficient in the deflection process is higher than that of the static case one in large angle of attack. The larger the deflection frequency is, the higher the transient lift coefficient will become. However, the situations are contrary in a small angle of attack. The periodic morphing of the trailing edge with small amplitude and high frequency can increase the lift coefficient after the stall angle. Practical implications The investigation can afford accurate aerodynamic information for the design of aircraft with the morphing wing technology, which has significant advantages in aerodynamic efficiency and control performance. Originality/value The dynamic effects of the deflection process of the morphing trailing edge on aerodynamics were studied. Furthermore, time-accurate solutions can fully explore the unsteady aerodynamics and pressure distribution of the morphing wing.

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ZHOU, Chao, Yanlai ZHANG, and Jianghao WU. "Aerodynamic periodicity of transient aerodynamic forces of flexible plunging airfoils." Chinese Journal of Aeronautics 34, no. 1 (January 2021): 10–21. http://dx.doi.org/10.1016/j.cja.2020.09.054.

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Huang, Taiming, Zhengqi Gu, Chengjie Feng, and Wei Zeng. "Transient aerodynamics simulations of a road vehicle in the crosswind condition coupled with the vehicle’s motion." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 232, no. 5 (August 11, 2017): 583–98. http://dx.doi.org/10.1177/0954407017704609.

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The influence of transient aerodynamics on a vehicle in a crosswind and the effect on the vehicle’s motion are investigated by employing fully coupled simulations. The fully coupled method makes the simulation data on the fluid dynamics and on the vehicle dynamics exchange in time. LES are used to investigate the movement of the transient turbulence, and wind tunnel experiments are carried out to validate the numerical method. The vehicle is simplified as a three-degree-of-freedom system which moves in only the horizontal direction. The driver’s reaction is considered when the motion of the vehicle is simulated. The results of fully coupled simulations show that the transient aerodynamic loads have a marked influence on the motion of the vehicle. The transitional method of one-way coupled simulations is also employed to obtain data. The simulation results for the two methods are compared with each other. It is found that there is large difference between the results of the two methods. The maximum side force in fully coupled simulations is about 1.22 times the value obtained by the transitional method, and there is a 0.2 m discrepancy between the peak value of the lateral displacement in fully coupled simulations and the peak value in the transitional method. The results show that the transient aerodynamic loads induced by the unsteady motion of the vehicle have a larger effect on the vehicle’s motion than do the aerodynamic loads from the transitional method. Furthermore, the results also reflect the significance of estimating the transient aerodynamic loads in simulations of the vehicle’s motion.

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Shen, Xin, Ping Hu, Jinge Chen, Xiaocheng Zhu, and Zhaohui Du. "The unsteady aerodynamics of floating wind turbine under platform pitch motion." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 232, no. 8 (March 29, 2018): 1019–36. http://dx.doi.org/10.1177/0957650918766606.

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The aerodynamic performance of floating platform wind turbines is much more complex than fixed-base wind turbines because of the flexibility of the floating platform. Due to the extra six degrees-of-freedom of the floating platform, the inflow of the wind turbine rotors is highly influenced by the motions of the floating platform. It is therefore of interest to study the unsteady aerodynamics of the wind turbine rotors involved with the interaction of the floating platform induced motions. In the present work, a lifting surface method with a free wake model is developed for analysis of the unsteady aerodynamics of wind turbines. The aerodynamic performance of the NREL 5 MW floating wind turbine under the prescribed floating platform pitch motion is studied. The unsteady aerodynamic loads, the transient of wind turbine states, and the instability of the wind turbine wakes are discussed in detail.

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Wu, Zhenlong, Can Li, and Yihua Cao. "Numerical Simulation of Rotor–Wing Transient Interaction for a Tiltrotor in the Transition Mode." Mathematics 7, no. 2 (January 22, 2019): 116. http://dx.doi.org/10.3390/math7020116.

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Tiltrotor aerodynamic interaction, especially in the transition mode, is a necessary consideration for tiltrotor aerodynamics, and structural design and optimization. Previous studies have paid much attention to the helicopter mode. However, due to the substantial complexity of the problem, only a small amount of work on the transition mode has been done so far. In this paper, the rotor–wing aerodynamic interaction of a scaled V-22 Osprey tiltrotor, both in the helicopter and transition modes, are studied by computational fluid dynamics (CFD) numerical simulation. The flow field is discretized via the chimera mesh technique and then solved with the Reynolds-averaged Navier–Stokes (RANS) equations. The rotational acceleration of the rotor is considered as a source term added on the right side of the momentum equation of the RANS equations. Both a quasi-steady and a fully transient method are employed to simulate the tilt motion of the rotor in the transition mode. Both qualitative and quantitative results are presented and discussed on the aerodynamic forces, flow physics, and mechanisms. The applicability of the extensively used quasi-steady method for rotor tilt simulation is revealed.

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Hussain, K., H. Rahnejat, and S. Hegazy. "Transient vehicle handling analysis with aerodynamic interactions." Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics 221, no. 1 (March 2007): 21–32. http://dx.doi.org/10.1243/1464419jmbd41.

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Zhang, Zhe, Ying Chao Zhang, and Jie Li. "Vehicles Aerodynamics while Crossing each other on Road Based on Computational Fluid Dynamics." Applied Mechanics and Materials 29-32 (August 2010): 1344–49. http://dx.doi.org/10.4028/www.scientific.net/amm.29-32.1344.

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When vehicles run on road, they will be overtaken, cross by other vehicles or be impacted by crosswind. The other events of overtaking and in crosswind were investigated more deeply. A few of paper report the state of the research on this problem. Until now there are no any wind tunnel and road tests to study on road vehicle aerodynamics while crossing each other. Some numerical simulations were carried out by adopting technology of sliding interface and moving mesh. The method of numerical simulations was narrated in detail. The transient process of vehicles crossing each other was realized. Then the trends of aerodynamic coefficients changing were obtained from the flow field of simulation results. The quantificational changing of vehicles aerodynamic coefficients was obtained when they cross each other. The vehicles are sedan and coach. The simulation results indicated that the all aerodynamic coefficients of two vehicles changed large. The aerodynamic force was important to the vehicles’ handling stability when they cross each other.

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Wu, Da Fang, Shuang Wu, Yue Wu Wang, Zhen Tong Gao, and Jia Ling Yang. "Rapid High-Precision Non-Linear Calibration for Temperature Sensors in Transient Aerodynamic Heating Simulation Systems." Applied Mechanics and Materials 321-324 (June 2013): 618–23. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.618.

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In order to accurately simulate the transient aerodynamic heating conditions experienced by aircraft when flying at high speeds, rapid and highly precise non-linear dynamic control of the heating process in aerodynamic simulation experiments must be conducted using a transient heat flux control system. This process involves carrying out ‘thermoelectric potential - temperature (E-T)’ conversion of sensors. Here a fast and high-precision ‘E-T’ sensor conversion method for the transient aerodynamic heating control systems of high-speed aircraft is proposed. The developed method has the advantages of easy calculation, rapid conversion speed and high calibration precision, and can thus be employed for fast non-linear dynamic control of rapidly-changing temperature fields in the aerodynamic heating process of high-speed aircraft.

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Chen, Zhen, Zhenqqi Gu, and Tao Jiang. "Research on transient aerodynamic characteristics of windshield wipers of vehicles." International Journal of Numerical Methods for Heat & Fluid Flow 29, no. 8 (August 5, 2019): 2870–84. http://dx.doi.org/10.1108/hff-09-2018-0531.

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Purpose The main purpose of this paper is to gain a better understanding of the transient aerodynamic characteristics of moving windshield wipers. In addition, this paper also strives to illustrate and clarify how the wiper motion impacts the airflow structure; the aerodynamic interaction of two wipers is also discussed. Design/methodology/approach A standard vehicle model proposed by the Motor Industry Research Association and a pair of simplified bone wipers are introduced, and a dynamic mesh technique and user-defined functions are used to achieve the wiper motion. Finite volume methods and large eddy simulation (LES) are used to simulate the transient airflow field. The simulation results are validated through the wind tunnel test. Findings The results obtained from the study are presented graphically, and pressure, velocity distributions, airflow structures, aerodynamic drag and lift force are shown. Significant influences of wiper motion on airflow structures are achieved. The maximum value of aerodynamic lift and drag force exists when wipers are rotating and there is a certain change rule. The aerodynamic lift and drag force when wipers are rotating downward is greater than when wipers are rotating upward, and the force when rotating upward is greater than that when steady. The aerodynamic lift and drag forces of the driver-side wiper is greater than those of the passenger-side wiper. Originality/value The LES method in combination with dynamic mesh technique to study the transient aerodynamic characteristics of windshield wipers is relatively new.

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Wu, Da Fang, Yue Wu Wang, Shuang Wu, Jia Ling Yang, and Zhen Tong Gao. "Research on Control of Heat Flux Environment Simulation for High-Speed Aircraft." Advanced Materials Research 705 (June 2013): 528–33. http://dx.doi.org/10.4028/www.scientific.net/amr.705.528.

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The characteristics of the transient heating control process of aerodynamic simulation experiments are complicated, transient, highly nonlinear, and strongly coupled, which make it difficult or impossible to develop a mathematical model. By using the fuzzy control method, many good qualities (such as robustness, high adaptability to changing parameters, and a short transition process time) can be obtained. Based on the fuzzy control method, a transient aerodynamic heating simulation control system for missiles was established. It was demonstrated that quick dynamic control of the aerodynamic simulation heating process according to the transient and continual change in heat flow on the surface of high-speed aircrafts can be completed by using this control system.

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Wang, Jing Yu, Qing Tong Gu, Xing Jun Hu, and Bao Yu Wang. "Numerical Simulation of the Influence of Curvature Radius on Aerodynamic Characteristics of the Moving Vehicle." Applied Mechanics and Materials 532 (February 2014): 328–31. http://dx.doi.org/10.4028/www.scientific.net/amm.532.328.

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Based on moving grid and dynamic boundary conditions, the transient aerodynamic characteristics of the flow field around vehicle were studied when simplified model was driving in the crooked road. The influence of curvature radius on aerodynamic characteristics was studied through the analysis of the drag coefficient, the side drag coefficient and the changes of the flow field. The conclusions provide theoretical reference for the further study of the transient aerodynamic characteristics of turning vehicle.

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Liu, Hao, Xia Sheng Sun, and Xiao Dong Li. "Modal Analysis of Wing Considering Transient Thermal Effects." Applied Mechanics and Materials 444-445 (October 2013): 1400–1406. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.1400.

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The severe aerodynamic heating on the surface of modern hypersonic flight vehicle, that can bring high temperature and large temperature gradients in the structure of the vehicle, will be a challenge for the vehicles design and multidisciplinary optimization. The transient thermal environment consists of high temperature and large temperature gradients will generate two important problems related to vehicle structure, namely: 1) the material property, such as elastic modulus, will be degraded at elevated temperature, and 2) the non-uniform thermal stress cased by large temperature gradients will change the stiffness distribution of wing structure, which can make the modal frequencies and shapes of structure changed remarkably. Firstly, the theory and methodology of structure modal analysis in transient thermal environment is outlined. Subsequently, the transient temperature field of structure considering aerodynamic heating is obtained by employing computational technology of aerodynamic heating/structure heat transfer coupling program. Finally, the modal frequencies and shapes of vehicle structure under transient temperature field is calculated based on finite element method (FEM). Based on the analysis and investigation of the simulation results, the influence of the transient thermal environment on structure modal frequency and shape is determined. Furthermore, the investigation of wing structure modal analysis considering aerodynamic heating is an important basis of aerothermoelastic simulation.

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13

Franke, Daniel, Daniel Möller, Maximilian Jüngst, Heinz-Peter Schiffer, Thomas Giersch, and Bernd Becker. "Experimental Aerodynamic and Aeroelastic Investigation of a Transonic Compressor Rotor with Reduced Blade Count." International Journal of Turbomachinery, Propulsion and Power 6, no. 2 (June 11, 2021): 19. http://dx.doi.org/10.3390/ijtpp6020019.

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This study investigates the aerodynamic and aeroelastic characteristics of a transonic axial compressor, focusing on blade count reduced rotor behavior. The analysis is based on experiments, conducted at the Transonic Compressor Darmstadt test rig at Technical University of Darmstadt and compulsory simulations. In order to obtain measurement data for the detailed aerodynamic and aeroelastic investigation, extensive steady and unsteady instrumentation was applied. Besides transient measurements at the stability limit to determine the operating range and limiting phenomena, performance measurements were performed, presenting promising results with respect to the capabilities of blade count reduced rotors. Close to the stability limit, aerodynamic disturbances like radial vortices were detected for both rotors, varying in size, count, speed and trajectory. Comparing the rotor configurations results in different stability limits along the compressor map as well as varying aeromechanical behavior. Those effects can partially be traced to the variation in blade pitch and associated aerodynamics.

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Liu, Lining, Yumei Sun, Xuefeng Chi, Guangsheng Du, and Meng Wang. "Transient aerodynamic characteristics of vans overtaking in crosswinds." Journal of Wind Engineering and Industrial Aerodynamics 170 (November 2017): 46–55. http://dx.doi.org/10.1016/j.jweia.2017.07.014.

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15

Shkundin, S. Z., S. I. Buyanov, A. V. Vorontsov, and V. A. Rumyantseva. "Modeling Aerodynamic Transient Processes in An Aerometric Plant." Measurement Techniques 57, no. 12 (March 2015): 1396–402. http://dx.doi.org/10.1007/s11018-015-0640-3.

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Wittmeier, Felix, Timo Kuthada, Jakub Filipsky, and Jan Cizek. "New MEMS Pressure Sensors for Transient Aerodynamic Measurements." ATZ worldwide 120, no. 4 (March 15, 2018): 38–41. http://dx.doi.org/10.1007/s38311-018-0010-2.

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Kumar Sinha, Anjani, Eriki Ananda Kumar, and A. Johnrajan. "Flutter Analysis of an Aircraft Wing Using Computational Fluid Dynamics." Applied Mechanics and Materials 754-755 (April 2015): 817–27. http://dx.doi.org/10.4028/www.scientific.net/amm.754-755.817.

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In today’s aviation world, the design of aircraft wing becomes a challenging one for aeronautical engineers, in order to meet the aero elastic phenomenon such as flutter, wing divergence in both aerodynamics and structural aspects. There are so many FEM packages available for both flow and structural analysis such as ANSYS, NASTRAN, ALGOR, NISA, ADINA, COSMOS, etc. The paper presents the application of computational aero-elasticity (CA) methods to analyze the wing in both aerodynamic and structural aspects, using ANSYS-FLOTRAN; 2-D typical aerofoil sections were analyzed and validated with experimental results. Also the vibration behavior of wing section is analyzed under MODAL, HARMONIC, TRANSIENT and SPECTRUM analysis under the aerodynamic lift force and moments. The support reaction forces and moments at the fuselage-wing intersection are developed in this research.

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Fukagawa, Tateru, Shinnosuke Shimokawa, Eiji Itakura, Hiroyuki Nakatani, and Kenichi Kitahama. "Modeling of Transient Aerodynamic Forces based on Crosswind Test." SAE International Journal of Passenger Cars - Mechanical Systems 9, no. 2 (April 5, 2016): 572–82. http://dx.doi.org/10.4271/2016-01-1577.

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Yu, Li, and Xiao Ming. "Study on transient aerodynamic characteristics of parachute opening process." Acta Mechanica Sinica 23, no. 6 (November 7, 2007): 627–33. http://dx.doi.org/10.1007/s10409-007-0112-3.

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Zghal, Bacem, Imen Bel Mabrouk, Lassâad Walha, Kamel Abboudi, and Mohamed Haddar. "Analyses of Dynamic Behavior of Vertical Axis Wind Turbine in Transient Regime." Advances in Acoustics and Vibration 2019 (April 10, 2019): 1–9. http://dx.doi.org/10.1155/2019/7015262.

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In this paper, the dynamic behavior of a one-stage bevel gear used in vertical axis wind turbine in transient regime is investigated. Linear dynamic model is simulated by fourteen degrees of freedom. Gear excitation is induced by external and internal sources which are, respectively, the aerodynamic torque caused by the fluctuation of input wind speed in transient regime and the variation of gear mesh stiffness. In this study, the differential equations governing the system motion are solved using an implicit Newmark algorithm. In fact, there are some design parameters, which influence the performance of vertical axis wind turbine. In order to get the appropriate aerodynamic torque, the effect of each parameter is studied in this work. It was found that the rotational speed of the rotor shaft has a significant effect on the aerodynamic torque performance.

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Reynolds, Kate V., Adrian L. R. Thomas, and Graham K. Taylor. "Wing tucks are a response to atmospheric turbulence in the soaring flight of the steppe eagle Aquila nipalensis." Journal of The Royal Society Interface 11, no. 101 (December 6, 2014): 20140645. http://dx.doi.org/10.1098/rsif.2014.0645.

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Turbulent atmospheric conditions represent a challenge to stable flight in soaring birds, which are often seen to drop their wings in a transient motion that we call a tuck. Here, we investigate the mechanics, occurrence and causation of wing tucking in a captive steppe eagle Aquila nipalensis , using ground-based video and onboard inertial instrumentation. Statistical analysis of 2594 tucks, identified automatically from 45 flights, reveals that wing tucks occur more frequently under conditions of higher atmospheric turbulence. Furthermore, wing tucks are usually preceded by transient increases in airspeed, load factor and pitch rate, consistent with the bird encountering a headwind gust. The tuck itself immediately follows a rapid drop in angle of attack, caused by a downdraft or nose-down pitch motion, which produces a rapid drop in load factor. Positive aerodynamic loading acts to elevate the wings, and the resulting aerodynamic moment must therefore be balanced in soaring by an opposing musculoskeletal moment. Wing tucking presumably occurs when the reduction in the aerodynamic moment caused by a drop in load factor is not met by an equivalent reduction in the applied musculoskeletal moment. We conclude that wing tucks represent a gust response precipitated by a transient drop in aerodynamic loading.

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Chen, Xin, and Lei Yang. "Research on Aerodynamic Noise Reduction with Non-Smooth Surfaces of Exterior Rearview Mirror Cover." Advanced Materials Research 430-432 (January 2012): 1768–72. http://dx.doi.org/10.4028/www.scientific.net/amr.430-432.1768.

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In order to research the car interior aerodynamic noise, the non-smooth surfaces of exterior rearview mirror are studied based on computational fluid dynamics (CFD) and computational aero acoustic (CAA) method. The large eddy simulation model was used to construct transient flow field, and the FW-H acoustic model was used to analyze the aerodynamic noise generated by the exterior rearview mirror. From the comparative analysis on aerodynamic noise spectrum of every monitor point, a conclusion can be drawn that the rearview mirror with non-smooth surfaces can improve the performance of car interior aerodynamic noise.

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Kim, Hak Yoon. "Transient Simulation Method for Autorotation in Forward Flight." Applied Mechanics and Materials 284-287 (January 2013): 1001–6. http://dx.doi.org/10.4028/www.scientific.net/amm.284-287.1001.

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This paper describes the Transient Simulation Method (TSM) which predicts the steady state and performance of autorotation in forward flight. Flapping and rotational equations of motion are integrated from an arbitrary initial rotor speed, and the steady state of autorotation is obtained as a periodic solution through a transient process. The induced velocity field update method and the average thrust, lift, and drag computations during the transition are described in detail. TSM is then applied to the model rotor to validate the feasibility. High speed autorotation is simulated using an aerodynamic data set that is analyzed by the two-dimensional compressible Navier-Stokes Solver. Rotor speed variation for increases in airspeed at low shaft angle is presented and discussed. When TSM is used with sophisticated aerodynamic data analyzed as functions of the blade angle of attack, the Reynolds number, and the Mach number, the autorotation range for the collective pitch, velocity, and shaft angle can be reasonably explored.

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Yan, Jian, Tefang Chen, Shu Cheng, E. Deng, Weichao Yang, Shuaihan Guo, and Zijian Guo. "Influence of Posture Change on Train Running Safety under Crosswind." Applied Sciences 11, no. 13 (June 30, 2021): 6067. http://dx.doi.org/10.3390/app11136067.

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High-speed trains serving in a crosswind region are bearing more significant safety risks. Based on the three-dimensional (3D) Unsteady Reynolds-Averaged Navier–Stokes (URANS) turbulence model, a Computational Fluid Dynamics (CFD) computational work was conducted in the present study to predict the transient aerodynamic load of the train. The transient aerodynamic load was then employed as the input of the dynamic system to perform a dynamic analysis of running safety. Noticeable changes in the aerodynamic coefficients were found when the train entered and left the crosswind region due to the dramatic change in flow patterns. The original posture also provided significant changes to the train’s aerodynamic responses. A slightly larger maximum derailment coefficient was found on the first bogie of the leading car with a preset posture. There were obvious differences in the displacement characteristics of the three cars in the lateral direction and the rolling rotation, and the magnitude of the posture changes decreased from the leading car to the trailing car. The train with the consideration of posture was proven to withstand weaker crosswinds.

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Shi, Wen Ku, Jian Peng Yao, Suo Jun Hou, Fu Xiang Guo, and De Guang Fang. "A Simulation on Aerodynamic Noise of an Air-Conditioning Duck." Advanced Materials Research 466-467 (February 2012): 778–83. http://dx.doi.org/10.4028/www.scientific.net/amr.466-467.778.

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The transient flow field is needed in order to predict the aerodynamic noise of an automotive HVAC duck by conventional methods. However, it is time-consuming when are several improved schemes .To solve the problem, schemes with large sound power can be discarded using Broadband Noise Source (BNS) model at first. Then, the best scheme can be found after the transient flow simulation .In this paper, an automotive HVAC duck is used as an example. Firstly BNS is used to predict which scheme is noisier, secondly the aerodynamic noise is computed using Fluent coupled with Sysnoise. At last they come to the same conclusion. The simulation results indicate BNS model can be used to find which scheme is the best without computing the transient flow field. So it can shorten the cycle of developing new products.

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AIHARA, Yasuhiko, and Hisao KOYAMA. "Transient aerodynamic characteristics of airfoils at high angles of attack." Journal of the Japan Society for Aeronautical and Space Sciences 33, no. 377 (1985): 355–60. http://dx.doi.org/10.2322/jjsass1969.33.355.

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Gupta, Anurag, Joaquin I. Gargoloff, and Bradley D. Duncan. "Response of a Prototype Truck Hood to Transient Aerodynamic Loading." SAE International Journal of Commercial Vehicles 2, no. 1 (April 20, 2009): 75–87. http://dx.doi.org/10.4271/2009-01-1156.

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Noger, C., C. Regardin, and E. Széchényi. "Investigation of the transient aerodynamic phenomena associated with passing manoeuvres." Journal of Fluids and Structures 21, no. 3 (November 2005): 231–41. http://dx.doi.org/10.1016/j.jfluidstructs.2005.05.013.

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Liu, Li-ning, Xing-shen Wang, Guang-sheng Du, Zheng-gang Liu, and Li Lei. "Transient aerodynamic characteristics of vans during the accelerated overtaking process." Journal of Hydrodynamics 30, no. 2 (April 2018): 357–64. http://dx.doi.org/10.1007/s42241-018-0029-2.

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Ivanov, Danil, Dmitry Roldugin, Stepan Tkachev, Yaroslav Mashtakov, Sergey Shestakov, Mikhail Ovchinnikov, Igor Fedorov, Nikolay Yudanov, and Artem Sergeev. "Transient Attitude Motion of TNS-0#2 Nanosatellite during Atmosphere Re-Entry." Applied Sciences 11, no. 15 (July 23, 2021): 6784. http://dx.doi.org/10.3390/app11156784.

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Attitude motion reconstruction of the Technological NanoSatellite TNS-0 #2 during the last month of its mission is presented in the paper. The satellite was designed to test the performance of the data transmission via the Globalstar communication system. This system successfully provided telemetry (even during its atmosphere re-entry) up to an altitude of 156 km. Satellite attitude data for this phase is analyzed in the paper. The nominal satellite attitude represents its passive stabilization along a geomagnetic field induction vector. The satellite was equipped with a permanent magnet and hysteresis dampers. The permanent magnet axis tracked the local geomagnetic field direction with an accuracy of about 15 degrees for almost two years of the mission. Rapid altitude decay during the last month of operation resulted in the transition from the magnetic stabilization to the aerodynamic stabilization of the satellite. The details of the initial tumbling motion after the launch, magnetic stabilization, transition phase prior to the aerodynamic stabilization, and subsequent satellite motion in the aerodynamic stabilization mode are presented.

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Yu, Jia, Hongji Zhu, Li Kong, Haoqing Wang, Jiawen Su, and Qingshan Zhu. "Analysis of Nonlinear Transient Energy Effect on Thermoelectric Energy Storage Structure." Materials 13, no. 16 (August 17, 2020): 3639. http://dx.doi.org/10.3390/ma13163639.

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In complex flight conditions, due to the large amount of unusable heat generated by aerodynamic heating, the thermal protection system of an aircraft needs to withstand a large temperature shock, which brings great challenges to the design of the structure. In order to effectively utilize the irregular aerodynamic heat, and improve structural heat conduction, a composite structure is formed by using phase change energy storage materials on the basis of the thermoelectric structure, which transforms the aerodynamic waste heat into stable electric energy for the internal system. Through the study of the response of nonlinear transient energy, it is found that the thermoelectric and mechanical properties of the new structure can be improved by adding phase change energy storage materials. Under actual flight conditions, the new structure can reduce the maximum temperature by 180 K and the maximum thermal stress by 110 Mpa. The mechanical properties of the structure are effectively improved, the service life of the structure is prolonged, and the waste heat can be converted into stable electrical energy output to improve the thermoelectric output performance. On the premise of ensuring conversion efficiency, the output power of the new structure has been improved by 64.8% through structural optimization under actual flight conditions.

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Alsaeed, A., G. Kirk, and S. Bashmal. "Effects of radial aerodynamic forces on rotor-bearing dynamics of high-speed turbochargers." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 228, no. 14 (February 20, 2014): 2503–19. http://dx.doi.org/10.1177/0954406214520817.

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This study investigates the radial aerodynamic forces that may develop inside the centrifugal compressor and the turbine volutes due to pressure variation of the circulating gas. The forces are numerically predicted for magnitudes, directions, and locations. The radial aerodynamic forces are numerically simulated as static forces in the turbocharger finite element model with floating ring bearings and solved for nonlinear time-transient response. The numerical predictions of the radial aerodynamic forces are computed with correlation to earlier experimental results of the same turbocharger. The outcomes of the investigation demonstrate a significant influence of the radial aerodynamic loads on the turbocharger dynamic stability and the bearing reaction forces. The numerical predictions are also compared with experimental results for validation.

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Yan, Jian, Tefang Chen, E. Deng, Weichao Yang, Shu Cheng, and Biming Zhang. "Aerodynamic Response and Running Posture Analysis When the Train Passes a Crosswind Region on a Bridge." Applied Sciences 11, no. 9 (April 30, 2021): 4126. http://dx.doi.org/10.3390/app11094126.

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Trains running on a bridge face more significant safety risks. Based on the Unsteady Reynolds-Averaged Navier–Stokes turbulence model, a three-dimensional Computational Fluid Dynamics computational model of the train–bridge–wind barrier was proposed in this study to measure the transient aerodynamic load of the train. The transient aerodynamic load was input into the wind–train–bridge coupling dynamic system to perform dynamic analysis of running safety. Significant fluctuations in the aerodynamic coefficients were found when the train entered and exited the wind barrier due to the dramatic change in flow pattern. The maximum value of the derailment coefficient decreased with the height of wind barriers, which hardly affected the wheel load reduction rate. The 2 m high wind barrier had no evident influence on the running posture of a general high-speed train, while the 4 m high wind barrier was proven to have better protection. Over-protection was found with an even higher wind barrier.

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Wu, Da Fang, Shuang Wu, Yue Wu Wang, Zhen Tong Gao, and Jia Ling Yang. "Fast and High Precision Thermoelectric Potential – Temperature Conversion Method for Aerodynamic Heating Control Systems." Advanced Materials Research 694-697 (May 2013): 955–60. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.955.

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A fast and high-precision ‘thermoelectric potential - temperature (E-T)’ sensor conversion method for the transient aerodynamic heating control systems of high-speed aircraft is proposed. The developed method has the advantages of easy calculation, rapid conversion speed and high calibration precision, and can thus be employed for fast non-linear dynamic control of rapidly-changing temperature fields in the aerodynamic heating process of high-speed aircraft.

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Yang, Weichao, E. Deng, Zhihui Zhu, Mingfeng Lei, Chenghua Shi, and Hong He. "Sudden Variation Effect of Aerodynamic Loads and Safety Analysis of Running Trains When Entering Tunnel Under Crosswind." Applied Sciences 10, no. 4 (February 20, 2020): 1445. http://dx.doi.org/10.3390/app10041445.

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Sudden variation of aerodynamic loads is a potential source of safety accidents of high-speed trains (HSTs). As a follow-up investigation on the aerodynamic response of a HST that enters a tunnel under crosswind environment, this paper focuses on the transient response of a HST’s safety indices based on the train–track coupling interaction model. Firstly, a wind–train–track coupling dynamic model is proposed by introducing transient aerodynamic loads into the vehicle–track system. Secondly, the temporal evolution of safety coefficients indicates that the train’s safety risk increases during tunnel entry with crosswind. Results show that the derailment coefficients and wheel load reduction rate during tunnel entry are not only larger than those in open air, but also those inside the tunnel are due to the sudden disappearance of wind excitation at the tunnel entrance. In addition, the characteristic wind curve, which is the wind velocity against the train speed, is presented for application based on the current specification of the safety criteria threshold. The investigation will be useful in assessing the safety risk of a running train subjected to other aerodynamic attacks, such as the coupling effect of an infrastructure scenario and crosswind in a windy area.

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Reich, Gregory W., Franklin E. Eastep, Aaron Altman, and Roberto Albertani. "Transient Poststall Aerodynamic Modeling for Extreme Maneuvers in Micro Air Vehicles." Journal of Aircraft 48, no. 2 (March 2011): 403–11. http://dx.doi.org/10.2514/1.c000278.

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Uystepruyst, David, and Siniša Krajnović. "Numerical simulation of the transient aerodynamic phenomena induced by passing manoeuvres." Journal of Wind Engineering and Industrial Aerodynamics 114 (March 2013): 62–71. http://dx.doi.org/10.1016/j.jweia.2012.12.018.

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Jesson, Michael, Mark Sterling, Chris Letchford, and Matthew Haines. "Aerodynamic forces on generic buildings subject to transient, downburst-type winds." Journal of Wind Engineering and Industrial Aerodynamics 137 (February 2015): 58–68. http://dx.doi.org/10.1016/j.jweia.2014.12.003.

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Li, Li, Guang-sheng Du, Zheng-gang Liu, and Li Lei. "The Transient Aerodynamic Characteristics Around Vans Running Into a Road Tunnel." Journal of Hydrodynamics 22, no. 2 (April 2010): 283–88. http://dx.doi.org/10.1016/s1001-6058(09)60056-1.

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40

Zhu, Lei, Sheng-Nan Shen, Hui Li, Guo-Qing Zhang, and Fu-Hao Cui. "Simulation of aerodynamic noise and vibration noise in hard disk drives." Modern Physics Letters B 32, no. 12n13 (May 10, 2018): 1840050. http://dx.doi.org/10.1142/s021798491840050x.

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Internal flow field characteristics of HDDs are usually influenced by the arm swing during seek operations. This, in turn, can affect aerodynamic noise and airflow-induced noise. In this paper, the dynamic mesh method is used to calculate the flow-induced vibration (FIV) by transient structure analysis and the boundary element method (BEM) is utilized to predict the vibration noise. Two operational states are considered: the arm is fixed and swinging over the disk. Both aerodynamic noise and vibration noise inside drives increase rapidly with increase in disk rotation and arm swing velocities. The largest aerodynamic noise source is always located near the arm and swung with the arm.

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41

Ainsworth, R. W., J. L. Allen, and J. J. M. Batt. "The Development of Fast Response Aerodynamic Probes for Flow Measurements in Turbomachinery." Journal of Turbomachinery 117, no. 4 (October 1, 1995): 625–34. http://dx.doi.org/10.1115/1.2836581.

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The advent of a new generation of transient rotating turbine simulation facilities, where engine values of Reynolds and Mach number are matched simultaneously together with the relevant rotational parameters for dimensional similitude (Dunn et al., 1988; Epstein and Guenette, 1984; Ainsworth et al., 1988), has provided the stimulus for developing improved instrumentation for investigating the aerodynamic flows in these stages. Much useful work has been conducted in the past using hot-wire and laser anemometers. However, hot-wire anemometers are prone to breakage in the high-pressure flows required for correct Reynolds numbers. Furthermore, some laser techniques require a longer run-time than these transient facilities permit, and generally yield velocity information only, giving no data on loss production. Advances in semiconductor aerodynamic probes are beginning to fulfill this perceived need. This paper describes advances made in the design, construction, and testing of two and three-dimensional fast response aerodynamic probes, where semiconductor pressure sensors are mounted directly on the surface of the probes, using techniques that have previously been successfully used on the surface of rotor blades (Ainsworth et al., 1991). These are to be used to measure Mach number and flow direction in compressible unsteady flow regimes. In the first section, a brief review is made of the sensor and associated technology that has been developed to permit a flexible design of fast response aerodynamic probe. Following this, an extensive program of testing large-scale aerodynamic models of candidate geometries for suitable semiconductor scale probes is described, and the results of these discussed. The conclusions of these experiments, conducted for turbine representative mean and unsteady flows, yielded new information for optimizing the design of the small-scale semiconductor probes, in terms of probe geometry, sensor placement, and aerodynamic performance. Details are given of a range of wedge and pyramid semiconductor probes constructed, and the procedures used in calibrating and making measurements with them. Differences in performance are discussed, allowing the experimenter to choose an appropriate probe for the particular measurement required. Finally, the application of prototype semiconductor probes in a transient rotor experiment at HP turbine representative conditions is described, and the data so obtained are compared with CFD solutions of the unsteady viscous flow-field.

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Liu, Xu, Wei Liu, and Yun Fei Zhao. "Review of Research Progresses in Unsteady Aerodynamic Model." Applied Mechanics and Materials 729 (January 2015): 101–7. http://dx.doi.org/10.4028/www.scientific.net/amm.729.101.

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Based on the analysis of the flight stability, the research progress of the unsteady aerodynamic model was comprehensively introduced. Bryan, first of all, the aerodynamic load of traditional dynamic derivative model is put forward, still used today in some engineering issues. However, Bryan state parameters of the model is not complete, not exactly reflect the unsteady aerodynamic force time history effect and nonlinear effect. Etkin models, by retaining the item of high order Taylor expansion, including the influence of nonlinear effect. Improved Etkin model can explain the actual flight of some of the common transient response, including due to stall the mutation and aerodynamic force/torque caused by unsteady flow dynamic bifurcation and chaos of the aerodynamic force/torque value and uncertain phenomenon. Finally, the unsteady flow field of a reduced order model development trends and application prospect were analyzed, and pointing out that the CFD simulation is still accurately predict the plane stability and handling the most important method.

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Sheard, A. G., and R. W. Ainsworth. "The Aerodynamic and Mechanical Performance of a High-Pressure Turbine Stage in a Transient Wind Tunnel." Journal of Turbomachinery 114, no. 1 (January 1, 1992): 132–40. http://dx.doi.org/10.1115/1.2927976.

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A new transient facility for the study of time mean and unsteady aerodynamics and heat transfer in a high-pressure turbine has been commissioned and results are available. A detailed study has been made of aspects of the performance and behavior relevant to turbine mechanical design, and an understanding of the variation of the turbine operating point during the test, crucial to the process of valid data acquisition, has been obtained. In this this paper the outline concept and mode of operation of the turbine test facility are given, and the key aerodynamic and mechanical aspects of the facility’s performance are presented in detail. The variations of the those parameters used to define the turbine operating point during facility operation are examined, and the accuracy with which the turbine’s design point was achieved calculated. Aspects of the mechanical performance presented include the results of a finite element stress analysis of the loads in the turbine under operating conditions, and the performance of the rotor bearing system under these arduous load conditions. Both of these aspects present more information than has been available hitherto. Finally, the future work program and possible plans for further facility improvement are given.

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NICHOLS, JOSEPH W., and SANJIVA K. LELE. "Global modes and transient response of a cold supersonic jet." Journal of Fluid Mechanics 669 (January 31, 2011): 225–41. http://dx.doi.org/10.1017/s0022112010005380.

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Global-mode analysis is applied to a cold, M = 2.5 laminar jet. Global modes of the non-parallel jet capture directly both near-field dynamics and far-field acoustics which, in this case, are coupled by Mach wave radiation. In addition to type (a) modes corresponding to Kelvin–Helmholtz instability, it is found that the jet also supports upstream-propagating type (b) modes which could not be resolved by previous analyses of the parabolized stability equations. The locally neutrally propagating part of a type (a) mode consists of the growth and decay of an aerodynamic wavepacket attached to the jet, coupled with a beam of acoustic radiation at a low angle to the jet downstream axis. Type (b) modes are shown to be related to the subsonic family of modes predicted by Tam & Hu (1989). Finally, significant transient growth is recovered by superposing damped, but non-normal, global modes, leading to a novel interpretation of jet noise production. The mechanism of optimal transient growth is identified with a propagating aerodynamic wavepacket which emits an acoustic wavepacket to the far field at an axial location consistent with the peaks of the locally neutrally propagating parts of type (a) modes.

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Bao, Hai Tao. "Transient Numerical of Piston Wind in Subway Station." Applied Mechanics and Materials 644-650 (September 2014): 467–70. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.467.

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Computational Fluid Dynamics (CFD) is used for the investigation of the piston wind. The Navier-Stokes (N-S) equations and standard turbulence model were applied to set up the model. The train transient aerodynamic characteristic has been research during the crossing process. The simulation results are trustworthy and numerical simulation of piston wind is feasible using dynamic grid in CFD software, which provides the basis for the virtual design of piston wind. It is significant importance for further studying the structure of train, shorten its development and guiding significance for practical application.

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Martins Afonso, Marco, Philippe Meliga, and Eric Serre. "Optimal Transient Growth in an Incompressible Flow past a Backward-Slanted Step." Fluids 4, no. 1 (February 20, 2019): 33. http://dx.doi.org/10.3390/fluids4010033.

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With the aim of providing a first step in the quest for a reduction of the aerodynamic drag on the rear-end of a car, we study the phenomena of separation and reattachment of an incompressible flow by focusing on a specific aerodynamic geometry, namely a backward-slanted step at 25 ∘ of inclination. The ensuing recirculation bubble provides the basis for an analytical and numerical investigation of streamwise-streak generation, lift-up effect, and turbulent-wake and Kelvin–Helmholtz instabilities. A linear stability analysis is performed, and an optimal control problem with a steady volumic forcing is tackled by means of a variational formulation, adjoint methods, penalization schemes, and an orthogonalization algorithm. Dealing with the transient growth of spanwise-periodic perturbations, and inspired by the need of physically-realizable disturbances, we finally provide a procedure attaining a kinetic-energy maximal gain on the order of 10 6 , with respect to the power introduced by the external forcing.

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Dotson, K. W. "Transient Coupling of Launch Vehicle Bending Responses with Aerodynamic Flow State Variations." Journal of Spacecraft and Rockets 38, no. 1 (January 2001): 97–104. http://dx.doi.org/10.2514/2.3660.

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Aihara, Yasuhiko, Hisao Koyama, and Atsushi Murashige. "Transient aerodynamic characteristics of a two-dimensional airfoil during stepwise incidence variation." Journal of Aircraft 22, no. 8 (August 1985): 661–68. http://dx.doi.org/10.2514/3.45183.

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Hu, Xingjun, Limin Fu, Baoqin He, Sheng Li, Yingchao Zhang, and Yunzhu Wu. "Numerical Simulation of Three Dimensional Transient Aerodynamic Characteristics of Two Crossing Vehicles." International Journal for Computational Methods in Engineering Science and Mechanics 8, no. 4 (May 22, 2007): 223–31. http://dx.doi.org/10.1080/15502280701375478.

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Dafang, Wu, Su Fei, Liu Chengxiang, Mao Ronghai, Chen Chinan, Wang Yuewu, and Huang Liang. "Experimental study on mechanical behaviors of Al-alloys under transient aerodynamic heating." International Journal of Mechanics and Materials in Design 6, no. 4 (December 2010): 331–40. http://dx.doi.org/10.1007/s10999-010-9140-4.

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Journal articles on the topic 'Transient aerodynamic'

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