Lin-Sen Zhang, Jian-Jun Tao, Guo-Hua Wang, Xiao-Jing Zheng
Lobes and clefts are characteristic structures at the front of sand storms. In this paper, their original formation mechanism and geometric features are studied experimentally and theoretically. A rotatable lock-exchange tank is utilized to avoid the strong local disturbances existing in the conventional horizontal apparatus, and the original lobe size is selected as the dominant spanwise waveleng. . .
Song Wu, Yuehua Yang, Hongyuan Jiang
The ability of particles to stabilize liquid films has broad applications in many fields, such as drug delivery, biofuel catalysis, and crude-oil separation. The mechanism of particles to stabilize emulsions has been widely studied. However, how particles affect the stability of suspension films is still unclear. Here, the dynamics of bacterial particles on free liquid films during evaporation is . . .
Di Peng, Xu Liu, Lingrui Jiao, Ziyan Li, Xin Wen, Chaokai Yuan, Guilai Han, Yunfeng Liu, Yingzheng Liu, Zonglin Jiang
The strong background radiation in high enthalpy hypersonic shock tunnels has posed severe challenges for measurement using luminescent coatings. We proposed a solution for reducing background radiation from time-resolved temperature-sensitive paint (TSP) measure-ment in a hypersonic flow with Ma = 6.5 and T0 = 3525 K. The TSP was applied on an inlet ramp model, and the images were taken by a high. . .
The scope, physical concept, and mathematical model for describing how the rarefaction of the air affects on hypersonic flows have been discussed. A new method, namely the data improved Naive–Stroke (DiNS) model, was proposed for the computation of hypersonic shear flows around vehicles flying at altitude of 30–100 km. Validation of the new continuum method has also been done.
J. Chen, H. Zhou
Recently, as aerodynamics was applied to flying vehicles with very high speed and flying at high altitude, the numerical simulation based on the Navier-Stokes (NS) equations was found that cannot correctly predict certain aero-thermo-dynamic properties in a certain range of velocity and altitude while the Knudsen number indicates that the flow is still in the continuum regime. As first noted by Zh. . .
Wei-Xi Huang, Silas Alben
Fluid–structure interactions (FSI) are encountered by almost all animals and plants that live in fluid environments, e.g. flying insects/birds, swimming fish, blood cells, seeds, leaves, and trees. The interactions of living species with fluids are commonplace in our daily life and have attracted wide attention for a long time. However, they are still puzzling today for their intrinsic compl. . .
Qiang Wei, Yuan-Qing Xu, Xiao-Ying Tang, Fang-Bao Tian
The deterministic lateral displacement (DLD) is an important method used to sort particles and cells of different sizes. In this paper, the flexible cell sorting with the DLD method is studied by using a numerical model based on the immersed boundary-lattice Boltzmann method (IB-LBM). In this model, the fluid motion is solved by the LBM, and the cell membrane-fluid interaction is modeled with the . . .
Zhangli Peng, On Shun Pak, Zhe Feng, Allen P. Liu, Yuan-Nan Young
Mechanosensation is an important process in biological fluid-structure interaction. To understand the biophysics underlying mechanosensation, it is essential to quantify the correlation between membrane deformation, membrane tension, external fluid shear stress, and conformation of mechanosensitive (MS) channels. Smoothed dissipative particle dynamics (SDPD) simulations of vesicle/cell in three ty. . .
Peter D. Yeh, Alexander Alexeev
Using three-dimensional computer simulations, we probe biomimetic free swimming of an internally actuated flexible plate in the regime near the first natural frequency. The plate is driven by an oscillating internal moment approximating the actuation mechanism of a piezoelectric macro fiber composite (MFC) bimorph. We show in our simulations that the addition of a passive attachment increases both. . .
Jaeha Ryu, Sung Goon Park, Boyoung Kim, Hyung Jin Sung
The flapping motion of a flexible propulsor near the ground was simulated using the immersed boundary method. The hydrodynamic benefits of the propulsor near the ground were explored by varying the heaving frequency (St) of the leading edge of the flexible propulsor. Propulsion near the ground had some advantages in generating thrust and propelling faster than propulsion away from the ground. The . . .
Shizhao Wang, Guowei He, Xing Zhang
Flapping-powered propulsion is used by many animals to locomote through air or water. Here we review recent experimental and numerical studies on self-propelled mechanical systems powered by a flapping motion. These studies improve our understanding of the mutual interaction between actively flapping bodies and surrounding fluids. The results obtained in these works provide not only new insights i. . .
Shuoqiao Zhong, Xinbiao Xiao, Zefeng Wen, Xuesong Jin
The flexibility of a train's wheelset can have a large effect on vehicle-track dynamic responses in the medium to high frequency range. To investigate the effects of wheelset bending and axial deformation of the wheel web, a specific coupling of wheel-rail contact with a flexible wheelset is presented and integrated into a conventional vehicle-track dynamic system model. Both conventional and the . . .
San-San Ding, Qiang Li, Ai-Qin Tian, Jian Du, Jia-Li Liu
Compared with the traditional train, the operational speed of the high-speed train has largely improved, and the dynamic environment of the train has changed from one of mechanical domination to one of aerodynamic domination. The aerodynamic problem has become the key technological challenge of high-speed trains and significantly affects the economy, environment, safety, and comfort. In this paper. . .
Dilong Guo, Keming Shang, Ye Zhang, Guowei Yang, Zhenxu Sun
The induced airflow from passing trains, which is recognized as train wind, usually has adverse impacts on people in the surroundings, i.e., the aerodynamic forces generated by a high-speed train's wind may act on the human body and endanger the safety of pedestrians or roadside workers. In this paper, an improved delayed detached eddy simulation (IDDES) method is used to study train wind. The eff. . .
Wen-Jing Wang, Ling-Li Cui, Dao-Yun Chen
Monitoring of potential bearing faults in operation is of critical importance to safe operation of high speed trains. One of the major challenges is how to differentiate relevant signals to operational conditions of bearings from noises emitted from the surrounding environment. In this work, we report a procedure for analyzing acoustic emission signals collected from rolling bearings for diagnosis. . .
Kun Xu, Guo-Qing Xu, Chun-Hua Zheng
The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability, improving the adhesion utilization, and achieving deep energy recovery. There remain technical challenges mainly because of the nonlinear, uncertain, and varying features of wheel-rail contact conditions. This research analyzes the torque transmittin. . .
Jian Han, Guo-Tang Zhao, Xiao-Zhen Sheng, Xue-Song Jin
It is important to study the subgrade characteristics of high-speed railways in consideration of the water-soil coupling dynamic problem, especially when high-speed trains operate in rainy regions. This study develops a nonlinear water-soil interaction dynamic model of slab track coupling with subgrade under high-speed train loading based on vehicle-track coupling dynamics. By using this model, th. . .
Songyan Li, Zhijun Zheng, Jilin Yu, Chunqiang Qian
Dynamic responses of a carriage under excitation with the German high-speed low-interference track spectrum together with the air pressure pulse generated as high-speed trains passing each other are investigated with a multi-body dynamics method. The variations of degrees of freedom (DOFs:horizontal movement, roll angle, and yaw angle), the lateral wheel-rail force, the derailment coefficient, and. . .
Li Guo, Xing Zhang, Guowei He
The flows past a circular cylinder at Reynolds number 3900 are simulated using large-eddy simulation(LES) and the far-field sound is calculated from the LES results. A low dissipation energy-conserving finite volume scheme is used to discretize the incompressible Navier-Stokes equations. The dynamic global coefficient version of the Vreman's subgrid scale(SGS) model is used to compute the sub-grid. . .