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The fluid–structure interaction and aerodynamic shape optimization usually involve the moving or deforming boundaries, thus the dynamic mesh techniques are the key techniques to cope with such deformation. A novel dynamic mesh method was developed based on the Delaunay graph in this paper. According to the Delaunay graph, the mesh points were divid...
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... They concluded that the cycloidal rotor has higher hover efficiency than screw rotor and the elastic torsion of the blade structure can result in smaller aerodynamic force. 2 They also developed remote controlled cyclocopter that flied with good stability. 12, 13 Yang integrated the aero-elastic model into the OVERFLOW and performed numerical simulations with cycloidal propellers. The analysis indicates that both 2D and 3D analysis can produce results that are quite close to the experimental results. ...
... 1,5 Since the mesh elements of the sliding mesh need not to be deformed or re-meshed at each time step, the low quality elements due to mesh deformation or the time to update the mesh are avoided. 13 As shown in Fig. 3, three levels of mesh blocks are deployed in the computation domain. 1 In this approach, a cylindrical hole is cut in the fixed mesh block (i.e. the fixed domain). The rotating mesh block around the cycloidal rotor, named as ''revolving domain", is fitted into that hole. ...
In recent years, a lot of research work has been carried out on the cycloidal rotors. However, it lacks thorough understanding about the effects of the blade platform shape on the hover efficiency of the cycloidal rotor, and the knowledge of how to design the platform shape of the blades. This paper presents a numerical simulation model based on Unsteady Reynolds-Averaged Navier–Stokes equations (URANSs), which is further validated by the experimental results. The effects of blade aspect ratio and taper ratio are analyzed, which shows that the cycloidal rotors with the same chord length have quite similar performance even though the blade aspect ratio varies from a very small value to a large one. By comparing the cycloidal rotors with different taper ratios, it is found that the rotors with large blade taper ratio outperform those with small taper ratio. This is due to the fact that the blade with larger taper ratio has longer chord and hence better efficiency. The analysis results show that the unsteady aerodynamic effects due to blade pitching motion play a more important role in the efficiency than the blade platform shape. Therefore we should pay more attention to the blade airfoil and pitching motion than the blade platform shape. The main contributions of this paper include: the analysis of the effects of aspect ratio and taper ratio on the hover efficiency of cycloidal rotor based on both the experimental and numerical simulation results; the finding of the main influencing factors on the hover efficiency; the qualitative guidance on how to design the blade platform shape for cycloidal rotors. Keywords: Blade pitching motion, Cyclocopter, Cyclogyro, Cycloidal rotor, Dynamic stall
... They concluded that the cycloidal rotor has higher hover efficiency than screw rotor and the elastic torsion of the blade structure can result in smaller aerodynamic force 2 . They also developed remote controlled cyclocopter that flied with good stability 12,13 . Yang integrated the aero-elastic model into the OVERFLOW and performed numerical simulations with cycloidal propellers. ...
Piston type valve cores are widely adopted in check valves, globe valves, pressure reducing valves and so forth. With the irregular inlet flow channel, the bottom of piston type valve core exits unbalanced torques usually. The unbalanced torque causes the valve core to squeeze sealing elements and increases the energy consumption. To analyze the unbalanced torque on the bottom of the piston type valve core, a transient numerical model of the piston type valve core is established and the simulation results are compared with the theoretical formula for the purpose of validation. The dynamic flow characteristics are studied to investigate pressure characteristics on the bottom of the piston type valve core with the dynamic motion of the valve core. Meanwhile, pressure characteristics under different valve core displacements are obtained, and the sensitive range of the unbalanced torque is found. This work can be helpful for the further structural optimization on the valves with piston type valve cores.
