Aerodynamic Characteristics and Change Rules ofVehicle Piston Wind in Evacuated Tube
Piston wind is the main aerodynamic characteristics of the flow field in the evacuated tube,and thus grasping the basic characteristics and variation rules of the piston wind is the basis of a reasonable and effective control of the flow field of the tube. In this paper, the influences of piston air generation mechanism,aerodynamic characteristics and degrees of vacuum,blockage ratios, driving speeds and other conditions on the piston wind were analyzed and discussed by using the methods of computational fluid dynamics and dynamic meshing. This study finds that air in the pipeline is compressed and inflated during the running of the vehicle, producing compression and expansion waves and affecting the vehicle's driving resistance；Through a comprehensive analysis on a series of combined calculations for different degrees of vacuum,blockage ratios and driving speeds,it is found that the vehicle's driving resistance increases with the growth of the blocking ratio,pressure, and speed. Further,when the speed increases to a threshold, the increase of the vehicle’s driving resistance begins to slow down.
Keywords: evacuated tube transportation, piston wind, computational fluid dynamics, mechanism
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