Study On Passive Control Of Corrugated Features For Car Tail Flow-separation

There are many states of flow when fluid flow around object.Flow-separation is one of them.The uncontrolled flow-separation will lower the efficiency of some machines,even cause danger sometimes.For example,the stall of airfoil and the drag force caused by the car tail flow-separation.So,the control of the flow-separation has become an important item of nowadays investigation in engineering.For now,there are many methods have been invented such as vortex generator,blown flap,boundary layer suction.These methods are used in different conditions.And research on control of flow-separation has never been stopped.The effect of corrugated features on car tail flow characteristics has been carried on in this investigation.The Ahmed model was used to generate car tail flow-separation.Firstly,the simulation between corrugated airfoil and flat plate has been carried out came with the conclusion that the separation region of corrugated airfoil was smaller than the separation region of flat plate.Then,installing the corrugated features onto the slant of Ahmed body and transform it roughly.Comparing the flow field and aerodynamic performance between the Ahmed and the corrugated one in different slant angle from 23°to 35°.It can be seen that the Ahmed with corrugated slant has bigger angle when a big flow-separation region appeared.And the reason is that the corrugated features had turned laminar flow into turbulent flow beforehand.The turbulent flow has more energy for reattaching.And the protuberance of corrugated slant made it easier for reattaching.Secondly,an optimization of the corrugated features is carried on the higher ratio of aerodynamic lift to drag.Two parameters of the shape of corrugated features were chosen.And the Optimal Latin Hypercube Design was used as design of experiments.The Radial Basis Functions Model was used as approximation model.The Adaptive Simulated Annealing was used as global optimization.The ratio of aerodynamic lift to drag has improved by 73.93% compared with original model.At last,an experiment in Ji Lin University Wind Tunnel has been carried out to verify the optimization result using Particle Image Velocimetry method.