Flow Control of Fan Wake in the Open-Jet Closed-Circuit Automotive Wind Tunnel

Abstract:

The flow control of the fan wake in the wind tunnel can improve the efficiency of the fan and optimize the quality of the flow field. For the closed-circuit wind tunnel， the global model with the entire flow channel must be used to verify the simulated flow structure and velocity distribution against the measurement data. Results show that for different truncated length of the fan tail， there are two mechanisms of wake control that are closely related to the near-wall large eddy structure. One is the interaction between the large eddies and the small ones induced by the separation flow from the vertical base， and the other one is changing the large eddy structure， which formed from the flow separation and can be strongly influenced by the separation positions due to the surface curving. Both mechanisms can affect the distance between the large vortex structure and the tail cone， and change the velocity distribution of the near-wall shear layer， causing the shear layer to deflect inwardly， resulting in a decrease of the low-velocity area of the wake， increasing the total pressure at the outlet of the main diffusion section， and improving the uniformity of the flow field. After the vortex generators are introduced， the small vortex structure generated by the flow passing through can change the large vortex structure of the wake， then the total pressure and the flow uniformity of the main diffusion section are further improved.

Key words:automotive wind tunnel;fan wake;flow control;vortex generators