WAVELET ANALYSIS OF TURBULENT STRUCTURES BEHIND A VEHICLE EXTERNAL MIRROR

摘要

In order to reduce the aerodynamic drag of a vehicle door mirror, the tip shapes of the door mirror are improved by using ditch and concavity in this study. Their aerodynamic drag and the flow structures are quantitatively evaluated. It is found that the aerodynamic drags of the door mirrors can be reduced by the tip shapes of ditch and concavity. The PTV technique was used to measure the instantaneous velocity fields of the mirror wake and the distribution of time-averaged streamlines and Reynolds stresses are examined. Furthermore, the instantaneous turbulent structures are decomposed into the multi-scale structures by the wavelet multi-resolution technique and the distributions of multi-scale Reynolds stresses are analyzed. It is evident that the Reynolds stresses of the small-scale structure can be reduced by improving the tip shape with ditch or concavity.