Side-view mirrors impact the aerodynamic performance of vehicles due to the creation of extra drag force, noise, and vibration. A CFD analysis is presented for studying the airflow around a side-view mirror with different types of passive vortex generators (VGs) mounted on the bottom surface. VGs are small wingtips that are used to produce swirl in the flow stream. In recent years, VGs have been used in vehicle underbody diffusers to delay flow separation and to increase the flow control surface. Meanwhile, setting VGs at the bottom surface may increase the cross-sectional area which creates an increase of the drag force. The focus of this paper is to understand the underbody VG effect on the flow mechanisms downstream of the side-view mirror, and its impact on both drag and down forces. A reduced drag force can eventually increase fuel economy, and vehicle downforce is an essential tool to improve vehicle grip on the road and stability which is particularly important for racing cars. This paper presents an alternative practical solution for improving aerodynamic performance of vehicle side-view mirrors.

 

The turbulent flow behind the side-view mirror is investigated to determine the effects of different VG types, geometries, locations, spacing, and attack angles. Four types of VGs are considered in this work. Changes are made to the baseline model by either adding the VGs close to the frontal edge which aims to control the flow separation, or adding the VGs close to the back edge which aims to reduce the shedding area. Computational Fluid Dynamics (CFD) analysis with ANSYS Fluent is used to simulate the flow behavior by using three dimensional Reynolds-averaged Navier-Stokes method with standard K-epsilon (K-ε) turbulence model. In order to incorporate the effect of vehicle body, each model was assembled on a quad-vehicle bluff body for analysis. The drag and down forces are numerically solved and compared with the results of the baseline model at the speeds of 15, 40, 60 and 80 miles per hour. It is concluded from the CFD analysis that: (1) Mounting VGs at the bottom surface of  side-view mirrors reduced down force in most cases. (2) Setting underbody VGs with certain attack angles at both the front edge and back edge had slight effect on reducing drag force. (3) Setting triangle VGs with 30-degree attack angle near the back edge reduced the drag force by over 6% under high speeds. It also greatly reduced the down force at the same time.


Controlling Drag and Down Forces on a Vehicle Side-View Mirror by Applying Vortex Generator Designs on the Bottom Surface

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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