FSAE Front Wing & Bluff Body Diffuser CFD Study

Objective: Using Star CCM+ investigate the aerodynamic performance of a Formula SAE front wing

An investigation and analysis of a front wing in ground effect is presented utilizing STAR CCM+. Studying the effects of ride height variation has on the performance of the wing and how it is affected by the addition of a rotating wheel at a fixed ride height.

Providing insight on determining a height of maximum downforce for the wing, its effect on other aerodynamic devices, and the ride height sensitivity. Simulations of the front wing incorporated a moving ground, and rotating wheel to simulate the real world scenario of an open wheeled racecar.

Post processing of results included utilized plots of pressure coefficients and accumulated force with the addition of line integral convolution and scalar scenes. This showed the optimal height where maximum downforce is produced by the wing to be between 25.4 mm and 38.1mm, with the addition of the rotating wheel there was a 55% reduction in CD and CL but being the most efficient coming in at 6.07.

STAR CCM+ meshed front wing with tire model

Wall shear stress under the wing for varying ride heights

Pressure coefficient distribution along the span of the lower surface of the main plane.

Accumulated force through the span of the wing

Front view of the vorticity scale 0.1m behind the front wing

Objective: Compare data obtained from a wind tunnel bluff body diffuser to CFD data using Star CCM+.

The comparison of the numerical and experimental bluff body diffuser performance at a ride height of 10 mm of varying angles from 0-17 degrees showed to have similar trends in the pressure generation under the body but large error.

The CFD results showed that the diffuser performance improves with higher angles leading up to 17 degrees, however the wind tunnel results say otherwise. The greatest performance at 10 mm ride height is at 9 degrees. As the diffuser angle gets larger, the local pressure gradient at the inlet becomes more severe resulting in separation and a decrease in total pressure (Jowsey, L. and Passmore, M, 2010).

The main reason for the large error is due to the fact that the pressure inlets are not flush with the surface. This influences the airflow at these regions and from data seems to over estimate the pressure generated.