Mulsanne's Corner: CFD Analysis of endplate effect

CFD Analysis of Endplate Effect

Text and images copyright Emanuele Brandimarti and Cornelis van Steenbergen

Figure 1: Pressure distribution on a rear wing without endplates

In order obtain genuine data on wing endplate effects, CFD analyses have been conducted. Calculations were done for a wing with and without endplates. With endplates attached to the wing, the lift increased by 7%, whereas the total drag increased by 1.4%. This increase is mainly due to the increased friction drag.

Without endplates
First, an analysis of a bare, single element rear wing was done without endplates:

Figure 1: Pressure distribution on a rear wing without endplates.

Figure 2: Pressure distribution on a rear wing with endplates

With endplates
Next, flat endplates with a height-to-span-ratio of h/b = 0.083 were attached:

Figure 2: Pressure distribution on a rear wing with endplates.

The following changes in aerodynamic coefficients were obtained:

Audi R8C minus rear deck
Wing in free air CFD

Applying small endplates will thus result in an increase in the lift generated by the wing by 7 %. The total drag of the wing + endplates has increased by 1.4 %. This is primarily due to an increase of skin friction drag, which has increased by 34 %. The decrease in ‘rest drag’ (pressure drag and induced drag) partially makes up the increase in friction drag, which is just 9% of the total drag in the case of a wing + endplates.

When applying larger, full depth endplates, these endplates will have to be matched properly with the flow around the rear of the car. Simply extending the endplates will cause excessive drag, which can be reduced by means or applying twist to the endplates. This analysis was not done, as the endplate geometry will highly depend on the geometry of the car to which it is applied.