Windsurfers are divided on the following question: how to put a board on a car, in order to get the less fuel consumption on roads?

The aim of this study is to provide, thanks to aerodynamic considerations, the best configuration for carrying a windsurf board on the roof of a car.
The interest of such a study is to limit the fuel consumption of the car. This consumption is linked to the drag force, which is applied on the system car + board.
Indeed a good aerodynamic behaviour corresponds to a low adimensional coefficient Cd.
In a first time will be considered the car without any board, in order to obtain a reference coefficient, and then to validate the numerical model.
Then two different configurations will be proposed and evaluated. It will be also possible to conclude about the most interesting choice, when carrying a board. And finally, we will highlight the overcost in the Cd, due to the presence of the board on the roof.

We will also try to explain the possible differences between these configurations by qualifying the flow around the car.

To calculate these flows, geometries and meshes have been made with the software called ICEM, and computed with the solver FLUENT3D.