Theoretical Study of Flaps for Reducing Aerodynamic Drag of Trucks

Abstract

Chapter 1 will give a basic explanation of the energy losses for a truck following by a more detailed explanation of the aerodynamic effects experienced at highway speed. After that, there is a brief reminder of the different technologies used to reduce the aerodynamic drag. Finally, an introduction to the subject which will be treated in this work, an add-on devices to reduce the drag at the rear of the trailer.

Chapter 2 will defined the main constraints to take into account for the conception of a such device. A section will be dedicated to the future European legislation for add-on aerodynamic devices used on trucks. And an other will be focused on the add-on devices at the rear of the truck.

The third chapter of this thesis will present the different assumptions made to model the rear of the truck with such devices. A part of this chapter will also be dedicated to the equations used to resolve the flow and the main parameters which have to be imposed, such as the viscosity of the flow. The second part of this chapter will concern the software used, OpenFoam, and the implementation of the model such as the meshing method and the turbulence implementation.

Then, the chapter four will treat a study made by the Von Karman Institute for Fluid Dynamic on behalf of AIRWIN. This study was a shape optimisation of a flap in order to find the minimal drag achievable. One of the goal of this work was to calibrate a CFD model in terms of sensitivity and accuracy with the theoretical and experimental results of IVK to push the simulation further. Once the model obtained, the study will be focused on the influence of an irregularity on the trailer before the flap followed by a study of the influence of an offset.

Chapter five will present an alternative to the design studied by the Von Karman Institute which becomes inexploitable for AIRWIN due to the changes in the European legislation . This design offers several advantages, namely increased robustness and a better comfort for the driver. This chapter will also compare this solution with market competitor produces.

Then the last chapter will be focused on the optimisation of the alternative solution proposed by AIRWIN to improve its efficiency in terms of drag reduction.