The aerodynamic development of the new Audi Q5 (released in 2017) is described. In the course of the optimization process a number of different tools has been applied depending on the chronological progress in the project. During the early design phase, wind tunnel experiments at 1:4 scale were performed accompanied by transient DES and stationary adjoint simulations. At this stage the model contained a detailed underbody but no detailed engine bay for underhood flow. Later, a full scale Q5 model was built up for the aerodynamic optimization in the 1:1 wind tunnel at Audi AG. The model featured a detailed underbody and engine bay including original parts for radiators, engine, axles and brakes from similar vehicles. Also the 1:1 experiments were accompanied by transient DES and stationary adjoint simulations in order to predict optimization potential and to better understand the governing flow. The strong coupling of experimental and numerical tools enabled a best-in-class drag coefficient to be achieved not only for a single optimized vehicle setup but for the majority of four cylinder diesel and gasoline engines in base configuration even in SUV ground clearance (as required for LDT). This is not only true if the vehicle is equipped with the aerodynamically optimized “aero wheel” but also a number of optional rim designs allow comparably low drag values. In order to reach such low aerodynamic drag values, a variety of design and technical measures were necessary. A description of their definition and function is subject of the present paper.
