Investigation of the cooling and underbody flow field on a detailed model scale passenger car. Part 1 - Cooling flows and Reynolds number effects

To decrease the lead time and hence cost for an aerodynamic development programme for a new car model, extended use of down scaled wind tunnel models is one possibility. This however, requires that the models carry many of the exterior, engine bay and underbody details that are present on the full scale counterpart. An important issue in scale testing is to understand the Reynolds number effects that will be present and with an increased detail level of the model it is believed that there will be other Reynolds number effects than on the simplified models that historically have been used. Therefore; the aim of this work is to explain some of the Reynolds number effects that are developed on a detailed model of a sedan type passenger car. The analysis is based on experimental data with both load and pressure measurements as the primary source carried out on a 30% model of a Volvo S60. In the experiment both moving ground and rotating wheels were utilized With the Reynolds number ranging from 8.8e5 to 3.5e6 it was possible to notice interesting Reynolds number effects. The results show that there is a significant Reynolds number dependency of the scale model. However, it is also shown that the Reynolds number dependency is dependent on the detail level of the model