Development of a New Pressure Measurement Technique and PIV to Validate CFD for the Aerodynamics of Full-scale Vehicles

摘要

In the early stages of aerodynamic development of commercial vehicles, the aerodynamic concept is balanced with the design concept using CFD. Since this development determines the aerodynamic potential of the vehicle, CFD with high accuracy is needed. To improve its accuracy, spatial resolution of CFD should be based on flow phenomenon. For this purpose, to compare aerodynamic force, pressure profile and velocity vector map derived from CFD with experimental data is important, but there are some difficulties to obtain pressure profile and velocity vector map for actual vehicles. At the point of pressure measurement for vehicles, installation of pressure taps to the surface of vehicle, i.e., fuel tank and battery, is a problem. A new measurement method developed in this study enables measurement of surface pressure of any desired points. Also, the flexibility of its shape and measuring point makes the installation a lot easier than the conventional pressure measurement method. In the case of velocity vector measurement, there are two main problems. The first is the measurable domain by PIV is too small for a real vehicle. To solve this, simultaneous multi-camera stereoscopic-PIV that can measure enough size for the wake flow is developed. The second problem is how to validate the flow around the underfloor. For the measurement of such flow, a small probe-type PIV system consisting of a small camera, a laser fiber and a large particle seeder has been developed. By using these validation techniques, the results of RANS and LES are accessed and discrepancies between experimental results are clarified in this paper.