Numerical study for flow over a realistic generic model, DrivAer, using URANS

The aim of this study is to present a systematic approach for the grid convergence analysis in simulating flow around a realistic generic model, DrivAer. The numerical simulation is modelled using unsteady Reynolds Averaged Navier-Stokes (URANS) equation. A minimum of three different grid resolutions are considered, which are fine, medium and coarse in order to investigate the grid independency. Richardson extrapolation and Grid Convergence Index (GCI) are introduced to quantitatively evaluate the grid independency. Based on the results between those three different grids, a monotonic convergence criteria has been achieved. The reduction in GCI value indicates that the grid convergence error has been significantly reduced, in which the fine grid has a GCI value less than 7%. Additionally, the result from the fine grid is only 6% difference if compared with previous experimental study

Wind noise simulation of the a-pillar and side view mirror using generic vehicle model, DrivAer

Vehicle interior noise level has now become one of the indicators of driving comfort. However, the generation of noise is a complex phenomenon where it involves various sound sources with different ways of radiation. This research focuses on the generation of wind noise from the A-pillar and side-view mirror of a generic vehicle model known as DrivAer, based on the physical flow behaviour. The main objective of this study is to find the physical flow that causes the generation of A-pillar wind noise and to propose the relation between the A-pillar angles and length of side-view mirror with wind noise generation. This study is conducted numerically at a Reynolds number of Re = 12.17 × 106, with respect to the length of DrivAer model. The noise source is obtained from the incompressible Unsteady Reynolds Averaged Navier- Stokes (URANS); and the noise radiation is predicted using an acoustic analogy based on Curle’s equations. Reliability and validity of the calculations are tested by comparing the basic model with data of experimental studies from previous researchers, whereby the result indicates an almost similar outcome. A total of eight main cases have been studied. These cases include A-pillar cases of varying angles which are 610, 580 (baseline case), 500 and 420; and four side view mirror cases of varying gaps which are 180mm,190mm, 230mm and 240mm. Results have shown that increasing the A-pillar angle makes the sound pressure level louder. 84.33 dB is generated when the A-pillar angle is at 610 and 76.41 dB is generated when the Apillar angle is at 420. The formation of the A-pillar conical vortex formed along the Apillar has been found responsible for the generation of the wind noise. In the case of different side-view mirror position, in which the A-pillar angle remains constant, results for all cases are almost the same according to the A-pillar sound pressure level and sound source level results, in which the noise generated is about 82 dB for all cases of side-view mirror