Abstract
Flow around the front-pillar of an automobile is typical of a flow field with separated and reattached flow by a longitudinal vortex system. The longitudinal vortex system causes the greatest aerodynamic noises around a vehicle. This paper describes the control of the longitudinal vortex induced around the front pillar of actual vehicles, based on clarification of the vortex generation phenomena, although the final objective of the study is to reduce the greatest aerodynamic noise sources as caused by a longitudinal vortex system over 100km/h. The paper focuses on the control of longitudinal vortex system associated with the aerodynamic noise. The first step is to clarify how a longitudinal vortex system will be produced. For that purpose, a delta wing was employed easily as a compact model to produce longitudinal vortex and to obtain the clue to generation of the vortex. The longitudinal vortex was visualized experimentally with dye in a water tank. Using STAR-CCM + as a CFD software for the delta-wing, the longitudinal vortex was reproduced numerically. The characteristics of the longitudinal vortex were analyzed. Based on the findings on the vortex system, some protuberances were considered to weaken the strength of the vortex system from the standpoints of both their locations and their configurations. The second step is to apply the knowledge obtained from the delta-wing flow analyses to actual vehicles. Knowledge regarding the protuberances was employed to determine the location and configuration of a side-view mirror for actual vehicles. It was found that one concept of the control of the longitudinal vortex system is to provide the vortex system with the airflow from the strong separated flow given by optimizing the shape of a side-view mirror. Sufficient supply of airflow at the tip of the longitudinal vortex system tends to weaken the longitudinal vortex system.
