Development of “Aero Slit” - Improvement of Aerodynamic Yaw Characteristics for Commercial Vehicles

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Development of “Aero Slit” - Improvement of Aerodynamic Yaw Characteristics for Commercial Vehicles

Sumitani, Keiji / Yamada, Minoru

To reduse crosswind sensitivity, the yaw moment should be decreased under both transient and steady conditions. The transient condition is when a vehicle comes out immediately from a tunnel into a crosswind while the steady condition is when driving straight along the coastline. After studying the pressure distribution and the flow pattern around the body, we have reached the ideal air flow at the front-side corner that reduces the yaw moment under both conditions. And we have devised an entirely new method to achieve this better air flow. The method uses an internal flow generated by a pressure difference in the flow feeld to create a jet effect and by using only a duct for internal flow to control the outside air flow. It is done without any change to the exterior styling, except at the flow exit. We call it “Aero Slit”.This “Aero Slit” is effective only under crosswind conditions, and does not increase aerodynamic drag when a crosswind is not blowing.In applying this method to a production vehicle, we have found some interesting flow characteristics. We will describe them herein.After applying it to the TOYOTA LITEACE, both the maximum yaw rate and the lateral deviation in crosswind have been improved by 15 percent.