INVESTIGATING THE EFFECTS OF CROSS WIND ON PASSENGER VEHICLES

THE PATH OF A VEHICLE EXPOSED TO SIDE-WINDS IS DETERMINED BY THE INTERACTION OF ITS AERODYNAMIC AND MECHANICAL CHARACTERISTICS. PART I OF THIS ARTICLE EXAMINES THE AERODYNAMIC ASPECT, FIRST COMPARING THE FLOW PATTERN ROUND AN AEROFOIL AND A VEHICLE AND THE DEVELOPMENT OF THE RESPECTIVE AERODYNAMIC FORCES. THE FLOW PATTERN OVER A VEHICLE EXPOSED TO A SIDE-WIND OF 20 DEG. YAW ANGLE IS DEMONSTRATED BY MEANS OF WOOL TUFTS AND SHOWS HOW THE AIR FLOWS OVER THE VEHICLE ROOF TO EQUALIZE THE HIGH- AND LOW- PRESSURE REGIONS ON THE WINDWARD AND LEEWARD SIDES RESPECTIVELY. THE CENTER OF PRESSURE AND MAGNITUDE OF AERODYNAMIC FORCES ARE COMPARED FOR AEROFOIL AND VEHICLE. SIDE-WIND FORCE COEFFICIENTS ARE SHOWN AS A FUNCTION OF YAW ANGLE FOR THESE VEHICLE GROUPS. THE SIDE-WIND FORCE ON A VEHICLE, AS MEASURED IN WIND-TUNNEL EXPERIMENTS, IS PRESENTED AS A FUNCTION OF VEHICLE SPEED, WITH SIDE-WIND VELOCITY AS PARAMETER. PART II EXAMINES THE EFFECTS OF VEHICLE AND TIRE MECHANICS ON THE CROSS-WIND SENSITIVITY OF VEHICLES. THE MECHANISM BY WHICH THE SIDE-WIND FORCE PRODUCES A YAW VELOCITY OF THE VEHICLE IS EXPLAINED IN TERMS OF FRONT/REAR SLIP-ANGLE DIFFERENCE. THE CORNERING ACCELERATION RESULTING FROM THE YAW VELOCITY INCREASES AS THE SQUARE OF VEHICLE SPEED, GIVEN A FIXED STEER ANGLE, AND A DIAGRAM SHOWS THE REDUCTION IN STEER ANGLE NECESSARY TO AVOID MOMENTARY SKIDDING OF THE VEHICLE. THE RECORDED YAW- VELOCITY/TIME GRAPHS SHOW THAT, UNDER THE CONDITIONS OF THE TESTS, YAW VELOCITY RISES ALMOST LINEARLY WITH TIME, REACHES ITS MAXIMUM AFTER ABOUT 0.4S, AND THEN DROPS OFF SOMEWHAT. WITH REGARD TO THE EFFECTS OF TIRE PARAMETERS, IT IS FOUND THAT THE SO-CALLED SLIP-STEER ANGLE AND HENCE CROSS-WIND SENSITIVITY DEPEND ESSENTIALLY ON THE LATERAL STIFFNESS OF THE TIRES. /AUTHOR/

• Supplemental Notes:
  • Vol 69, No 11, PP 377-381 & NO 12, PP 427-430
• Authors:
  • Grotewohl, A
• Publication Date: 1967-11

Media Info

• Serial:
  • Automobiltechnische Zeitschrift

Subject/Index Terms

• TRT Terms: Acceleration (Mechanics); Aerodynamics; Angularity; Automobiles; Force; Mechanical properties; Speed; Steering; Tires; Tunnels; Velocity; Wind; Yaw
• Uncontrolled Terms: Angles; Parameters
• Old TRIS Terms: Cornering (Vehicle); Flow path
• Subject Areas: Bridges and other structures; Highways; Safety and Human Factors; Vehicles and Equipment;

Filing Info

• Accession Number: 00222702
• Record Type: Publication
• Files: TRIS
• Created Date: May 6 1994 12:00AM