An Estimation of the Effect of Turbulence from the Natural Wind and Traffic on the Cycle-Averaged-Drag Coefficient.
2022-01-1076
03/29/2022
- Event
- Content
- A drag coefficient, which is representative of the drag of a car undergoing a particular drive cycle, known as the cycle-averaged-drag coefficient, has been previously developed. It was derived for different drive cycles using mean values for the natural wind. It assumed terrain dependent wind velocities based on the Weibull function, equi-probable wind direction and shear effects. It did not, however, include any effects of turbulence in the natural wind. Some recent research using active vanes in the wind tunnel to generate turbulence has suggested that the effect on drag can be evaluated from the quasi steady wind inputs. On this basis the effect of natural wind turbulence on the aerodynamic drag of a typical car has been obtained as a function of car velocity and both wind velocity and direction. For a particular combination of car and wind velocity the additional effects of turbulence are very sensitive to the wind angle and on the shape of the drag curve with yaw angle. The wind averaged drag coefficient is found to be uniquely dependent on the car velocity and the mean velocity and turbulence intensity of the wind. The effect of incorporating turbulence on the cycle-averaged-drag coefficient has then been determined for a large range of different car types. The drag is always increased by the turbulence but in all cases is relatively small, but not ignorable.
- Citation
- Howell, J., and Passmore, M., "An Estimation of the Effect of Turbulence from the Natural Wind and Traffic on the Cycle-Averaged-Drag Coefficient. ," SAE Technical Paper 2022-01-1076, 2022, .