CFD-Based Modelling of the Variation of Aerodynamic Coefficients with Wind Angle

This paper presents CFD-based investigation to develop a deterministic relation between the aerodynamic coefficients and the relative angle of attack of the flow. A mathematical model has been developed to predict the aerodynamic coefficients, which allows accurate quantification of aerodynamic forces and moments for a large variety of ground vehicles in all types of side wind conditions. The vehicle type has been generalised on the basis of primary dimensional parameters of vehicle length, width and height. CFD simulations have been carried on a double deck bus model at wind speed of 25 m/s (90 km/hour, 56 mile/hour), for wind angles ranging from 0º (head wind) to 90º. These computational results have been used for developing systematic equations to quantify aerodynamic coefficients. Conclusions have been based on the requirement of this model in a larger overall stability model for ground vehicles which considers other non-aerodynamic sources of vehicle instability as well. The mathematical relation for aerodynamic coefficients developed herein can be used for numerous other aerodynamic and fluid dynamic investigations that involve large angles of attack.