Application Framework for Aero-based Design Optimization of Passenger Cars using NURBS

Abstract

This paper presents a new application framework for aerodynamics-based shape optimization of passenger cars. The rear geometry of a passenger car is the focus of this study due to its significant influence on the aerodynamic characteristics of vehicle. The rear body of a generic car model (the Ahmed body) was represented by Non-Uniform Rational B-Spline (NURBS) curve and NURBS parameters were employed for geometric parameterization. These geometric parameters were systematically modified to alter the geometry using the model developed through a design of experiments process. Computational Fluid Dynamics (CFD) simulations were performed on these geometries to obtain drag coefficients. A polynomial response surface model of drag coefficient was then constructed using linear regression to relate design parameters to the drag coefficient. This response surface model was then used as a starting point for the optimization process. The proposed framework was implemented on a generic notch back car model and the optimized geometric parameters for minimum drag were obtained.