Assessment of conventional and air-jet wheel deflectors for drag reduction of the DrivAer model

Abstract

Aerodynamic drag is a large resistance force to vehicle motion, particularly at highway speeds. Conventional wheel deflectors were designed to reduce the wheel drag and, consequently, the overall vehicle drag; however, they may actually be detrimental to vehicle aerodynamics in modern designs. In the present study, computational fluid dynamics simulations were conducted on the notchback DrivAer model—a simplified, yet realistic, open-source vehicle model that incorporates features of a modern passenger vehicle. Conventional and air-jet wheel deflectors upstream of the front wheels were introduced to assess the effect of underbody-flow deflection on the vehicle drag. Conventional wheel-deflector designs with varying heights were observed and compared to 45∘ and 90∘ air-jet wheel deflectors. The conventional wheel deflectors reduced wheel drag but resulted in an overall drag increase of up to 10%. For the cases studied, the 90∘ air jet did not reduce the overall drag compared to the baseline case; the 45∘ air jet presented drag benefits of up to 1.5% at 35 m/s and above. Compared to conventional wheel deflectors, air-jet wheel deflectors have the potential to reduce vehicle drag to a greater extent and present the benefit of being turned off at lower speeds when flow deflection is undesirable, thus improving efficiency and reducing emissions.

Investigation of the effect of the use of top deflectors on aerodynamic performance in vehicles with CFD analysis

“…As a result of their research, they found that conventional wheel deflectors only reduced wheel drag but increased overall drag by close to 10%. They found that air-jet wheel deflectors, on the other hand, reduced drag by up to 1.5% at velocities of 35 m/s and above [8]. Khosravi et al [9] investigated the effects of the use of deflectors and cabin blades on heavy commercial vehicle drag.…”

An Exploratory Wind Tunnel Study of Air Jet Wheel Spoilers

“…Wolf [7] has shown that using the airflow ducted from front-mounted heat exchangers and deflected vertically downwards forward of the front wheels had a benefit on the 1997 model of the Porsche 911, although the improvement in drag coefficient was not quantified. Two recent CFD studies conducted by Nabutola and Boetcher [8,9] to investigate air jet wheel spoilers on a simplified body and a DrivAer model concluded in both cases that there were no drag benefits available.…”