The Aerodynamics of a Small Car Overtaking a Truck

Abstract

A more ambitious dynamic experiment was undertaken by Brown and Seeman,[6], using models catapulted along parallel tracks and passing a crosswind generator. Spacing between vehicles and relative velocities, including vehicles passing in opposite directions could be represented. The shape of the ABSTRACT The influence of a large truck on the aerodynamics of a small passenger car in an overtaking manoeuvre on the motorway was considered, many years ago, during the 1970's, to be a potential problem for the vehicle aerodynamicist. The concern never became significant as vehicle architecture evolved and car weights increased. The current drive for improved fuel economy is advocating that a considerable reduction in vehicle mass is desirable and therefore it may be time to readdress the significance of the truck passing manoeuvre. A quasi-steady experiment has been undertaken at small model scale to examine the aerodynamic characteristics of a small car in proximity to a large truck. Measurements at yaw were included to crudely simulate the effects of a crosswind. The wind tunnel data is presented and the limitations of the experimental procedure are discussed. An estimate of the increased aerodynamic input on a car in a real world overtaking manoeuvre with relative velocity between the two vehicles is introduced. The data is compared with the steady state yaw characteristics of the car alone to relate truck passing with the general concern of crosswind sensitivity. Under the same crosswind conditions the truck passing manoeuvre is shown to be a more extreme, but rarer event.

Aerodynamic drag change of simplified automobile models influenced by a passing vehicle

“…The drag increased when the truck model was near the rear end of the vehicle model. This trend qualitatively agrees with the previous researches using the five times longer truck (Howell et al, 2014) and the same size vehicle (Noger et al, 2005) as the passing vehicle. Then, the trend of C D base at each relative position qualitatively agrees with this general trend of C D .…”

“…Many studies have explored the components of the flow field that likely affect aerodynamic stability, including the pressure field of the passing vehicle (Howell et al, 2014;Noger et al, 2005;Uystepruyst and Krajnović, 2013), the crosswind from the passing vehicle (Gilliéron, 2003;Howell et al, 2014), and other factors (e.g., the Venturi effect at the narrow gap between the two vehicles; Clarke, 2007;Yamamoto et al, 1997). To systematically summarize the contribution to the drag change in consideration of these components, we used the following procedure.…”

Coupled analysis of the unsteady aerodynamics and multi-body dynamics of a small car overtaking a coach

“…In the wind tunnel experiments, the quasi-steady overtaking experiments revealed that the loads increased under cross winds when the overtaking car was on the lee side of the overtaken vehicle. 2,3 The study by Noger and Van Grevenynghe 4 researched the transient aerodynamic force responses associated with quasi-steady aerodynamic loads acting on the overtaken vehicle when a heavy truck and a light vehicle are in the overtaking maneuver. In addition, the unsteady overtaking experiments were researched.…”

Coupling analysis of transient aerodynamic and dynamic response of cars in overtaking under crosswinds

“…A car-truck overtaking wind tunnel test indicated that the pressure field around CONTACT Yiping Wang wangyiping@whut.edu.cn the front of a truck greatly influences the forces experienced by the overtaking car, and the influence is mainly dependent on the truck velocity. The dynamic changes in the side force and the yaw moment are also important concerns (Howell et al, 2014;Noger & Grevenynghe, 2011). A further wind tunnel test also revealed the influence of velocity ratio between the two overtaking vehicles on their aerodynamic performance (Telionis et al, 1984;Yamamoto et al, 1997).…”