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The effect of Cross-Flow Vortex Trap Devices (CVTDs) on the local flow field and vehicle drag at a range of yaw angles has been investigated in wind tunnel experiments. The CVTD is a flow control device proposed by Bauer and Wood that aims to reduce the sensitivity of articulated road haulage vehicles to crosswinds by managing the tractor-trailer gap cross-flow. A 1/10th scale model is used in a low-speed wind tunnel at a Reynolds number of 900,000. The aerodynamic drag force is measured using a load cell connected to a rotating, raised ground plane. This research also uses tuft flow visualization to examine the local flow fields and pressure taps to determine trailer pressure distributions. It is found that a configuration of four 45% length CVTDs reduces the wind-averaged drag coefficient by 12%.

The turbulent wake behind a truck is responsible for a considerable proportion of the total aerodynamic drag. There is evidence to suggest that the underbody flow affects the wake topology, although this interaction is not well understood. Typical truck trailer underbodies are geometrically very complex and have a range of bluff bodies - such as the wheel and axle assembly, structural beams or the secondary fuel tank for refrigerated trucks - attached. These components block the underbody flow and erode its momentum. However, most of the previous studies of the wake flow have used models with clean underbodies. It is thus uncertain whether the wake shapes found by these studies accurately represent the wake topology behind a real truck with a detailed underbody.