Project Plan and Objectives

            The drag force contributors that can be most readily varied through the design of the tractor and trailer are those affecting the form drag and induced drag. This project aims to determine the effect that two of a tractor-trailer’s distinctive attributes have on these drag forces and to make recommendations to minimize any detrimental effects.

            The pressure differential that causes form drag is, on a vehicle as large as a tractor trailer, generally substantial enough that other drivers can (although dangerously and illegally) occasionally move very close behind the trailer and take advantage of the large low pressure area. The high pressure zone at the front of this driver’s vehicle experiences a pressure drop, thereby reducing the form drag on his vehicle and the tractor trailer (at the cost of increasing risk of a serious accident).

            The form drag of the tractor-trailer can be reduced by allowing air to flow more easily over the vehicle. This can be accomplished by creating a sleek frontal shape, which is often done by extending the slope of the windshield. The simplest method, however, of improving a vehicle’s aerodynamics with respect to form drag, is to reduce the cross sectional area. Consequently, the goal of the project should be to prove the detrimental effect of unnecessary trailer height, which is the most practical avenue for altering the tractor-trailer’s cross sectional area.

             A relatively unique feature of tractor-trailers is the detachability of the trailer. The trailer typically attaches to the tractor via a fifth-wheel assembly, leaving a sizeable gap between the trailer and the cab of the truck. This gap is a potential aerodynamic weakness. Air could flow into the gap and create a high pressure zone, ultimately sabotaging any smoothing designs used before it. The goal of the project should thus also be to determine the effect of cab-trailer distance on the drag.

            Lastly, the project should be able to make recommendations for the design of future tractor-trailers. It should evaluate the effectiveness of two new accessories aimed at reducing the drag; a flexible cab-trailer sleeve and an aft-end balloon. The final recommendations should take into account the results of the testing on the height, the cab-trailer gap and the two proposed accessories.

In summation, the goals of the project will be to:

Click here to move on to the Engineering Overview page.