Drag reductions obtained by modifying a box-shaped ground vehicle
NASA Flight Research Center, 1974 - Transportation - 29 pages
Results from a box-shaped vehicle (ref. 15) indicate that substantial differneces sometimes exist between the drag characteristics of highway-sized rolling vehicles and similarly shaped subscale models. In light of these findings, and because high volume box-like shapes are aerodynamically inefficient, further work has been done with modified versions of the vehicle described in reference 15. The modifications consisted of rounding the horizontal and vertical corners of the front of the vehicle, rounding these corners on the rear of the vehicle, sealing the bottom of the chassis with a full-length fairing and then using a 3/4-length underbody fairing. Drag results from these configurations are compared with the reference 15 data for the vehicle with all corners square and vertical corners rounded. Test velocities ranged up to 65 miles per hour and the corresponding Reynolds numbers ranged up to 1 x 107 based on vehicle length. A simple coast-down technique was used to define the drag.
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3/4-length seal Configurations 34 horsepower 60 miles aerodynamic drag coefficient approximately 15 percent base pressure coefficients based on vehicle bottom seal BOX-SHAPED GROUND VEHICLE calibrated speed coast-down method compared with configuration configuration F Configurations With Underbody Cooling vent closed corners for configuration corners rounded data runs deceleration described in reference drag of approximately drag of high drag ref exposed underbody figure 13 flat base Flight Research Center front and rear front suspension system front wheel fuel Full-length seal full-length underbody seal horizontal and vertical maximum Reynolds number miles per hour MODIFYING A BOX-SHAPED motor homes patterns for configurations pounds per square rear wheel reduction in aerodynamic reduction in drag reference 15 rotational inertia rounded corners Rounded Rounded runway sealed for configurations Sealed underbody sheet metal shown in figure square-cornered configuration test vehicle Test velocities ranged tion total drag tractive drag Tuft patterns vehicle length vehicle's vertical corners wheel well seal