Quote:
Originally Posted by akashic
Oh, really... Does there appear to be some rule of thumb regarding the size of such openings or other conditions to suggest when this will happen vs. when significant drag appears?
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akashic,it's a good question and the short answer is,no,I don't have a rule of thumb,although the phenomena appears to be operating at the scale of bedcovers and rear spoilers,fog light openings,turn signal fenestrations,fuselage openings,rear gun turrets,etc..------------------------ With respect to the T-100,the aftbody flow is already established behind the windshield header and A-pillars.Since the flow divergence over the bedcover respects streamline flow,there exists no separation over the entire surface of the cover,save for the portions of the cut-outs. Windtunnel smoke trace or,in my case tuft testing,would reveal circulation within the cut-outs,with the outer flow-field separating at the beginning of the chop,then re-attaching to the trailing part of the chop,just as if it was a solid body. The whole premise of Texas Tech's research on their cab-wing/half tonneau was predicated on this phenomena. General Motors has a US Utility patent utilizing the effect. So a way to answer your question about the size which can effectively be exploited is at least the size of the open bed of a full-size 1/2-ton pickup. Note: I have no empirical data for extended -cab short-bed pickups,as they did not exist in the marketplace during the time of the aero investigations(circa 1988) and remain an unknown quantity to me.