I understand about your standing analogy, but when you mentioned the air that 
just sits there is not as cool as when moving through vents in a bike helmet, 
I imagine you meant in a helmet that did not have vents. When cycling without 
a helmet on your head, the air does blow by. Perhaps the vents in a helmet 
causes the air to blow in within a more narrow profile increasing pressure 
thus blowing harder than not having a helmet.
Richard Glazer
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