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Forces due to turbulent flow do not vary directly as the velocity of the air past the plate, but at a much higher rate. If the velocity is doubled, the plate not only meets with twice the volume of air, but it also meets it twice as fast. The total effect is four times as great as in the first place. The forces due to turbulent flow therefore vary as the square of the velocity, and the pressure increases very rapidly with a small increase in the velocity. The force exerted on a plate also increases directly with the area, and to a lesser extent the drag is also affected by the shape and proportions. Expressed as a formula, the total resistance (D) becomes: D = KAV², where K = co-efficient of resistance determined by experiment, A = area of plate in square feet, and V= velocity in miles per hour. The value of K takes the shape and proportion of the plate into consideration, and also the air density.
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Aspect Ratio
EFFECTS OF ASPECT RATIO ON FLAT PLATES.Aspect Ratio. Length/WidthResistance K as a Multiple of a Square Plate.1.00 (square)1.001.501.042.001.053.001.074.001.085.001.096.001.107.001.129.001.1410.001.1515.001.2620.001.3430.001.40Solution