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Name: Unknown
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: Around 1993
Question:
When you measure drag coefficient, you must obtain dynamic pressure (cm of Hg or water)or g/cm^2. Will the dynamic pressure change if you change the speed. What is the rate of change of dynamic pressure with respects to air velocity (dp/dv)?


Replies:
Well, I am not sure I know exactly what you are asking. The frictional force (which gives a pressure if it is divided by area) caused by air on a moving body has several sources, and its dependenceon speed varies with the geometry of the body, due to turbulence. I think it is usually assumed, for simplicity maybe, that the friction goes as the square of the speed, but that may not generally be valid. Somebody who knows more fluid mechanics or aerodynamics should answer this.

Arthur Smith


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