Munson, Young and Okiishi's Fundamentals of Fluid Mechanics, Binder Ready Version
8th Edition
ISBN: 9781119080701
Author: Philip M. Gerhart, Andrew L. Gerhart, John I. Hochstein
Publisher: WILEY

#### Videos

Question
Chapter 1.2, Problem 1P
To determine

## The dimension of coefficient of drag.

The drag coefficient CD is dimensionless.

### Explanation of Solution

Write the expression for the wind force (F).

F=CDρV2A2                                                (I)

Here, drag coefficient is CD, density of air is ρ, velocity of air is V, cross-sectional area of the building is A.

Conclusion:

The equation (I) can be rearranged to get CD as follows:

CD=2FρV2A                                                 (II)

The dimensions of the various terms in the equation (II) are given by:

F=MLT2ρ=ML3V=LT1A=L2

Substitute the above in equation (II) to get the dimensions of CD.

CD=MLT-2(ML-3)(LT-1)2(L2)CD=MLT-2(ML-3)(L2T-2)(L2)CD=M0L0T0

Thus, the drag coefficient CD is dimensionless.

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