Introduction to Flight 7th Edition by John Anderson

Exercise 9

Consider a flat surface in an aerodynamic flow (say a flat sidewall of a wind tunnel). The dimensions of this surface are 3 ft in the flow direction (the x direction) and 1 ft perpendicular to the flow direction (the y direction). Assume that the pressure distribution (in pounds per square foot) is given by p = 2116 - 10 x and is independent of y. Assume also that the shear stress distribution (in pounds per square foot) is given by ? w , = 90/( x + 9) 1/2 and is independent of y as shown in figure below.

In these expressions, x is in feet, and x = 0 at the front of the surface. Calculate the magnitude and direction of the net aerodynamic force on the surface.