A wind that has a velocity of 8Uand pressure 8p passes a building that can be considered a half cylinder as shown in the following figure. The building’s roof has a radius R and length L (normal to plane shown on figure). The pressure inside the building is pi and the pressure outside on the roof is ps. Assuming that the flow is inviscid, derive an expression for the upward force on the building due to the difference between pi and ps.
In strong winds the force can be quite large. Suppose that a hole is introduced in the building’s roof at point A to make pi equal to the surface pressure there. At what angle ? should hole A be placed to make the net wind force zero?