Turbulence Effects on Drag of Sharp-Edged Bodies

Contrary to popular opinion, wind tunnel tests showed that the drag coefficient of angular shaped bodies is significantly affected by the intensity of the free stream turbulence. For some bodies an increase in intensity causes an increase in C_D while for others a decrease in C_D results. Tests made on a vibrating body having a shape similar to an H beam showed that the amplitude of vibration was increased more than 200% with an increase in free stream turbulence. The change in coefficient of drag C_D is attributed to two primary effects. The first is increased Reynolds stress in the region of the surface of separation which appears to cause an increase in C_D and the other is reattachment of the flow to the body which may cause the C_D to increase or decrease depending upon the shape of the body. The range of Reynolds numbers in these tests is limited to the relatively narrow span from approximately 5 x 103 to 7 x 104.