Aerodynamic Forces on a Triangular Cylinder

Wind tunnel studies have been conducted on flow around an equilateral triangular cylinder mounted with the point upstream. Instantaneous pressure measurements taken around the cross section have enabled a simple picture to be drawn of the pressure perturbations due to the vortex shedding at the rear. Integration of the pressures produces a mean and fluctuating force and moment coefficients. Mean lift and moment coefficients are found to be zero as anticipated from symmetry. Fluctuating lift and moment coefficients occur at the frequency of shedding of a pair of vortices and vary with Reynolds number. The fluctuating drag coefficient is significantly smaller and occurs at double the frequency. Measurements made of the velocity field in the vortex street showed that the velocity and wave length of the street increased downstream and reached a steady state within 10 days.