Some experiments on the fluctuating forces on flat plates in turbulent flow

The report describes experiments te deterrnine the fluctuating drag force on small rectangular flat plates and on rectangular panels of two - dimensional (infinite) flat plates, due to turbulence of relatively large scale and high intensity. The turbulent stream was a two - dimensional jet produced from a slit across a wind tunnel working section. The power spectral densities of the force responses were compared with the velocity spectrum and it is shown that the aerodynamic admittance has a high frequency decline of about 7db. per octave. The root - mean-square values of the fluctuating components of force are shown to decrease with increasing length/width ratio. The probability density functions of the forces and velocity are shown to be nearly Gaussian.