Correlation of freestream pressure disturbances in supersonic wind tunnels

An attempt is made to correlate data for freestream disturbance levels in terms of parameters that can be easily calculated for most wind tunnels. A correlation expression is derived assuming that the fluctuating pressure at the wall of the supersonic wind tunnel are related to fluctuating pressures in the freestream. The acoustic origins, flow properties, and geometric factors are taken into account. The suggested correlations of wind tunnel disturbances provide good predictions of rms pressure disturbances in the freestream of wind tunnels or on the surface of cones at Mach numbers greater than 2.5.