Wind-tunnel boundary interference for V/STOL TESTING

The wake skew angle used in applying the theory of NASA TR R-124 to data correction should be such that the angular deflection of the wake vorticity from the horizontal is one-half that calculated from momentum theory at the lifting element. This usage is in contrast to that of the original paper which used the angle of the mass flow. Because of large-scale recirculation effects, there is a finite lower limit to the test speed at which reliable and correctable data can be obtained in closed wind tunnels. Although a zero-correction wind tunnel for V/STOL testing has not yet been achieved, it is shown that the use of suitably mixed wind-tunnel boundaries can alleviate boundary effects on V/STOL data.