Analytic extrapolation to full-scale aircraft dynamics

Abstract

T extrapolation from subscale wind-tunnel data to fullscale flight becomes an especially serious problem at subsonic speeds when stall is involved and at high subsonic and transonic speeds where shock boundary-layer interaction can dominate the aerodynamics. In the case of dynamic testing, valid subscale simulation is often impossible, because the coupling existing in full-scale flight between the location of the free (unfixed) boundary-layer transition and the airfoil motion has been changed drastically, if not eliminated completely, through the use of a tripping device. One solution to this scaling problem is to supply ground testing facilities with the capability of simulating full-scale Reynolds number. Tunnels with such capability are available,' and others will undoubtedly become available. However, they will all be in too much demand to be able to accommodate all of the development testing. In spite of progress being made in computational fluid dynamics, no one is presently ready to forecast when simulation of the coupling between boundary-layer transition and vehicle motion will be possible. A way out of this preliminary design dilemma is to extrapolate analytically from subscale test data to predict the full-scale aircraft dynamics. The analytic approach is as follows: 1) Establish analytic relationships between dynamic and static aerodynamic characteristics induced by viscous flow effects. 2) Prove the veracity of the analytic method by predicting dynamic test results using corresponding static test data at the same subscale flow conditions. 3) Determine the effect of Reynolds number on static aerodynamic characteristics.