Mapping Transition on a Hypersonic Vehicle Using Experimental Surface Pressure and Heat Transfer Data

The comparison of CFD predictions with aerodynamic heating data must be preceded by a careful analysis of the experimental data. Of primary interest is the location of transition since boundary layer state is still a user input for most CFD codes and an error here can result in large variations between the numerical and experimental results. Transition can usually be located by observing the associated sharp rise in surface heating rate with increasing Reynolds number. However, on complex vehicles the distributions of laminar, transitional, and turbulent flow will also be complex, and a rise in heating rate may be produced by flow phenomena other than transition. This paper reviews the method used to determine boundary layer state using experimental surface pressure and heat transfer data. It is shown that more accurate maps of the transition fronts may be obtained if classical incompressible transformations are applied to the wind tunnel database before Stanton-Reynolds number correlations are made. This transformation improves general data correlation and helps identify areas where flow phenomena other than transition affect the level of heating.