Verification of quantitative infrared thermography heat-flux measurements

Stagnation-point heat flux was measured on 7 half-angle circular cones with spherical nose diameters of 5, 10, and 25 mm using infrared thermography in hypersonic flow. All models were machined from polyether ether ketone (PEEK). A nominal freestream Mach number of 6 with varying initial stagnation conditions allowed for testing at length Reynolds numbers based on nose diameter ranging from 5 x 10(4)-5 x 10(5). Fay & Riddell's theory for calculating heat flux at the stagnation point provided a comparison to verify experimental data-reduction methods. Excellent agreement was obtained. Sources of deviation were investigated and best practices for obtaining heat-flux values most similar to theory are presented. Heat flux calculated using a one-dimensional assumption had a mean error of 8.9% from the theoretical expectation. To improve upon this, an implicit, finite-difference approximation was used to solve the axisymmetric heat equation in spherical coordinates, assuming a known surface temperature and isothermal back face. The axisymmetric calculation yielded steadystate heat-flux magnitudes 1-10% greater than the one-dimensional approach, as expected. Correcting for longitudinal heat transfer yielded heat fluxes more nearly proportional to 1/root D, and the mean error decreased to 4.8%.