Heat-transfer measurements in hypersonic flow using luminescent coating techniques

The development and application of high-speed imaging and luminescent coating techniques to measure full-field surface heat-transfer rates in short-duration hypersonic flow is presented. Tests were performed on an indented cone model at the 48-in. shock tunnel and the LENS I tunnel facilities at Calspan-University of Buffalo Research Center. Nominal test conditions ranged between Mach numbers of 9.5 and 11.1 and Reynolds numbers of 1.4 x 10(5) and 3 x 10(5) m(-1) with run times of less than 10 ms. Processed submillisecond images show the three-dimensional, time-dependent development of the embedded separated flow and shock/boundary-layer interaction into a steady axisymmetric structure bounded by regions of laminar flow. Conversion from processed image data to full-field heat-transfer measurements were performed using both an in situ calibration with thin-film platinum heat-transfer gauges as well as an a priori temperature calibration and transient heat-transfer theory. In situ calibrations displayed excellent correlation with surface-mounted gauges, whereas a priori calibrations showed a larger susceptibility to bias errors.