Rate-Based Sensing Concepts for Heat Flux and Property Estimation; and, Transition Detection

Abstract

This paper begins by reviewing recent advances invo lving rate-based sensors for investigating a variety of aerospace heat transfer applications. These investigations include: (a) estimating transient, surface heat fluxes from in-depth sensor s; (b) estimating the location for the onset of transition in high Mach number flows (hypersonic fl ow studies); and, (c) estimating thermophysical properties by in-situ means. A pract ical view to inverse heat conduction is then described pertinent to ground-based studies. Numeri cal stabilization required for the inverse heat conduction study is obtained by (i) interrogat ing the frequency domain of the acquired temperature data; (ii) designing a digital filter t hat preserves accuracy in the time derivative of the temperature; and, (iii) imposing physical const raints generated by the experiment itself. Finally, a brief discussion on the effect of transd ucer lag times, inherent to very short-time studies, is presented. Nomenclature