EVALUATION OF ESTIMATION METHODS FOR HIGH UNSTEADY HEAT FLUXES FROM SURFACE MEASUREMENTS

Shock interactions such as those that occur during atmospheric re-entr y can produce extreme thermal Loads on aerospace structures. These int eractions are reproduced experimentally in hypersonic wind tunnels to study how the flow structures relate to the deleterious heat fluxes. I n these studies, the quid jets created by shock interactions impinge o n a test cylinder, where the temperature resulting from the heat flux is measured. These measurements are used to estimate the heat flux on the surface as a result of the shock interactions. Finding the boundar y flux from discrete unsteady temperature measurements is characterize d by instabilities in the solution. The purpose of this work is to eva luate existing methodologies for the determination of the unsteady hea t flux and to introduce a new approach based on an inverse technique. The performance of these methods is measured in terms of accuracy and their ability to handle inherently unstable or highly dynamic data suc h as step fluxes and high-frequency oscillating fluxes. The inverse me thods proved to be the most accurate and stable of the methods examine d.