Heat Flux Data Reduction using a Natural Filter Test Function

摘要

This paper presents (ⅰ) a new preconditioned data reduction formulation; and, (ⅱ) enhanced thin-film temperature gauge model for estimating the source heat flux applicable to impulsive test facilities used in hypersonic test programs. In such short-time tests, the heat flux is recovered from an active temperature sensitive thin-film. The physical situtation permits a constant property, semi-infinite substrate heat conduction model to be formulated relating the net substrate heat flux to the thin-film interface. Conventional lumped models assume no volumetric effects in the thin-film. An enhanced boundary condition (interfacial energy balance) for the substrate is proposed that includes the storage of energy in the thin-film. There are cases where the product of thin-film properties (density and specific heat), thickness and time rate of change in the thin-film temperature should not be neglected. This additional term does not introduce additional mathematical complexity. A parameter-free, physically-motivated preconditioner is introduced to the integral equation system. This mathematical operation increases predictive stability and accuracy. This concept is applied to both the conventional and enhanced thermal models for predicting the source heat flux. A future-time method is proposed as the regularization scheme. The optimal future time parameter is identified using a thermal phase plane. The preconditioner is shown to strongly influence the development of patterns that allow for the identification of the optimal regularization parameter in the thermal phase plane. Highly favorable results are demonstrated for the simulated data sets in the presence of random noise.