Soft Computing Model for Inverse Prediction of Surface Heat Flux from Temperature Responses in Short-Duration Heat Transfer Experiments

Aerodynamic experiments in high speed flow domain mainly rely on precise measurement transient surface temperatures and subsequent quantification of heat flux. These experiments are mainly simulated in high enthalpy short-duration facilities for which test flow duration are in the order of few milliseconds and the thermal loads resemble the nature of step/impulse. This study focuses on a specially designed fast-response coaxial surface junction thermal probe (CSTP) with capability of capturing transient temperature signals. The short-duration calibration experiments are realized to mimic the simulated flow conditions of high enthalpy test facilities. The classical one-dimensional heat conduction modelling has been used to deduce surface heat flux from the acquired temperature responses. It demonstrates a commendable accuracy of 2.5% when compared with known heat loads of calibration experiment. An advanced soft computing technique, the Adaptive Neuro-Fuzzy Inference System (ANFIS), is introduced for short-duration heat flux predictions. This methodology successfully recovers known (step or ramp) heat loads within a specific experimental time frame (0.2s). The results exhibit excellent agreement in prediction of trend and magnitude, carrying uncertainties of 3% for radiative and 5% for convective experiments. Consequently, the CSTP appears as a rapidly responsive transient heat flux sensor; for real-time short-duration experiments. The soft computing approach (ANFIS) offers an alternative means of heat flux estimation from temperature history irrespective of mode of heat transfer and nature of heat load, marked by its prediction accuracy, diminished mathematical intricacies, and reduced numerical requisites.