Analysis of Cold/Hot Spot Effect in Flight Test Heat Flux Measurement

Abstract

In model flight tests, the cold/hot spot effect often occurs due to the difference in thermal response between the heat flux sensor and surrounding thermal protection materials, which affects the heat flux measurement. In severe cases, the measurement deviation may even exceed 100%. This article analyzes the flight data of the space model flight test MF-1 and finds that there is a significant hot spot effect. This paper reproduces the temperature measurement process of MF-1 thin-skin structure along the trajectory through aerodynamic thermal/heat transfer coupling calculations. The difference between the flight data and the coupling calculation results is compared and analyzed. Based on the flight test of MF-1, the formation mechanism of the cold/hot spot effect and its impact on wall heat flux are studied. It is found that local temperature discontinuities can generate an additional wall-normal velocity near the wall, which will generate an additional wall-normal convective heat transfer, further increasing the measurement deviation of wall heat flux. The research results of this paper have important guiding significance for the development of heat flux sensors for aerospace model flight tests and correctly conducting heat flux measurements.