Evaluating Shock-Tube Informed Biases for Shock-Layer Radiative Heating Simulations

摘要

A methodology for directly informing flight vehicle radiative heating simulations based on shock-tube measurements is developed. The differences between these shock-tube informed (STI) radiative heating values and the corresponding nominal values are typically the dominant contributor to the radiative heating margin. Previous approaches for evaluating the STI radiation were limited to the stagnation-point radiative flux, assumed optically-thin adjustments to the radiative flux, and were limited to tangent-slab radiation transport. The present approach removes these limitations. This approach relates differences between shock-tube measurements and their nominal simulations to the upper level number density of individual radiative processes. These upper level number density differences are compiled as a function of time behind the shock for all relevant shock tube measurements. By tracing the streamline from a point in a flight vehicle flowfield back to its crossing of the bow shock, the normal shock velocity and flow time since the shock are determined for that single flowfield point. This streamline tracing is repeated for all points in the flowfield computational grid. These normal shock velocities and times since the shock are used to evaluate the previously compiled differences in the upper level number densities of radiating species. These differences are applied during the radiation calculation to obtain the shock-tube informed bias to the radiative heating. Through the streamline mapping, the entire flowfield may be treated, which enables the use of ray-tracing radiative heating simulations and allows off-stagnation point surface regions to be considered. By adjusting the upper level number density prior to the radiative transport evaluation, the impact of optical thickness is captured. This approach may be automated within a flowfield and radiation code to enable routine analyses of the shock-tube informed biases. Examples of this capability are demonstrated for Titan and Earth entry cases.