Improving MuSES EO/IR target and background scene simulation accuracy with the RapidFlow fluid solver

Document Type

Conference Proceeding

Publication Date

10-29-2025

Abstract

The ability to accurately predict spectral signatures of targets in outdoor scenes is an important capability for defense agencies, for both target acquisition and detection avoidance efforts. In thermal infrared (IR) wavebands, temperature is a primary contributor to remotely-sensed radiance. Consequently, enhancements to the accuracy of thermal predictions are valuable, with estimates of convective heat transfer being a source of uncertainty where improvements can be realized. One standard method of convective heat transfer calculation employs a global speed-dependent convection coefficient for all exterior surfaces. This approach efficiently predicts convection coefficients for large scenes with dynamically changing wind conditions. Frequent changes in wind speed and direction tend to negate the weaknesses of this simplistic approach (e.g., lack of localized wake and flow acceleration), and numerous thermal and IR validations of MuSES performed in the past bear this out. For some simulation applications however, additional thermal fidelity is required. Traditional computational fluid dynamics (CFD) codes provide ample spatial fidelity, typically with a significant computational cost. A fully-transient diurnal analysis of an outdoor scene would likely be infeasible given the large spatial and temporal scales typically of interest. We present here a flow solver designed specifically for infrared prediction applications. This flow solver represents air flow at an appropriate spatial resolution level for accurate simulation of convective heat transfer in the context of IR scenes. Predicting the geometry-induced location of flow accelerations, wakes, and advective flow is sufficient for calculating convection with acceptable accuracy for thermal EO-IR predictions. The accuracy of this new flow solver greatly improves upon the use of a universal wind speed-dependent (but directionless) convection correlation for entire scenes without all the drawbacks of traditional CFD solutions. Application-specific simplification of the flow equations allows this flow solver to be fast and robust, requiring minimal user effort and fluid domain expertise.

Publication Title

Proceedings of SPIE the International Society for Optical Engineering

ISBN

[9781510692855]

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