Application of a Monte Carlo Technique to Model Helicopter Plume Reflections

Abstract : High fidelity infrared signature modelling of targets requires the accurate representation of not only factors concerned with the target itself but also the immediate environment. Modelling of multiple reflections from extended thermal sources can often be oversimplified, partly due to the complexity of the problem and the resulting intensive processing requirements. The use of Monte Carlo ray tracing techniques for reflection modelling is a documented approach. Insys Ltd has developed a code, McCavity, on behalf of Dstl based on these techniques, to quantify various aspects of the multiple reflections problem to the infrared signature. This paper reports on the use of McCavity for the assessment of reflections arising from an exhaust plume onto a representative helicopter tail-boom and static rotor structure. A simple, generic, example is used to show that the contribution of reflections from an extended source to the infra red signature can be significant. McCavity code validation against standard published results is also presented.