Accurate and Efficient Rocket Plume Radiative Heat Transfer Predictions

Within the aerospace community, there is need for fast, yet accurate radiation models that can handle a variety of different scenarios, including rocket exhaust. Currently, if solutions are required in a short timeframe, a choice must be made between models with known limitations or very specific operating parameters. A computationally intensive model that is highly accurate may be used only if time is not an issue. The proposed work takes steps to eliminate this dilemma for the aerospace community. By developing a radiation model that can be widely and easily implemented, quick and yet still accurate, the pace of research and development can increase. This will lead to safer, more efficient and less costly designs.

For the past year, research has been conducted to further the accuracy and efficiency of predicting the radiative heat transfer of the rocket exhaust of solid rocket motors at sea level. In particular, the simulated rocket exhaust was from a small solid rocket motor with a throat diameter of 2.535 inches and an exit diameter of 4.875 inches. The rocket was placed five feet above its mounting location on a miniaturized mockup of the mobile launch platform designed for the Ares I rocket, and the rocket exhaust was directed through a scaled-down flame trench.  The purpose was to investigate whether the radiative heat transfer from the rocket exhaust of one vehicle could inadvertently ignite a nearby vehicle.

The objective of the present work is to modify The Discrete Ordinates Model (DOM) to describe radiative heat transfer. The method proposed under the present work consists of moving the discrete ordinates dynamically to produce the effect of having many ordinates with the computational expense of only a few. The idea is instead of having a few fixed ordinates, they will be redistributed dynamically throughout the domain. This will better utilize the available computational resources.

This research will lead to a high-fidelity radiation model for predicting the radiative heat transfer of both liquid and solid motor rocket exhaust. JDOM is comparable to the DO model in terms of computational cost but with a significant increase in accuracy. Cost savings will be realized by having faster computational results, the ability to develop more and higher-fidelity models during the design process and through accurate radiation design loads in the design process.