Electromagnetic Energy Transport Through Complex Media

Abstract

Electromagnetic waves are used in two distinct ways, to transmit information and to carry energy. For aerospace applications, the use of optical methods is excellent for making high fidelity measurements. High temperature flows, such as those found during atmoshperic entry, can also experience significant radiative heat transfer. This energy can lead to added heat loads to vehicles and, in extreme cases, alter the flow chemistry. Radiative transfer can also be affected by the addition of particulate material in the flow. These particles can form optically thick clouds which dramatically affect the flow properties through the process of absorption and scattering.

This work is divided into two principal parts. The first part analyzes the various aspects of radiative transfer in a heated particle laden flow. This includes a summary of methods used to estimate the optical properties of individual particles, as well as the developments to calculate the optical properties of large absorbing particles. This is followed by an analysis of radiative transfer through groups of particles. It is found that the Beer Law can suffer inaccuracies at high particle densities or very fine mesh resolutions. These results are used to develop a Monte Carlo ray tracing (MCRT) framework to analyze the radiative transfer through a particle laden flow, and validate coupled simulations of the system.

The second part of this work discusses hydrogen helium flows at atmospheric entry conditions experienced in the outer gas giants. A non-Boltzmann method to estimate excited states is developed. This is used to analyze chemical models used for computational fluid dynamics (CFD) simulations of these flows and validate them against experimental measurements. It is found that no current CFD chemistry models accurately predict the flow chemistry, likely due to discrepancies in the ionization rate of hydrogen.