RAPRAL v1.0: RAdiation Prediction using RAy tracing and Line-by-line methods for hypersonic air flows

TL;DR

RAPRAL v1.0 is a C++-based radiation solver that combines line-by-line spectral modeling with ray tracing to accurately simulate radiative processes in hypersonic air flows.

Contribution

It introduces a detailed, integrated approach for spectral and spatial radiation modeling in hypersonic flow simulations, validated against established codes.

Findings

Accurately captures spectral features across various conditions.

Provides reliable predictions of radiative heat flux in hypersonic flows.

Demonstrates robustness in simulating radiative processes in high-temperature air flows.

Abstract

A new radiation solver, RAPRAL (RAdiation Prediction based on RAy tracing and Line-by-line) implemented in C++, is developed for simulating high-temperature thermochemical nonequilibrium radiative processes. RAPRAL integrates detailed line-by-line spectral modeling with a ray-tracing solution of the radiative transfer equation, enabling accurate resolution of both spectral features and spatial radiation transport. The adopted methods and their implementation are described in detail. To assess the overall capability and accuracy of RAPRAL, we first focus on the computation of atomic and molecular bulk spectral coefficients. Through comparison with the established code in the literature, RAPRAL demonstrates its ability to accurately capture key spectral features across a wide range of conditions. Moreover, RAPRAL is applied to predict afterbody radiative heating in the Fire II flight experiment, based on a two-temperature, 11-species air flowfield. The results demonstrate that the present approach provides reliable predictions of radiative heat flux and effectively captures the dominant radiation mechanisms. Overall, the presented results demonstrate that RAPRAL is a robust tool for simulating radiative processes in hypersonic air flows, and future versions will extend its capabilities to include species relevant to planetary atmospheres.