Multiscale Hybrid CFD/DSMC Simulation of Rocket-Induced Atmospheric Waves for Ionospheric Disturbance Prediction

Abstract

Rocket exhaust plumes at high altitude generate acoustic and gravity waves that propagate into the ionosphere as traveling ionospheric disturbances (TIDs).We previously developed a one-way-coupled, two-dimensional (2D) axisymmetric hybrid Computational Fluid Dynamics (CFD)/Direct Simulation Monte Carlo (DSMC) framework for a Falcon 9 FT second-stage plume, reproducing the bow shock, inner shock, mixing layer, and exhaust core [3]. However, the 2D axisymmetric framework could not represent the gravitationally stratified thermosphere or the resulting asymmetric wave propagation associated with TIDs. Here, we extend the framework to three dimensions by coupling the existing 2D CFD and DSMC solutions, through a purpose-built converter, to a large-scale, gravitationally stratified 3D DSMC domain initialized using the NRLMSIS 2.0 empirical atmosphere. A dual-resolution strategy, using a smaller low-Fnum domain for near-field plume accuracy and a larger high-Fnum domain for wave-propagation coverage, is applied at 160 km, and the high-Fnum configuration is then applied at 180 km, along the Falcon 9 FT Iridium NEXT-4 second-stage trajectory. The resulting simulation matrix is presented, with 2D and 3D results for the 160 km case and 3D results for the 180 km case, demonstrating acousticdominated wave generation and pronounced upper/lower asymmetry due to atmospheric stratification. The framework provides a computational approach for investigating plume-generated disturbances and their propagation through the high-altitude atmosphere.