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Computational Modeling of Meteor-Generated Ground Pressure Signatures

AMS Seminar Series

Speaker: Marian Nemec, Computational Aerosciences Branch, NASA Ames Research Center

Presentation

Seminar Slide Deck (PDF-22MB)

Abstract

We present a thorough validation of a computational approach to predict infrasonic signatures of centimeter-sized meteoroids. This is the first direct comparison of computational results with well-calibrated observations that include trajectories, optical masses and ground pressure signatures. We assume that the energy deposition along the meteor trail is dominated by atmospheric drag and simulate a steady, inviscid flow of air in thermochemical equilibrium to compute a near-body pressure signature of the meteoroid. This signature is then propagated through a stratified and windy atmosphere to the ground using a methodology adapted from aircraft sonic-boom analysis. In particular, we use Cart3D in conjunction with sBOOM.

The freestream Mach numbers of the selected meteor events are between 40 and 100, and the signatures are propagated from heights of 50—70 km. The results show that when the source of the signature is the cylindrical Mach-cone, the simulations closely match the observations. The prediction of the shock rise-time, the zero-peak amplitude of the waveform and the duration of the positive pressure phase are consistently within 10\% of the measurements. Uncertainty in primarily the shape of the meteoroid results in a poorer prediction of the trailing part of the waveform. Overall, our results independently verify energy deposition estimates deduced from optical observations.

Biography

Marian Nemec is an Aerospace Engineer in the Computational Aerosciences Branch of the Advanced Supercomputing Division at NASA Ames. He has 15 years of experience in the development of adjoint methods for discretization error analysis and shape optimization, embedded-boundary Cartesian mesh methods, adaptive mesh refinement and the application of these methods to complex geometry problems. He was awarded the NASA Exceptional Public Achievement Medal in 2012 for his contributions to computational aerodynamics and the ARMD AA Award for the development of the Cart3D shape-optimization framework. He obtained his PhD in 2003 from the University of Toronto Institute for Aerospace Studies, where his research involved developing an adjoint solver for the infamous ARC2D code, and he came to NASA Ames as a Post Doctoral Research Associate the same year.