14 papers · 1 filter
Noise-separated evidence for a slow collective displacement in a rarefied hypersonic bow-shock layer
Ahmad Shoja-sani, Ehsan Roohi
Time-resolved direct simulation Monte Carlo (DSMC) fields are used to test whether a detached rarefied hypersonic bow shock contains a slow collective displacement that can be sepa…
Cross-stream pressure support and the limits of scalar relaxation in rarefied Poiseuille flow
Omid Ejtehadi, Ehsan Roohi
The weak wall-normal pressure variation in pressure-driven rarefied Poiseuille flow is a stringent test of higher-order constitutive models: it is almost invisible in the total-pre…
Gaussian kinetic representations of rarefied nonequilibrium flows
Ehsan Roohi
Compact representations of rarefied flows must preserve kinetic observables, not only smooth macroscopic fields. We introduce Gaussian kinetic representations for discrete velocity…
Quantity-Dependent Bulk-to-Wall Observability of Surface Loading in Rarefied Hypersonic Flow over Triangular Protrusions
Elyas Lekzian, Ehsan Roohi
Localized protrusions on hypersonic vehicles generate pressure, heat-transfer, and shear loads whose rarefied response can depend on gas beyond the immediate wall neighborhood. Thi…
Machine learning for rarefied gas transport in vacuum and micro/nano systems: promise, pitfalls, and a verification agenda
Ehsan Roohi
Machine learning is beginning to influence rarefied-gas modeling at multiple levels, including equation-solving, operator learning, learned collision physics, moment closures, dire…
Anti-Fourier heat flux does not certify the fourth-order closure state of a rarefied cavity
Ehsan Roohi
Cold-to-hot heat transfer in rarefied cavities is usually treated as a signature of Fourier-law failure. Here it is used to ask whether a correct anti-Fourier heat-flux field certi…