2026/07/13 by Bjørn Wu · 1 citation
#math.NA #cs.NA #physics.flu-dyn
We propose a log-Gaussian scale-space limiter for hybrid continuum--ballistic gas dynamics. The method defines complementary continuum and ballistic weights as Gaussian cumulative probabilities in logarithmic Knudsen-number space, yielding a smooth transition between Navier--Stokes--Fourier and kinetic/free-molecular fluxes while suppressing asymptotically invalid correction branches in the continuum and free-molecular limits. The limiter is incorporated into a conservative finite-volume interface flux by blending a Navier--Stokes--Fourier flux with a half-range Maxwellian kinetic flux. Numerical tests using one-dimensional DVM/BGK Fourier and Couette benchmarks show that rarefaction corrections improve macroscopic profiles relative to NSF. A DVM/BGK-calibrated pair, K0=0.03 and sigma=2.5, reduces the combined mean profile error by about 40 percent for the tested planar wall-bounded flows. Additional diagnostics examine the BGK relaxation coefficient, heat-flux and shear-stress moment errors, parameter robustness, reduced DVM/BGK normal-shock activation, and two-dimensional blunt-body shock-layer activation. The method is intended as a lightweight proof-of-concept closure and diagnostic framework rather than a replacement for full kinetic solvers.