Moving refine one line below stream cost a 7.2x error — the recursive time cycle of LBM AMR
·7 min read
Moving refine below stream on the same LBM grid raises the L2 error from 0.657% to 4.704%, a factor of 7.2, and the excess sits on the seam.
ρ and u Agree to the Last Digit While the Strain Rate Swells 45% — Nonequilibrium Rescaling at an LBM Refinement Interface
·8 min read
Copying distribution functions across an LBM AMR level interface keeps ρ and u exact but inflates the stress by up to 2x. I measured the rescale factor.
Same Answer From 18% of the Cells — AMR Tagging Criteria and Coarse-Fine Refluxing
·9 min read
Wrapping a 256^2 shear layer in 3-level AMR leaves 11,776 cells, 18% of 65,536. Reflux off drifts mass by about 1% in 60 steps.
Quadtree AMR — Letting the Mesh Grow Where It Needs To
·7 min read
Level-7 uniform needs 128 cells; one Gaussian keeps 41 leaves, about 32 percent. A quadtree, slope threshold tau, and a 2:1 rule decide which cells split.