A Wall the Grid Never Sees — IBM Delta Kernels and Multi-Direct Forcing
·9 min read
One forcing pass leaves 64% of free-stream slip on a cylinder. At Δs/h = 3 the gap slip hits 0.287, and at 0.25 the condition number reaches 1e11.
A Heart Valve Without a Body-Fitted Mesh — Peskin's Immersed Boundary Method and the Discrete Delta
·6 min read
Peskin's four-point delta sums to one on the grid. The listing's 24 markers on a radius-8 cylinder sit more than two cells apart, so the wall stays gappy.