ρ and u Agree to the Last Digit While the Strain Rate Swells 45% — Nonequilibrium Rescaling at an LBM Refinement Interface
·7 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.
A 1% Error in Diameter Is a 4% Error in Flow Rate — Half a Cell of Wall and Poiseuille's Constant
·7 min read
Pipe flow rate rides on the fourth power of the diameter. The same exponent explains a mesh with the wall half a cell off and Poiseuille's 1838 glass tubes.
I Dropped the −1/2 and the Viscosity Came Back Six Times Too Large — the Δt/2 Left Behind by LBM's Discretisation
·6 min read
One trapezoidal integration and one change of variables leave a Δt/2 in three separate places: the viscosity, the velocity, and the stress. A scalar ODE and a D2Q9 lattice measure all three.
Viscosity Is Not What Kills a Vortex — Newton's 1/r and the Lamb–Oseen Core
·7 min read
A free vortex carries huge shear stress and still refuses to decay. The core and the wall hold the clock.
The Paramecium Swims Through Honey — Where Viscosity Comes From and Why Fourier and Fick Wrote the Same Line
·5 min read
Molecules carry momentum across an imaginary plane — and one identity ties viscosity, heat, and diffusion together