Pushing the Frame to 0.2 Cut the Viscosity by 5.97% — The Missing Third Moment in LBM Equilibria
On D2Q9, Σf c³ equals ρu for any distribution you can write. The missing ρu³ breaks Galilean invariance and makes measured viscosity depend on the frame.
27 of 1,681 Voxels Flipped Inside Out — Ray Parity and Link Cutting in STL Voxelization
Turning an STL into an LBM voxel grid takes four stages: octree culling, SAT overlap tests, ray parity, and the per-link cut fraction q, verified in code.
Doubling τ Left Pr at 1.0000 — The Two Constants Locked Inside Thermal LBM
A single-distribution thermal LBM ties viscosity and thermal diffusivity to one τ, locking Pr at 1. I measured on D2Q9 what a second distribution unlocks.
ρ and u Agree to the Last Digit While the Strain Rate Swells 45% — Nonequilibrium Rescaling at an LBM Refinement Interface
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.
I Dropped the −1/2 and the Viscosity Came Back Six Times Too Large — the Δt/2 Left Behind by LBM's Discretisation
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.
Three at a wall, five at a corner — counting the populations an LBM boundary node loses
After streaming, the number of empty populations at a lattice-Boltzmann node equals the number of solid cells around it: three on a flat wall, five in a concave corner, one on a convex corner.
I Plugged in Pressure Directly and a Still Interface Started to Shiver — Two Forms of Nonideal LBM Forcing
When a van der Waals fluid is solved with lattice Boltzmann, putting pressure p in the force term versus chemical potential mu agrees in the continuum but splits on the lattice.
Raise the Velocity, Lose 27% of Your Diffusion — The Extra Flux in LBM Convection-Diffusion
Set D through tau in a lattice Boltzmann convection-diffusion model and it still spreads at D(1-u²/cs²). Where Chapman-Enskog drops the extra flux, and the source term that erases it.
Where Half the Force Goes in LBM — Four Forcing Schemes and 1−1/(2τ)
Comparing lattice Boltzmann body-force schemes and pinning down the half-force correction
In Lattice Boltzmann, the Wall Isn't on the Node — Bounce-Back and Zou-He Boundaries
The bounce rule that builds a no-slip wall, and where that wall really sits
Surviving the Low-Viscosity Regime Where BGK Blows Up — MRT Lattice Boltzmann Collision
Pushing past single-relaxation-time BGK with moment-space multiple relaxation in MRT-LBM
Entropy Stops the Blow-Up — Karlin's Entropic Lattice Boltzmann
Stabilizing LBM with an H-theorem-enforcing entropic collision
Nine Arrows of Maxwell–Boltzmann — Why LBM's Equilibrium Is a Polynomial
A second-order Hermite truncation builds D2Q9, and the same truncation chains LBM to low-Mach flows