One node pushed the error from 0.21% to 76% — local relaxation time in power-law LBM
·8 min read
One centreline node asks for infinite tau at n=0.6. Cap it near 4 and L2 error stays near 0.21%; leave it and that node drives the error to 76%.
2.0000 in laminar flow, 1.0322 in turbulent — the coefficient in front of the velocity head
·7 min read
A mean-velocity head is not the kinetic energy a pipe actually carries. Alpha is 2.0000 for laminar Poiseuille flow and 1.0322 at Re = 10^6.
Where Half the Force Goes in LBM — Four Forcing Schemes and 1−1/(2τ)
·10 min read
Steady Poiseuille gives the same error for five LBM forcing schemes. At τ=0.6, the half-shift alone inflates the amplitude by a factor of 1.83.
Poiseuille Flow: Analytical Solution Derivation and Finite Difference Validation
·5 min read
At h = G = μ = 1 the centerline speed is 1/2 and the flow rate is 2/3. FD L2 starts at 2.78e-16 and never leaves roundoff, so ~2.0 is not a measured order.