hi

i am a total newbie to lattice boltzmann

i am using d3q19 model to solve 3D pipe flow

i use bounce back condition at the boundaries

wrap around in flow direction

and forcing to impose direction of flow(add .001 to feq for the concerned direction)

in calculation of nu the eqn nu=(tao-.5)/3 is used and comes out to be .16666 for tao =1

i know the diameter of the pipe in lattice units depending on my initialisation of boundary

vavg is calculated from the result

i assumed speed of sound © to be 1

with this when i calculate re=vavg *d/nu
i generally get a 2 digit reynolds number
even if i take a large mesh of 50*50

*50*

i get a parabola which fits the analytical result of V/Vmax=(1-(r/R)^2) on making everything dimensionless

but i am starting to get deviations from my plot at a small re of around 35 which is for a mesh of 5151*51

i get a parabola which fits the analytical result of V/Vmax=(1-(r/R)^2) on making everything dimensionless

but i am starting to get deviations from my plot at a small re of around 35 which is for a mesh of 51

any and all help will be greatly appreciated

thanks in advance

pls help guys am really desperate