Hello Timm!

It would be nice if you may have a look on my calculations, due to the accuracy!

I want to simulate an 3D flow around a cylinder.

I try to calculate some unit conversations with different tau and different resolutions. Because with same taus and increasing resolutions, ulb going to be smaller. Im not that skilled with palabos to know what resolution i have to chose for correct solutions, but not to excessive computational costs.

May you can give me a tip!?

My physical essentials:

Re=500

velocity u=0,00502 m/s

kin.viscosity v=1,004e-6 m^2/s (water 20°C)

lenght of domain H=2,6m

cylinder diameter d=0,1m

From your linked ppt:

Re=(u*d)/v=Re_=500*

CRe=Re/Re_=1=(CuCh)/Cv

->Cu=Cv/Ch

with:

Ch=H/H_

(H_ resolution for domain lenght)

Cv= v/v_=v/vlb

(v_=vlb=(tau-1/2)/3 depending on chosen tau)

and finally to come to an ulb:

Cu=u/u_=u/ulb -> ulb=u/Cu

for tau = [0,51/ 0,515 / 0,52/ 0,55] and resolution H_=200 i calculated:

ulb=[0,216/ 0,325/ 0,433/ 1,008]

That seems way to large, so i increased H_ while leaving tau constant:

tau=0,51 H_=300 -> ulb=0,144

tau=0,51 H_=500 -> ulb=0,0867

tau=0,51 H_=600 -> ulb=0,072

tau=0,51 H_=800 -> ulb=0,0541

But the number of cells/nodes are drastically increased with larger H_.

So first: are the calculations correct?

and second: What constallation you would recommend? Or shall i go ahead with larger tau and larger resolution for a smaller ulb?

Thanks for your help!

georg