Hi every body
consider a flow in channel. channel width is H. boundary condition is inlet pressure=Pi and outlet pressure Po.
Note that reynolds is unknown because we dont have any charactristic velocity.
if we consider charactristic length= H then delta_x=1/N(number of nodes). but my question is that How can I found delta_t to transfer unit from lattice to physical unit and vice versa???:((
If one BC was velocity it can be solved easily. For example if inlet=Ui we have:
taking U_charactristic-in-lattice=0.1 and U_charactristic= Ui ::::>> delta_t=U_charactristic-in-latticedelta_x
=========>>>> U=U_charactristicU_lattice(that we obtain it from solveing LBM)delta_x/delta_t=Ui0.1*delta_x/delta_t
As you see when velocity is known the unit transfer is easy but when we have pressure in inlet and outlet how we can transfer units???:(((((
thanks for your answer

Dear brucedjones
thank you very very much
but there is some problem
consider I use your proposed equation. if I consider e.g tau=1 then dt can be found. but how I can transfer pressure in real to lattice. you know that pressure dimension is:
kg/(m s^2)
now what about kg???
I really am confused. I read the notes of latt:
Choice of units in lattice Boltzmann simulations
Jonas Latt
but my problems remain:((((
thanks a lot