I have been simulating pipe flow with velocity inlet and pressure outlet system. I am using LBM. for some reason the pressure at the inlet (if we go from 1 to 2000 in length pressure at lattice 10) is varying from one iteration to another for shear thickening fluid with power law index greater than 1.3. what could be possible problem which I can fix to get a constant pressure at the inlet in radial direction.
Usually pressure is constant across boundary-layer, here in radial direction. And in flow direction you should keep pumping energy upstream to compensate for energy loss due to friction so that you get constant pressure in streamline direction.
Please in last sentence above make a correction streamwise direction.
Hi Garima and all.
It looks as if you are simulating flow transients in pipelines. Question 1: does the same thing happen for a newtonian fluid? Mind you, it may happen for a very short time interval. Thus, if you’re using long time intervals on the simulation, the effect for a newtonian fluid could become imperceptible. Question 2: do you start simulation with an empty lattice or with a flooded lattice?
@R.P. Peçanha no it didn't happen for newtonian fluid.
And simulation is starting with flooded lattice
Hi Garima and all.
I wonder whether the shear thickening fluid used is too viscous so that simulations are subject to entrance and exit effects, where the flow is 2-D (cylindrical symmetry). That depends on the geometry involved (tank, pipeline etc.). This could lead to anusually long hydrodynamic entrance and exit lengths of pipe. Fluid velocity profiles are not fully developed in these regions and convective accelerations would have to be considered in simulations. If this is the case, you could try: (1) a less viscous shear thickening fluid; (2) increase the pipeline length, to lessen the relative contribution of entrance and exit effects to the total pressure drop; (3) combine (1) and (2) strategies.
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