Fluid near tube wall is faster than free stream

cpadam · January 31, 2014, 10:24

I'm getting odd results and need some help. I have a slug of liquid initially resting in a pipe, then at t=0 I start pushing it through the pipe with a pressurized gas at a high temperature (2000K). I'm doing a transient, 2D, axisymmetric simulation using the VOF model and realizeable k-epsilon for turbulence. I also have the energy equation enabled.

My problem is that the liquid near the wall (but not at the wall) accelerates faster than the fluid in the center of the pipe. This is counterintuitive; I would expect the fluid at the center to accelerate the fastest. I don't know if this is a purely numerical artifact (maybe mesh is too coarse or time step too large?), or if there's some setting I missed. If anyone has any experience with this behavior I would greatly appreciate any advice. I can also send a screen shot if you want to see what's going on.

chandu · February 4, 2014, 11:11

did u create and fluid zone in center.

chandu · February 4, 2014, 11:12

did u create any fluid zone in center.

cpadam · February 4, 2014, 14:28

I did specify a fluid zone where there should be fluid. I think the problem may be in my choice of turbulence model. I have very high Reynolds numbers and I was using the standard k-e model. I'm trying some different things to see what makes a difference. Thanks for your help.

January 31, 2014, 10:24	Fluid near tube wall is faster than free stream	#1
cpadam New Member Join Date: Feb 2013 Posts: 11 Rep Power: 13	I'm getting odd results and need some help. I have a slug of liquid initially resting in a pipe, then at t=0 I start pushing it through the pipe with a pressurized gas at a high temperature (2000K). I'm doing a transient, 2D, axisymmetric simulation using the VOF model and realizeable k-epsilon for turbulence. I also have the energy equation enabled. My problem is that the liquid near the wall (but not at the wall) accelerates faster than the fluid in the center of the pipe. This is counterintuitive; I would expect the fluid at the center to accelerate the fastest. I don't know if this is a purely numerical artifact (maybe mesh is too coarse or time step too large?), or if there's some setting I missed. If anyone has any experience with this behavior I would greatly appreciate any advice. I can also send a screen shot if you want to see what's going on.

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February 4, 2014, 11:11		#2
chandu New Member chandramouli Join Date: Jan 2014 Posts: 4 Rep Power: 12	did u create and fluid zone in center.

February 4, 2014, 11:12		#3
chandu New Member chandramouli Join Date: Jan 2014 Posts: 4 Rep Power: 12	did u create any fluid zone in center.

February 4, 2014, 14:28		#4
cpadam New Member Join Date: Feb 2013 Posts: 11 Rep Power: 13	I did specify a fluid zone where there should be fluid. I think the problem may be in my choice of turbulence model. I have very high Reynolds numbers and I was using the standard k-e model. I'm trying some different things to see what makes a difference. Thanks for your help.