Cannot validate simple pipe flow using simpleFoam

inf.vish · August 6, 2013, 05:08

Hi all,

I am new to OpenFOAM and I am required to validate the simple case of a flow through a pipe. The boundary conditions are
U - fixedvalue at inlet, zerogradient at outlet and fixedvalue zero at walls
p - zerogradient at inlet and wall, fixedvalue zero at outlet.

The solution shows two peaks in pressure at the inlet corners. I am using Poiseuille's law and the pressure difference i calculate is not even close to that is shown by openfoam.

I am attaching my case files here. 2D_pipe_vel_driven.zip

laurentb · August 6, 2013, 05:43

Hi,

For a 2d axisymmetric case you should use the WEDGE type for your mesh.
Have a look to : http://www.somogyibence.hu/documents.../Cornell1.html

inf.vish · August 6, 2013, 06:21

Why can't i just normally solve it?

inf.vish · August 6, 2013, 06:33

The results match now. Can you explain me why the normal approach doesn't work and the wedge approach works?

inf.vish · August 6, 2013, 07:32

Okay, so i understand why the problem was there. Wedge is a part of a circle and a 2D rectangle (which openfoam converts to 3D block) would represent a pipe with rectangular cross section.

There is however one more problem. I should get correct results if i make a 3D pipe of circular cross section and run the simulation. My results are not conforming with Poiseuille's Law.

The mesh file is too big to upload over here. It was meshed on Fluent. 10mm dia and 100mm length.

August 6, 2013, 05:08	Cannot validate simple pipe flow using simpleFoam	#1
inf.vish Member Vishal Join Date: Jul 2013 Posts: 73 Rep Power: 12	Hi all, I am new to OpenFOAM and I am required to validate the simple case of a flow through a pipe. The boundary conditions are U - fixedvalue at inlet, zerogradient at outlet and fixedvalue zero at walls p - zerogradient at inlet and wall, fixedvalue zero at outlet. The solution shows two peaks in pressure at the inlet corners. I am using Poiseuille's law and the pressure difference i calculate is not even close to that is shown by openfoam. I am attaching my case files here. 2D_pipe_vel_driven.zip

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August 6, 2013, 05:43		#2
laurentb Member Laurent B Join Date: Jun 2009 Location: Lille, FRANCE Posts: 70 Rep Power: 16	Hi, For a 2d axisymmetric case you should use the WEDGE type for your mesh. Have a look to : http://www.somogyibence.hu/documents.../Cornell1.html

August 6, 2013, 06:21		#3
inf.vish Member Vishal Join Date: Jul 2013 Posts: 73 Rep Power: 12	Why can't i just normally solve it?

August 6, 2013, 06:33		#4
inf.vish Member Vishal Join Date: Jul 2013 Posts: 73 Rep Power: 12	The results match now. Can you explain me why the normal approach doesn't work and the wedge approach works?

August 6, 2013, 07:32		#5
inf.vish Member Vishal Join Date: Jul 2013 Posts: 73 Rep Power: 12	Okay, so i understand why the problem was there. Wedge is a part of a circle and a 2D rectangle (which openfoam converts to 3D block) would represent a pipe with rectangular cross section. There is however one more problem. I should get correct results if i make a 3D pipe of circular cross section and run the simulation. My results are not conforming with Poiseuille's Law. The mesh file is too big to upload over here. It was meshed on Fluent. 10mm dia and 100mm length.