Oh I thought I was trying to do something stupidly simple to start with... grrrr

DDB · January 3, 2013, 05:29

ok, this is ridiculously stupid and I am unbelievably frustrated... I am a newbie to foam and I can't see me sticking around for long if this continues!

I have v2.1.1 installed, the official rpm for f17.

I have a channel, 15ftx7.5ftx3ft, a stupidly coarse grid for testing purposes of just over 21k cells. I have modified the file from the lid driven cavity to produce my channel in blockMesh.

I am using simpleFOAM.

I have done loads of tutorials, the problems arise when I try to do my own stuff

I want to have a velocity inlet and a pressure outlet. I want my velocity to be a positive (say 70m/s in x direction).

I have no patience with paraview, it seems totally unintuitive to me, so I am converting to fluent to check things as this works for me.

Why does my velocity inlet read into fluent as a pressure outlet?

Why does my pressure outlet velocity always end up equalling the exact negative of the velocity inlet when I have 'run' the simulation?

I can get things to work perfectly when I create the initial mesh in blockmesh, read into fluent, change the bits that are totally wrong, save as a case, convert back to foam and then run - but what good is that if I want to use free software?????

Please, someone, what is going on here?

DDB · January 3, 2013, 05:51

I should probably add that I am not new to CFD, just foam.

I am using the following BCs, as in tutorials and this post http://www.cfd-online.com/Forums/ope...flow-pipe.html

Inlet: U fixedValue, p zeroGradient
Outlet: U zeroGradient, p fixedValue uniform 0
Walls: U fixedValue uniform (0 0 0), p zeroGradient

mturcios777 · January 3, 2013, 12:12

The mapping between BCs going from OpenFOAM to Fluent and vice versa is not exact. If you are specifying your boundary conditions as mentioned in your last post, everything should work. Paraview is used mainly for pre-processing internal fields/boundary values and post-processing results; its not as useful for checking your boundary conditions.

Based on these boundary conditions, are you not getting the flow you expect? Could you throw your case up for us to see (only include blockMeshDict in the polyMesh directory)?

January 3, 2013, 05:29	Oh I thought I was trying to do something stupidly simple to start with... grrrr	#1
DDB New Member DDB Join Date: Jan 2013 Posts: 12 Rep Power: 13	ok, this is ridiculously stupid and I am unbelievably frustrated... I am a newbie to foam and I can't see me sticking around for long if this continues! I have v2.1.1 installed, the official rpm for f17. I have a channel, 15ftx7.5ftx3ft, a stupidly coarse grid for testing purposes of just over 21k cells. I have modified the file from the lid driven cavity to produce my channel in blockMesh. I am using simpleFOAM. I have done loads of tutorials, the problems arise when I try to do my own stuff I want to have a velocity inlet and a pressure outlet. I want my velocity to be a positive (say 70m/s in x direction). I have no patience with paraview, it seems totally unintuitive to me, so I am converting to fluent to check things as this works for me. Why does my velocity inlet read into fluent as a pressure outlet? Why does my pressure outlet velocity always end up equalling the exact negative of the velocity inlet when I have 'run' the simulation? I can get things to work perfectly when I create the initial mesh in blockmesh, read into fluent, change the bits that are totally wrong, save as a case, convert back to foam and then run - but what good is that if I want to use free software????? Please, someone, what is going on here?

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
TimeVaryingMappedFixedValue	irishdave	OpenFOAM Running, Solving & CFD	32	June 16, 2021 06:55
SIMPLE algorithm in 3D cylindrical coordinates	zouchu	Main CFD Forum	1	January 20, 2014 17:02
Problem in running ICEM grid in Openfoam	Tarak	OpenFOAM	6	September 9, 2011 17:51
Start star ccm+ remotely with mpiexec	Dagnir	Siemens	0	November 24, 2010 12:33
Lets start the public domain CFD-Project!	Heinz Wilkening	Main CFD Forum	3	March 11, 1999 22:55

January 3, 2013, 05:51		#2
DDB New Member DDB Join Date: Jan 2013 Posts: 12 Rep Power: 13	I should probably add that I am not new to CFD, just foam. I am using the following BCs, as in tutorials and this post http://www.cfd-online.com/Forums/ope...flow-pipe.html Inlet: U fixedValue, p zeroGradient Outlet: U zeroGradient, p fixedValue uniform 0 Walls: U fixedValue uniform (0 0 0), p zeroGradient

January 3, 2013, 12:12		#3
mturcios777 Senior Member Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 740 Rep Power: 28	The mapping between BCs going from OpenFOAM to Fluent and vice versa is not exact. If you are specifying your boundary conditions as mentioned in your last post, everything should work. Paraview is used mainly for pre-processing internal fields/boundary values and post-processing results; its not as useful for checking your boundary conditions. Based on these boundary conditions, are you not getting the flow you expect? Could you throw your case up for us to see (only include blockMeshDict in the polyMesh directory)?