roughness in shallowWaterFoam

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 November 9, 2011, 04:46 roughness in shallowWaterFoam #1 New Member   Wolfgang Schanderl Join Date: Nov 2011 Location: Munich Posts: 2 Rep Power: 0 Hallo everybody, I want to do an open-channel simulation with shallowWaterFoam. How can I define the bed-roughness? Or do I have to model it somehow? Regards, Wolfgang

 July 16, 2013, 21:51 Are you looking to model a free-surface flow? #2 New Member   David Jessop Join Date: Jul 2013 Posts: 5 Rep Power: 12 Hi, This reply may come far too late for the original post but I hope it may help other openfoam users. I've been trying to model certain classes of free-surface gravity currents for which the horizontal length scale (x and/or y) is much larger than the vertical scale (z). In this framework, vertical accelerations are small compared to gravity, and the conservation equations can be depth averaged which leads to what are often called the shallow water equations. For this reason, I started to investigate the shallowWaterFoam solver. However, as is described in HTML Code: `http://www.tfd.chalmers.se/~hani/kurser/OS_CFD_2010/johanPilqvist/johanPilqvistReport.pdf` this solver has been written for atmospheric/oceanic flows where the depth (z) is large compared to the Earth's radius. Furthermore, the top and bottom stresses are assumed to be zero. Hence, as is, this solver cannot be used to treat the kind of problem that I've described above. However, with modifications to the equation set in shallowWaterFoam.C, the same files can be used to tackle these classes of problems via a finite volume method.

 July 22, 2013, 14:10 #3 Member   Haomin Yuan Join Date: Jan 2012 Location: Madison, Wisconsin, USA Posts: 59 Rep Power: 14 I think you can just use a rough wall function. You may look it up in turbulence model wall function source file.

 July 22, 2013, 14:31 #4 New Member   David Jessop Join Date: Jul 2013 Posts: 5 Rep Power: 12 That would mean that the "rough wall" would be one of the "frontAndBack faces". I don't think that would work as the domain is only one-cell thick in the depthwise direction, but I could be wrong.

 September 2, 2013, 03:58 #5 Senior Member   Join Date: Jul 2011 Posts: 120 Rep Power: 14 you are right. it would not work since it is only one cell thick. In depth averaged models the wind and bed stresses act as souce and sink to the momentum equations. I am currently working on this. cfdopenfoam likes this.

 September 4, 2013, 09:03 #6 Member   Andreas Ruopp Join Date: Aug 2009 Location: Stuttgart / Germany Posts: 31 Rep Power: 16 hi, for bottom roughness you just have to impose an additional source. I did that already and that works brilliantly. It is easy: Code: `...=lambda*hU` Best, andy

September 24, 2013, 02:49
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Quote:
 Originally Posted by andyru hi, for bottom roughness you just have to impose an additional source. I did that already and that works brilliantly. It is easy: Code: `...=lambda*hU` Best, andy
Hi Andy, did you include this in the hUEqn, momentumPredictor or inside the piso loop?

 September 24, 2013, 04:33 #8 Member   Andreas Ruopp Join Date: Aug 2009 Location: Stuttgart / Germany Posts: 31 Rep Power: 16 According to Jasak PhD http://powerlab.fsb.hr/ped/kturbo/Op...jeJasakPhD.pdf I added it to momentum predictor as well as in piso-loop.

September 24, 2013, 05:09
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Quote:
 Originally Posted by andyru According to Jasak PhD http://powerlab.fsb.hr/ped/kturbo/Op...jeJasakPhD.pdf I added it to momentum predictor as well as in piso-loop.
Can you show me how it can be implemented in both momentum predictor and pisoloop? I have a couple of term that I need to add in shallowWaterFoam.

Last edited by haze_1986; October 3, 2013 at 04:42.

 October 1, 2013, 01:34 #10 Senior Member   Join Date: Jul 2011 Posts: 120 Rep Power: 14 Fixed, thanks Last edited by haze_1986; October 3, 2013 at 04:43.

 August 28, 2023, 05:23 the roughness #11 New Member   Join Date: Aug 2023 Posts: 8 Rep Power: 2 Hi everyone, I am trying to simulate a river with openfoam, using the shallowWaterFoam solver. Is the solver still not considering bottom roughness? How may I add the manning roughness number in the simulation then? Thanks a lot in advance.

 Tags open channel flow, roughness, shallow water