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October 7, 2018, 16:06 |
rhoInf value, postProcess
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#1 |
New Member
Join Date: Jul 2018
Posts: 9
Rep Power: 8 |
Hello FOAMers,
I'm new in OF and I'm a little confused about the value of "rhoInf". I'm using the interDyMFoam solver (which means that my fluids are incompressible) and I want to calculate the forces and the moments on a patch of my simulation model. In the "system" file I've already copied the "forcesIncompressible" file. Now, in order to run Code:
interDyMFOAM -postProcess -func forcesIncompressible Code:
phases (water air); water // oil ISOVG150 { transportModel Newtonian; nu nu [0 2 -1 0 0 0 0] 2.280290891e-05; rho rho [1 -3 0 0 0 0 0] 811.3; } air { transportModel Newtonian; nu nu [0 2 -1 0 0 0 0] 213.5e-07 ; rho rho [1 -3 0 0 0 0 0] 0.9859; } sigma sigma [1 0 -2 0 0 0 0] 0.02843192; Is there someone who could help me? |
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October 8, 2018, 11:29 |
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#2 | ||
Super Moderator
Tobias Holzmann
Join Date: Oct 2010
Location: Bad Wörishofen
Posts: 2,711
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Hi, as far as I know, the force calculation can only be used for single phase flows. You should be able to use the functionality for your case too but I am not sure if the result will be fine (if the object is in both fluids, I would expect that the result is wrong). However, the keyword rhoInf is used for incompressible calculations because the functionObject does not know the density. Thus, the keyword has to be used to tell the application which value has to be used for the calculation, cf. https://cpp.openfoam.org/v6/forces_8C_source.html
Code:
if (directForceDensity_) { // Optional entry for fDName fDName_ = dict.lookupOrDefault<word>("fD", "fD"); } else { // Optional entries U and p pName_ = dict.lookupOrDefault<word>("p", "p"); UName_ = dict.lookupOrDefault<word>("U", "U"); rhoName_ = dict.lookupOrDefault<word>("rho", "rho"); // Reference density needed for incompressible calculations if (rhoName_ == "rhoInf") { dict.lookup("rhoInf") >> rhoRef_; } // Reference pressure, 0 by default pRef_ = dict.lookupOrDefault<scalar>("pRef", 0.0); } Quote:
Quote:
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Keep foaming, Tobias Holzmann |
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November 1, 2018, 02:12 |
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#3 | |
Member
Dongxu Wang
Join Date: Sep 2018
Location: China
Posts: 33
Rep Power: 8 |
Quote:
I have a similar problem. I also used interDyMFoam to simulate the wave-sturcture interaction. I wanted to calculate the total force of the structure in my numerical wave tank and I adopted this force functions in my controlDict: forceOFcaisson { type forces; libs ("libforces.so"); writeControl timeStep; writeInterval 1; rho rhoInf; // Incompressible solver rhoInf 1000; log off; patches (caisson); CofR (0 0 0); } The structure (patch) is fixed and named with "caisson", and the simulation is three-demensional so the structure is a little complicated. The pressure obtained by function "Probes" agrees good with that obtained by sensors in the experiment. The shape of the two curves of the total force (vertical and horizontal) seems good. However, the value seems not right. We believe that the kinematic pressure is greater than it should be. My question is: Is there a way to obtain the total force of a complicated structure (patch) when using interFoam? Thank you very much! D.X. Wang |
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