# BuoyantFoam problem

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 November 7, 2008, 10:24 Just a precision: imposing no #21 Member   Pattyn Eric Join Date: Mar 2009 Posts: 61 Rep Power: 8 Just a precision: imposing no boundary condition for temperature at the Outlet would mean for me to use a "calculated" condition. When trying to use it, i receive the following error: Starting time loop Courant Number mean: 0.00606061 max: 0.133333 Time = 0.0005 diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0 DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 1.13964e-06, No Iterations 3 DILUPBiCG: Solving for Uz, Initial residual = 0.999969, Final residual = 2.03988e-07, No Iterations 4 gradientInternalCoeffs cannot be called for a calculatedFvPatchField on patch Outlet of field h in file "/net/ric_home/ep4/OpenFOAM/eric-1.5/run/Flatplate_no_buoyant_unstaedy/0/h" You are probably trying to solve for a field with a default boundary condition. From function calculatedFvPatchField::gradientInternalCoef fs() const in file fields/fvPatchFields/basic/calculated/calculatedFvPatchField.C at line 187. FOAM exiting

 November 7, 2008, 11:13 Hello Eric, Quoting from y #22 Member   Prashant Ojha Join Date: Mar 2009 Posts: 38 Rep Power: 8 Hello Eric, Quoting from your post: "It appears me logical tu use a fixed temperature at the inlet and the plate, a zeroGradient condition at the boundary Up (infront of the plate)." Thats right, I take back my words. I misread your earlier post and had a completely different case in my mind while replying. Well, I am retiring for the day but I would like you to check the following boundary conditions. p: internalField uniform 100000; boundaryField { WallDown { type calculated; value uniform 100000; } Inlet { type zeroGradient } Outlet { type zeroGradient; } Up { type zeroGradient; } } // ************************************************** *********************** // pd: dimensions [1 -1 -2 0 0 0 0]; internalField uniform 0; boundaryField { WallDown { type fixedFluxBuoyantPressure; value uniform 0; } Inlet { type fixedValue; value uniform 50; } Outlet { type fixedValue; value uniform 0; } Up { type fixedValue; value uniform 0; } frontAndBack { type empty; } } // ************************************************** *********************** // T: dimensions [0 0 0 1 0 0 0]; internalField uniform 300; boundaryField { WallDown { type fixedValue; value uniform 300; } Inlet { type fixedValue; value uniform 300; } Outlet { type zeroGradient; } Up { type zeroGradient; } frontAndBack { type empty; } } // ************************************************** *********************** // U: dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { WallDown { type fixedValue; value uniform (0 0 0); } Inlet { type fixedValue; value uniform (10 0 0); } Outlet { type zeroGradient; } Up { type zeroGradient; } frontAndBack { type empty; } } // ************************************************** *********************** //

 November 7, 2008, 11:33 You were right, setting turbul #23 Member   Pattyn Eric Join Date: Mar 2009 Posts: 61 Rep Power: 8 You were right, setting turbulence off and the simulation is ok. However, i don't know what i should do in order to use the kEpsilon model. Change my initial values for k and epsilon? I had followed the example in tutorial (User guide U-41). Is it possible that the initial values of epsilon and k influences my results (it can diverge!) even if i have set teubulence off?? Thanks Eric

 November 8, 2008, 01:39 It seems that the discretizati #24 Member   Prashant Ojha Join Date: Mar 2009 Posts: 38 Rep Power: 8 It seems that the discretization needs tuning, if you keep on getting the bounding error for k and epsilon the solution may blow up. Just try tightening your tolerances. Regards,

 November 13, 2008, 14:34 Hello Foamers, i also have #25 New Member   Oliver Sommer Join Date: Mar 2009 Posts: 12 Rep Power: 8 Hello Foamers, i also have a problem with the buoyantFoam solver. I want to simulate a Cell with 1.1mmx10mm in x-y direction and 2D. For testing i let the Fluid "air" in the "thermophysicalProperties"-File (simply copied the hotRoom example), but now i want to change to a liquid. Do i have to change the "thermoType"? Because i read in the Openfoam website something about liquids and so on. And in which combination can i use the keywords out from the UserGuide? test case with "air": hThermo>>>> The problem is, when i change the vaules for W, c_p, eta and Pr to the liquids (n_moles [1] and H_f [o] not changed) the velocities don't fit the experiment results. But is is of course different to the "air"-result. Do i have to set the H_f value? Do i need it only when i want to "melt ice to water"? thank you in advance greets

 November 14, 2008, 06:52 Hi, I'm considering a heate #26 Member   Pattyn Eric Join Date: Mar 2009 Posts: 61 Rep Power: 8 Hi, I'm considering a heated channel flow. On the plate, where the velocity is zero, the value of pd is different of zero while i thought pd was the dynamic pressure... Actually, i have a variation along x (direction of the flow) which makes me think to a rho g h quantity but i have set g=0 in the environnemental properties. I have the similar problem with the p quantity of turbFoam, which is the kinematic pressure (User guide U-22). If p= rho V^2/2, for the same case but without heat, p should be 0 on the wall. However, i have the same value as pd for the heated case. Could someone help me to understand what are these variables exactly? Thank you Eric

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