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-   -   Study about a radiator (http://www.cfd-online.com/Forums/openfoam-solving/102191-study-about-radiator.html)

vinezio May 24, 2012 11:51

Study about a radiator
 
3 Attachment(s)
Hi Foamers,
i'm working to study the behaviour of a radiator which it has 3 simple fingers. I use simpleFoam solver with realizableKE method for Newtonian fluid (water). I set up BCs in this way:

INLET
p --> zeroGradient
U --> flowRateInletVelocity
k --> initial value
epsilon --> initial value
nut --> calculated

WALL
p --> zeroGradient
U --> fixedValue 0
k --> kqRWallFunction
epsilon -->epsilonWallFunction
nut --> 0 value

OUTLET
p --> 0 value
U --> ?
k --> ?
epsilon --> ?
nut --> calculated
[Really, i've tried several method for the outlet, but i'm not sure about the right way ( inletOutlet, outletInlet, zeroGradient)].

Main goal is to find the velocity field and to reach the convergence in better way possible (time convergence, velocity's iteration, accuracy of solution).

For now, nothing!! I don't know if i forget somethink or what. Why, when i've visualized in the paraview, does solution change for first time step, while not change for all rest (to each case that i tried)?

I post my fingers and fvSolution, fvSchemes files.

Regards!!! Vincenzo

vinezio May 24, 2012 18:02

I would clarify one thing.. my first object is to understand which and why outlet's BCs must be used and the effects for each choosing. How I may set fvSchemes to have a corrected and consistent solution (for now, every solution is not correct).

After, i would discuss how the solution can be developed and improved.

Thanks to all!!

vinezio May 26, 2012 08:04

Hi all,
i'm trying to solve first problem of my case and i'm using inletOutlet for outlet's BCs in way to have zeroGradient. When simulation starts k converges rapidly and the other functions stay blocked. is It normal?? why don't the solution changes step by step?

i show what happened:

Time = 170

smoothSolver: Solving for Ux, Initial residual = 0.00055745698614, Final residual = 3.33918560038e-05, No Iterations 3
smoothSolver: Solving for Uy, Initial residual = 0.000123258066429, Final residual = 5.73185318398e-06, No Iterations 3
smoothSolver: Solving for Uz, Initial residual = 0.0023174939628, Final residual = 0.000141865924374, No Iterations 3
GAMG: Solving for p, Initial residual = 0.0162594175753, Final residual = 0.000702701530115, No Iterations 2
GAMG: Solving for p, Initial residual = 0.00418840145534, Final residual = 0.000153441787867, No Iterations 2
GAMG: Solving for p, Initial residual = 0.000983064579696, Final residual = 3.89487037296e-05, No Iterations 2
time step continuity errors : sum local = 0.00223007456523, global = -1.9700845204e-06, cumulative = 0.114629259665
smoothSolver: Solving for epsilon, Initial residual = 1.65537958175e-05, Final residual = 4.27652710707e-07, No Iterations 2
smoothSolver: Solving for k, Initial residual = 3.0933136533e-15, Final residual = 1.16840246856e-18, No Iterations 1
bounding k, min: 1.63989417126e-16 max: 3.65473424164 average: 0.0675839376248
ExecutionTime = 208.77 s ClockTime = 210 s

........
step by step
........

Time = 12000

smoothSolver: Solving for Ux, Initial residual = 0.000549283976902, Final residual = 3.23141590569e-05, No Iterations 3
smoothSolver: Solving for Uy, Initial residual = 0.000122228232637, Final residual = 5.56535850175e-06, No Iterations 3
smoothSolver: Solving for Uz, Initial residual = 0.0023001188588, Final residual = 0.000139948342846, No Iterations 3
GAMG: Solving for p, Initial residual = 0.0162353270075, Final residual = 0.000701558822586, No Iterations 2
GAMG: Solving for p, Initial residual = 0.00418917486882, Final residual = 0.000153149749499, No Iterations 2
GAMG: Solving for p, Initial residual = 0.000984176710849, Final residual = 3.88102094469e-05, No Iterations 2
time step continuity errors : sum local = 0.00222174367168, global = -3.00503702014e-06, cumulative = 0.113463870741
smoothSolver: Solving for epsilon, Initial residual = 1.61319652077e-05, Final residual = 4.02583277545e-07, No Iterations 2
smoothSolver: Solving for k, Initial residual = 3.0683752838e-15, Final residual = 1.04489246622e-18, No Iterations 1
bounding k, min: -8.45616718634e-10 max: 3.65502015206 average: 0.067576246466
ExecutionTime = 13908.82 s ClockTime = 13927 s

Thanks to all!!


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