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-   -   Boundary Conditions for Spraysimulation (http://www.cfd-online.com/Forums/openfoam-solving/63825-boundary-conditions-spraysimulation.html)

farbfilm April 21, 2009 05:20

Boundary Conditions for Spraysimulation
 
Hi everybody,

I want to simulate a spray that impinge in a free atmosphere (under standard conditions) using dieselFoam! What are the right boundary conditions for that???

I made a simulation with the zeroGradient-condition for all boundaries! But here the calculation stagnates after a certain time! My assumption is, that there is something wrong with the pressure!

The following lines show an extract of the log-file shortly before the caclulation stagnate:
DICPCG: Solving for p, Initial residual = 0.377132, Final residual = 8.36049e-10, No Iterations 43
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.15917e-14, global = -5.01047e-16, cumulative = -2.09692e-12
DICPCG: Solving for p, Initial residual = 0.000416067, Final residual = 6.60735e-10, No Iterations 25
diagonal: Solving for rho, Initial residual = 0, Final residual = 0, No Iterations 0
time step continuity errors : sum local = 1.008e-14, global = -7.18694e-16, cumulative = -2.09764e-12

Can somebody help me????

Thanks, Michael

farbfilm April 22, 2009 08:25

Hi,

I'm still dealing with my problem...

In the meantime I saw in the 'dambreak'-tutorial that there is a boundary for an atmosphere! There the boundary conditions are:

U (velocity)

type pressureInletOutletVelocity;
value uniform (0 0 0);

p (pressure)

type totalPressure;
U U; \\ name of the velocity field
phi phi; \\ name of the volumetric flux field (or for the use of the muss flux field it will be devided by rho)
rho none; \\ name of the density field
psi none; \\ name of the derivative of density with respect to pressure
gamma 1.4; \\ ratio of specific heats
p0 uniform 1e+5; \\ value for totalPressure

(I wrote the explanations behind the quantities just for those people who have the same problem like me: to find out what are the quantities stand for...)

Now, my first questions: Is that kind of boundary condition even suitable for my spraysimulations?? Is it the right choice??

If yes, I guess in the totalPressure-boundary, U and phi have to be "turned on"!
But what about rho and phi (since dieselFoam is a compressible solver one of them should also be "turned on", right?). How do I have to handle these two quantities??

Can somebody please help me???

Thanks, Michael


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