# Boundary Conditions for Spraysimulation

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 April 21, 2009, 05:20 Boundary Conditions for Spraysimulation #1 Member   Michael Join Date: Mar 2009 Posts: 48 Rep Power: 8 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

 April 22, 2009, 08:25 #2 Member   Michael Join Date: Mar 2009 Posts: 48 Rep Power: 8 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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