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Correct boundary conditions for two inlets and two outlets

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Old   October 14, 2023, 07:57
Default Correct boundary conditions for two inlets and two outlets
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Hello everyone,

First of all, I want to thank those who will help in advance.

I have been struggling with a model for months, but I cannot determine the correct boundary conditions. The model is as shown below: cold water flows at the bottom from left to right, while hot water flows at the top from right to left. In other words, there are two inlets and two outlets in this case.

I am using buoyantPimpleFoam as a solver to find the thickness of the interface in the middle. To avoid turbulence effects, I use laminar model for turbulence properties; but eventually I am planning to solve with DES Model. There is velocity input at the inlets. When I give pressure to the outlets, I cannot achieve the desired flow. Since the distance is shorter, cold water exits from the hot water outlet, and hot water exits from the cold water outlet; in other words, there is a U-turn. After a short while, the simulation explodes. When I give the pressure to the top, after a while, the hot water wants to come out from the top. I have tried hundreds of boundary conditions, but unfortunately, I cannot find the correct boundary conditions for the flow to go directly across as I want.

I am sending the schematic drawing of my model and U-turn attached. Also the details of my fluids are as follows:

-Cold water: Velocity: 0.05 m/s, Temperature: 288 K
-Hot water: Velocity: 0.0375 m/s, Temperature: 323 K

-Thermophysical properties:
Quote:
thermoType
{
type heRhoThermo;
mixture pureMixture;
transport const;
thermo hConst;
equationOfState Boussinesq;
specie specie;
energy sensibleEnthalpy;
}

mixture
{
specie
{
molWeight 18;
}
equationOfState
{
rho0 999.1;
T0 288;
beta 3.1457e-4;
}
thermodynamics
{
Cp 418.5;
Hf 0;
}
transport
{
mu 1001.6e-6;
Pr 6.99;
}
}
If you need more details to understand my problem, I can provide more information. I would be very grateful for any solutions you can suggest.
Attached Images
File Type: png model.png (35.4 KB, 20 views)
File Type: jpg Uturn.jpg (112.6 KB, 12 views)
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