[tonnykz]

Hello to everyone,
As I've mentioned in my previous thread (chtMultiRegionFoam with multiple liquid regions) I am using OF6 for my research project, aims of which to model gas-water interaction involving heat transfer, chemical kinetics, mass transport. I was trying to use chtMultiRegionFoam and got stuck with multiple problems:
1. Gas doesn't drag water. Tried various BC between regions.
2. Chemical species can't diffuse into neighbor region.
3. Can't have inter-region chemical reactions.
4. Pressure and velocity diverging. What bothers me most.

So, currently (with the advice of Robin.Kamenicky) I have switched to reactingTwoPhaseEulerFoam. Which should be able to solve my case correctly.

Simulation domain consists of two fluids: gas, flowing from left to right with defined velocity, on top of the water, that is still initially and dragged by gas. Dimensions of whole domain are 60mm x 30 mm x 0.1 mm. Inlet velocity is 0.1 m/s. Reynolds number in my case is quite high ~ 20400. Future steps will be adding chemical species in phases and reactions.
But, my simulations are diverging.
Schematics and case files are included.
I have several assumptions about causes that I am checking:
1. The way I defined mesh as consisting of two blocks.
2. Sharp interface between gas and flow causing divergence.

3. Incorrect BCs.


Any help/hints/advises will be appreciated, thanks in advance!

Initial fields:

T.water:
dimensions [0 0 0 1 0 0 0];
internalField uniform 360;
boundaryField
{
inlet_gas
{
type fixedValue;
value $internalField;
}
outlet_gas
{
type inletOutlet;
phi phi.water;
inletValue $internalField;
value $internalField;
}
inlet_liquid
{
type fixedValue;
value $internalField;
}
outlet_liquid
{
type inletOutlet;
phi phi.water;
inletValue $internalField;
value $internalField;
}
top_gas
{
type zeroGradient;
}
bottom_liquid
{
type zeroGradient;
}
}

T.steam:
dimensions [0 0 0 1 0 0 0];
internalField uniform 360;//372.76;
boundaryField
{
inlet_gas
{
type fixedValue;
value $internalField;
}
outlet_gas
{
type inletOutlet;
phi phi.steam;
inletValue $internalField;
value $internalField;
}
inlet_liquid
{
type fixedValue;
value $internalField;
}
outlet_liquid
{
type inletOutlet;
phi phi.steam;
inletValue $internalField;
value $internalField;
}
top_gas
{
type zeroGradient;
}
bottom_liquid
{
type zeroGradient;
}
}

U.water:
dimensions [0 1 -1 0 0 0 0];
internalField uniform (0.1 0 0);
boundaryField
{
inlet_gas
{
type fixedValue;
value uniform (0.1 0 0);
}
outlet_gas
{
type pressureInletOutletVelocity;
phi phi.water;
value $internalField;
}
inlet_liquid
{
type fixedValue;
value uniform (0.1 0 0);
}
outlet_liquid
{
type pressureInletOutletVelocity;
phi phi.water;
value $internalField;
}
top_gas
{
type noSlip;
}
bottom_liquid
{
type noSlip;
}
}

U.steam:
dimensions [0 1 -1 0 0 0 0];
internalField uniform (0.1 0 0);
boundaryField
{
inlet_gas
{
type fixedValue;
value uniform (0.1 0 0);
}
outlet_gas
{
type pressureInletOutletVelocity;
phi phi.steam;
value $internalField;
}
inlet_liquid
{
type fixedValue;
value uniform (0.1 0 0);
}
outlet_liquid
{
type pressureInletOutletVelocity;
phi phi.steam;
value $internalField;
}
top_gas
{
type noSlip;
}
bottom_liquid
{
type noSlip;
}
}

p:
dimensions [ 1 -1 -2 0 0 0 0 ];
internalField uniform 1e5;
boundaryField
{
inlet_gas
{
type calculated;
value $internalField;
}
outlet_gas
{
type calculated;
value $internalField;
}
inlet_liquid
{
type calculated;
value $internalField;
}
outlet_liquid
{
type calculated;
value $internalField;
}
top_gas
{
type calculated;
value $internalField;
}
bottom_liquid
{
type calculated;
value $internalField;
}
}

p_rgh:
dimensions [ 1 -1 -2 0 0 0 0 ];
internalField uniform 1e5;
boundaryField
{
inlet_gas
{
type fixedFluxPressure;
value $internalField;
}
outlet_gas
{
type prghPressure;
p $internalField;
value $internalField;
}
inlet_liquid
{
type fixedFluxPressure;
value $internalField;
}
outlet_liquid
{
type prghPressure;
p $internalField;
value $internalField;
}
top_gas
{
type fixedFluxPressure;
value $internalField;
}
bottom_liquid
{
type fixedFluxPressure;
value $internalField;
}
}

water.water:
dimensions [0 0 0 0 0 0 0];
internalField uniform 1;
boundaryField
{
inlet_gas
{
type fixedValue;
value uniform 0;
}
outlet_gas
{
type inletOutlet;
phi phi.water;
inletValue uniform 0;
// value $internalField;
}
inlet_liquid
{
type fixedValue;
value uniform 1;
}
outlet_liquid
{
type inletOutlet;
phi phi.water;
inletValue $internalField;
value $internalField;
}
top_gas
{
type zeroGradient;
}
bottom_liquid
{
type zeroGradient;
}
}

water.steam:
dimensions [0 0 0 0 0 0 0];
internalField uniform 1;
boundaryField
{
inlet_gas
{
type fixedValue;
value uniform 1;
}
outlet_gas
{
type inletOutlet;
phi phi.steam;
inletValue $internalField;
value $internalField;
}
inlet_liquid
{
type fixedValue;
value uniform 0;
}
outlet_liquid
{
type inletOutlet;
phi phi.steam;
inletValue uniform 0;
// value $internalField;
}
top_gas
{
type zeroGradient;
}
bottom_liquid
{
type zeroGradient;
}
}

alpha.water:
dimensions [0 0 0 0 0 0 0];
internalField uniform 0;
boundaryField
{
inlet_gas
{
type fixedValue;
value uniform 0;
}
outlet_gas
{
type inletOutlet;
phi phi.water;
inletValue uniform 0;
value uniform 0;
}
inlet_liquid
{
type fixedValue;
value uniform 1;
}
outlet_liquid
{
type inletOutlet;
phi phi.water;
inletValue uniform 1;
value uniform 1;
}
top_gas
{
type zeroGradient;
}
bottom_liquid
{
type zeroGradient;
}
}

alpha.steam:
dimensions [0 0 0 0 0 0 0];
internalField uniform 1;
boundaryField
{
inlet_gas
{
type fixedValue;
value uniform 1;
}
outlet_gas
{
type inletOutlet;
phi phi.steam;
inletValue uniform 1;
value uniform 1;
}
inlet_liquid
{
type fixedValue;
value uniform 0;
}
outlet_liquid
{
type inletOutlet;
phi phi.steam;
inletValue uniform 0;
value uniform 0;
}
top_gas
{
type zeroGradient;
}
bottom_liquid
{
type zeroGradient;
}
}

nut:
dimensions [0 2 -1 0 0 0 0];
internalField uniform 1e-8;
boundaryField
{
inlet_gas
{
type calculated;
value $internalField;
}
outlet_gas
{
type calculated;
value $internalField;
}
inlet_liquid
{
type calculated;
value $internalField;
}
outlet_liquid
{
type calculated;
value $internalField;
}
top_gas
{
type nutkWallFunction;
value $internalField;
}
bottom_liquid
{
type nutkWallFunction;
value $internalField;
}
}

[tonnykz]

I think I found an answer to my question from this Boundary conditions for Two-phase Flow with Different Inlet Pressures thread.
As I've been imposing different BC for two regions there is always the gradient of field. Therefore, my simulations kept diverging.
Now, I moved to formulation of single region (as single 2D pipe), and took the injection and fluidisedBed tutorials from multiphase/reactingTwoPhaseEulerFoam/laminar in OF6.

Hope that will help someone.

[yizzf]

Originally Posted by tonnykz

I think I found an answer to my question from this Boundary conditions for Two-phase Flow with Different Inlet Pressures thread.
As I've been imposing different BC for two regions there is always the gradient of field. Therefore, my simulations kept diverging.
Now, I moved to formulation of single region (as single 2D pipe), and took the injection and fluidisedBed tutorials from multiphase/reactingTwoPhaseEulerFoam/laminar in OF6.

Hope that will help someone.

Thanks for helping me too