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Problems with a barrier in a river

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Old   July 3, 2014, 04:24
Default Problems with a barrier in a river
  #1
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matthias
Join Date: Jul 2014
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Hi;
I want to analyze a river streaming over a barrier as in the picture below


I've created the "river" as one block (13,0m * 0,4m * 0,5m) and putted the barrier as .stl data in the middle of my bock.

Also, I have created some inlet_patch (snappyHexMeshDict) at the beginning of my block as my water inlet:

Quote:
inlet_patch
{
type searchablePlate;
origin (4 0 -0.3);
span (0 0.04 0.3);
}
Because I want to have the same water-level (0.30m) at the beginning as at the end of my box, I pushed my whole mesh 30 cm down and use this BC at the outlet:

Quote:
outlet
{
type totalPressure;
p0 uniform 0;
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;
I want to simulate that the water-level sinks over and rises after the barrier. In my results I can see the sinking but after that there are many waves and stuff like that.
I've tried to change the mesh in 2D, played with different verlocities and things like this, but the problem ist still the same.

You can find the conent of my inter/0 folder below - maybe somebody can help me.

Thanks
faerber

alpha.water:
Quote:
boundaryField
{
inlet_patch
{
type fixedValue;
value uniform 1;
}
inlet_wall
{
type zeroGradient;
}
outlet
{
type zeroGradient;
}
boden
{
type zeroGradient;
}
walls
{
type slip;
}
atmosphere
{
type inletOutlet;
inletValue uniform 0;
value uniform 0;
}
schwelle
{
type zeroGradient;
}
}
U:
Quote:
boundaryField
{
inlet_patch
{
type flowRateInletVelocity;
volumetricFlowRate constant 0.007; // m³/s

value uniform (0 0 0);


}
inlet_wall
{


type fixedValue;
value uniform (0 0 0);


}
outlet
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}
boden
{
type fixedValue;
value uniform (0 0 0);
}
walls
{
type slip;

}
atmosphere
{
type pressureInletOutletVelocity;
value uniform (0 0 0);
}
schwelle
{
type fixedValue;
value uniform (0 0 0);
}
}


// ************************************************** *********************** //
p_rgh:
Quote:
boundaryField
{
inlet_patch
{
type fixedFluxPressure; //früher: buoyantPressure;
value uniform 0;
}
inlet_wall
{
type fixedFluxPressure; //früher: buoyantPressure;
value uniform 0;
}
outlet
{
type totalPressure;
p0 uniform 0;
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;
}
boden
{
type fixedFluxPressure; //früher: buoyantPressure;
}
walls
{
type slip;
}
atmosphere
{
type totalPressure;
p0 uniform 0;
U U;
phi phi;
rho rho;
psi none;
gamma 1;
value uniform 0;
}
schwelle
{
type fixedFluxPressure; //früher: buoyantPressure;
}
}
k:
Quote:
boundaryField
{
inlet_patch
{
type inletOutlet;
inletValue uniform 0.001;
value uniform 1e-11;
}
inlet_wall
{
type fixedValue;
value uniform 1e-11;
}
outlet
{
type fixedValue;
value uniform 1e-11;
}
boden
{
type fixedValue;
value uniform 1e-11;
}
walls
{
type slip;
}
atmosphere
{
type inletOutlet;
inletValue uniform 0.001;
value uniform 1e-11;
}
schwelle
{
type fixedValue;
value uniform 1e-11;
}
}
nuSgs:
Quote:
boundaryField
{
inlet_patch
{
type zeroGradient;
}
inlet_wall
{
type zeroGradient;
}
outlet
{
type zeroGradient;
}
boden
{
type zeroGradient;
}
walls
{
type slip;
}
atmosphere
{
type zeroGradient;
}
schwelle
{
type zeroGradient;
}
}
nuTilda:
Quote:
boundaryField
{
outlet
{
type zeroGradient;
}
inlet_patch
{
type zeroGradient;
}
inlet_wall
{
type zeroGradient;
}
boden
{
type fixedValue;
value uniform 0;
}
walls
{
type slip;
}
atmosphere
{
type zeroGradient;
}
schwelle
{
type fixedValue;
value uniform 0;
}
}
Attached Images
File Type: jpg case.jpg (12.4 KB, 27 views)
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Old   July 6, 2014, 08:44
Default
  #2
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matthias
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Here are my used mesh and inter files:
https://www.dropbox.com/s/jfondecyyttsxn0/case.zip
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Old   July 6, 2014, 22:29
Default
  #3
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Matthew Denno
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Posts: 138
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Hi Matthias,

Controlling the water level at the outlet of the domain is something that I have had trouble with for some time. It doesn't seem that there is a universal solution available. I think the best approach depends on the specific case.

Check out this thread for one solution:
http://www.cfd-online.com/Forums/ope...tml#post390371

Also, although I haven't tried it yet there is a phaseHydrostaticPressure boundary condition that may work well for a fixed water level outlet...maybe used with groovyBC to specify where alpha changes from 1 to 0 (i.e. the water level)....

Matt
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