CFD Online Discussion Forums

CFD Online Discussion Forums (https://www.cfd-online.com/Forums/)
-   OpenFOAM Running, Solving & CFD (https://www.cfd-online.com/Forums/openfoam-solving/)
-   -   Unexpected direction of fluid flow (https://www.cfd-online.com/Forums/openfoam-solving/219388-unexpected-direction-fluid-flow.html)

rahulksoni July 25, 2019 05:15
Unexpected direction of fluid flow
 
4 Attachment(s)
Dear all
I am simulating the water flow through a screen (the screen which is a metal sheet with holes in it for the passage of fluid and/or particles).

Another similar post can be found at https://www.cfd-online.com/Forums/op...tml#post726778

Please refer to animation at https://www.dropbox.com/s/n2sc9nbgh9...ation.ogv?dl=0 or the attached snapshots.

The fluid flow has inlet velocity boundary condition from the top feeding area.
The left side is defined as a wall. The right and bottom opening are defined as the atmospheric boundary. It is a turbulent case with KOmegaSST model running with solver interFoam. The second phase in the system is ambient air. The front and back are the cyclic boundaries.

The velocity and pressure boundary conditions are as follows:
Velcoity
Code:
dimensions        [0 1 -1 0 0 0 0];

internalField        uniform (0.0 0.0 0.0);

boundaryField
{
        outlet
        {
                type                        pressureInletOutletVelocity;
                inletValue                uniform (0.0 0.0 0.0);
                value                        uniform (0.0 0.0 0.0);
                //type            inletOutlet;
        //inletValue      uniform (0 0 0);
        //value          uniform (0 0 0);
        }
        inlet
        {
                type                        flowRateInletVelocity;
                value                        uniform (0.0 0.0 0.0);
                volumetricFlowRate        constant 0.00207;//as per calculation in diary;//9.26E-6;
        //type            fixedValue;
        //value          uniform (0 0 -0.04655);
        }
        /*empty_walls
        {
                type                        empty;
        }*/
        front
        {
                type                        cyclic;
        }
        back
        {
                type                        cyclic;
        }
        Screen_topBlockage
        {
                type                        fixedValue;
                value                        uniform (0.0 0.0 0.0);
        }
        Screen_VFinal
        {
                type                        fixedValue;
                value                        uniform (0.0 0.0 0.0);
        }
    left_wall
    {
                type                        fixedValue;
                value                        uniform (0.0 0.0 0.0);
    }               
}
Pressure
Code:
dimensions        [1 -1 -2 0 0 0 0];

internalField        uniform 101325;

boundaryField
{
        outlet
        {
                type                totalPressure;
                p0                        uniform 101325;
                rho                        rho;
                phi                        rhoPhi;
                gamma                0;
        }
        inlet
        {
                type                fixedFluxPressure;
                //type                zeroGradient;
        }
        /*empty_walls
        {
                type                empty;
        }*/
        front
        {
                type                cyclic;
        }
        back
        {       
                type                cyclic;
        }
        Screen_topBlockage
        {
                type                fixedFluxPressure;
                //type                zeroGradient;
        }
        Screen_VFinal
        {
                type                fixedFluxPressure;
                //type                zeroGradient;
        }
    left_wall
    {
                type                fixedFluxPressure;
                //type                zeroGradient;
    }       
}
alpha.fluid
Code:
dimensions        [0 0 0 0 0 0 0];

internalField        uniform 0.0;

boundaryField
{
        outlet
        {
                type        zeroGradient;
                //type            inletOutlet;
        //inletValue      uniform 0;
        //value          uniform 0;
        }
        inlet
        {
                type        fixedValue;
                value        uniform 1.0;
        }
        /*empty_walls
        {
                type        empty;
        }*/
        front
        {
                type        cyclic;
        }
        back
        {
                type        cyclic;
        }
        Screen_topBlockage
        {
                type        zeroGradient;
        }
        Screen_VFinal
        {
                type        zeroGradient;
        }
        left_wall
        {
                type        zeroGradient;
        }
}
Other boundary files are attached.
Attachment 71304

Attachment 71305

Attachment 71306
Can anyone tell me why the fluid has the typical tendency to flow leftward where left plane is defined as a wall.

rahulksoni July 26, 2019 03:49
2 Attachment(s)
I have looked into the flow profiles closely. And, I guess it is because of the significant density difference between water and air in interFoam.
Please see the attached screenshots. It shows that as the water touches the solid body (metal screen) there is a splash. Which causes to replace air by water in leftward and rightward of splash. However, due to small space in left region, there is significant water circulation flows. Air gets high velocity because of the low density of it while compared with water. This high speed flow creates low pressure in the region which attracts water there.
Someone, please comment.
Attachment 71341

Attachment 71342

rahulksoni August 2, 2019 03:01
[solved]
 
1 Attachment(s)
I could solve the problem by reducing block height on the left side. I guess due to the small region for movement on the left, the circulation of air occurred probably with high speed and that reduced the pressure in the region.
This made suck the fluid in the left region leading to the observed dynamics.

After reducing the height of the block at top or in other words by increasing the open area the problem was solved. Please see the attached snapshot.


All times are GMT -4. The time now is 14:12.