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AxiSym laminar impinging free surface jet

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Old   December 18, 2016, 09:09
Default AxiSym laminar impinging free surface jet
  #1
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Ron
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Greetings FOAMers!
As the title suggests, I have some difficulties simulating an axisymmetrical free surface (liquid in gas) impinging jet. More specifically, with the outlet boundary conditions. I’m solving using interFoam.

Issue 1:
Currently, my jet flows along the x axis, hits the right wall and attempts to continue radially (y axis) towards the domain’s outlet. As the jet touches the boundary, the jet seems to view it as a “wall” (attached figure 1). I’ll note that up until the interaction with the outlet, it matches the literature.

0\p_rgh:
Code:
 dimensions      [1 -1 -2 0 0 0 0];
 internalField   uniform 0;
 boundaryField
 {
     inlet
     { type            zeroGradient;
     }
     outlet
     {  type            totalPressure;
         p0              uniform 0;
     }
     atmo
     {  type            totalPressure;
         p0              uniform 0;
     }
     walls
     {  type            fixedFluxPressure;
     }
     front
     {  type        wedge;
     }
     back
     { type        wedge;
     }
     axis
     { type        empty;
     }
 }
0\U:
Code:
dimensions      [0 1 -1 0 0 0 0];
 internalField   uniform (0 0 0);
 boundaryField
 {
     inlet
     {  type            uniformFixedValue;
         outOfBounds    clamp;
         uniformValue    table    2 (  (0.0    (0.00 0 0))
                      (0.00001    (1.667 0 0))    ); \\start-up condition\\
     }
     outlet
     { type            inletOutlet;
        inletValue      uniform (0 0 0);
         value           uniform (0 0 0); \\also tried here pressureInletOutletVelocity - same results\\
     }
     atmo
     {  type            pressureInletOutletVelocity;
         value           uniform (0 0 0);
     }        
     walls
     {  type            noSlip;
     }
     front/back: wedge and axis: empty
0\alpha.water
Code:
dimensions      [0 0 0 0 0 0 0];
 internalField   uniform 0;
 boundaryField
 {
     walls
     { type            zeroGradient;
     }
     inlet
     { type            fixedValue;
         value           uniform 1;
     }
     outlet
     {type            inletOutlet;  \\ also tried zeroGradient – continue reading:)
       inletValue      uniform 0;
       value      uniform 0;   
     }
     atmo
     { type            inletOutlet;
        inletValue      uniform 0;
        value      uniform 0;
     }
     front/back: wedge and axis: empty
g:
Code:
dimensions      [0 1 -2 0 0 0 0];
 value           (9.81 0 0);
Transport properties:
Code:
phases (water air);
 water
 {  transportModel  Newtonian;
     nu              [0 2 -1 0 0 0 0] 1e-06;
     rho             [1 -3 0 0 0 0 0] 1000;
 }
 air
 {  transportModel  Newtonian;
     nu              [0 2 -1 0 0 0 0] 1.48e-05;
     rho             [1 -3 0 0 0 0 0] 1;
 }
 sigma           [1 0 -2 0 0 0 0] 0.00;
Changing the alpha.water outlet boundary condition to zeroGradient seems to basically open the gates of hell as soon as a single drop touches the outlet (attached figure 2).


Issue 2:
The case above imposed 0 surface tension. When inputting a realistic water/air surface tension (sigma=0.07), the jet merely thickens at the impingement point, without attempting to flow outside of the domain (attached figure 3).


Thanks a lot for taking the time to read and think about my case,
Ron
Attached Images
File Type: png fig1a.png (39.7 KB, 35 views)
File Type: jpg fig2.jpg (38.4 KB, 34 views)
File Type: png fig3.png (14.4 KB, 31 views)
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Old   December 26, 2016, 06:11
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Ron
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So, I solved my first issue.

The problem was with the assumption that the outlet pressure is atmospheric (and well, equal to the other "free" surfaces of the domain).
Zero Gradient in all three (pressure, velocity and void function) as an outlet condition seems to work quite well.

Still working on the second one.

Ron
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Tags
impingement, interfoam, jet, outlet boundary condition, two phase

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