Numerical Simulation of Free Surface over Spillway

In this post, i presented my simulation of free surface over cylindrical spillway using OpenFOAM solver (interFoam).
following steps are conducted for preparing case:

Create grid with OpenFOAM mesh generators


  • generate base grid with blockMesh
  • extract spillway from base grid and refine locally around spillway with snappyHexMesh
  • extrude front patch to create 2D grid for simulation

The extrudeMeshDict setup is:

constructFrom patch;
sourceCase ".";
sourcePatches (front);

exposedPatchName back;

flipNormals false;

extrudeModel linearNormal;

nLayers 1;

expansionRatio 1.0;

linearNormalCoeffs
{
 thickness 0.1;
}
mergeFaces false;
mergeTol 0;

snappyHexMesh divides cells in z direction which is not suitable for 2D simulation. Thus extrudeMesh extrudes the front patch, so the final grid have only one cell in z direction. The final grid is shown below:

grid around cylindrical spillway is created with OpenFOAM utilities: blockMesh, snappyHexMesh and extrudeMesh

Simulation settings and result


  • apply setFields to create non-uniform initial condition for volume fraction
  •  apply blank roughness using wall function nutRoughWallFunction via turbulence model
  •  run solver interFoam
  • add appropriate functions  into controlDict via swak4Foam for post processing. For example, the depth of water over spillway crest is calculated as follow:
depthOverCrest
 {
 type     swakExpression;
 valueType    set;
 verbose    true;
 setName    yb1;
 set
 {
 type    uniform;
 axis    y;
 start   ( 0 -0.175 -0.15 );
 end     ( 0  0.175 -0.15 );
 nPoints   60;
 }
 aliases  { alpha1  alpha.water; }
 expression "(alpha1 > 0.5) ? pos().y+0.175 :0";
 accumulations (max);
 interpolate   true;
 interpolationType   cellPoint ;
 outputControlMode   timeStep;
 outputInterval   1;
 }
simulation of free surface on spillway using interFoam
simulation of free surface on spillway using interFoam

For inlet, variableHeightFlowRate  and variableHeightFlowRateInletVelocity is employed for alpha.water and velocity, respectively. These BCs consider the effect of down stream on the patch.

2 Replies to “Numerical Simulation of Free Surface over Spillway”

Leave a Reply

Your email address will not be published. Required fields are marked *