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Introduction

We learn how to use VOF model of Wildkatze solver with the help of famous Dambreak test problem. Here a column of water collapses and water surface is tracked by VOF model.

We demonstrate how efficiently Wildkatze performs multi-phase simulation thanks to its Implicit VOF model.

Here we decide the maximum time-step based on Maximum Courant number = 10. Typically VOF models find it tough to run even at Courant number = 1 or so. Time-step based on Maximum Courant number = 10 is extremely challenging for any solver but here Wildkatze makes it look very easy and simple.

Dambreak



Basic Set up

Wildkatze can set up basic set up just by single command so that user does not have to spend time setting up case with GUI. It is almost always advised to use command line to set up the cases with Wildkatze. Advanced simulations could be set up with GUI too. For most cases command line set up is adequate.


solver.sh -lc vof dambreak -gr -vdt 1E-2 -pptr   -lc pf o.txt



Specialize the Set Up File output.stree

We edit output.stree file on a text editor.

Maximum Iterations Per Time-Step



     1  Noname
     23
       simulation-type    	transient 	0 	2 	steady 	transient User
       iteration    	Integer 	1 	1 	0 User
       timeIteration    	Integer 	1 	1 	0 User
       current-inner-iteration    	Integer 	1 	0 	0 User
       max-iterations    	Integer 	1 	1 	0 User
       max-iteration-per-timestep    	Integer 	1 	9 	0 User



Initialize Water Column

We initialize the water column by editing VariableBoxPatchItem in output.stree.


              (: 
              "VariableBoxPatchItem"  1  "volume-fraction(prim-phase,0.0,-1.0E+20,1.0E+20,-1.0E+20,1.0E+20,-1.0E+20,1.0E+20)"  "SimTreeBaseItem-plus-980-parent-FieldVariableItem978"    980  0  0

volume-fraction
prim-phase
1
-1e+20  -0.15
-1e+20  0.3
-1e+20  1e+20



Results Export Frequency

We edit PostProcessExportItem to set the results export frequency to 0.01 seconds.



zDataPP  
Time-Step  
Ensight-Gold  
Time-frequency  
0  
1000000  
0  
1e+06  
100  
0.01



Performing the Simulation

Performing the simulation is very easy. 

solver.sh -lc pf run.txt   -lc iterate 1000



Results

The results are exported in Ensight Gold format.

We have:

At time = 0.25 sec

At time = 0.525 sec

At time = 3.5 sec

At time = 8.0 sec