Problem with the code

Please, I need help with this simulation.

I have a problem in the code, after 4 minutes the simulation starts malfunctioning with the particles disappearing and I don't know why.

That is the code:

<special>

<shifting>

<mode value="3" comment="Shifting mode 0:None, 1:Ignore bound, 2:Ignore fixed, 3:Full" />

<coefficient value="-50" comment="Coefficient for shifting computation (default=-2)" />

<fsthreshold value="1.5" comment="Threshold to detect free surface. Typically 1.5 for 2D and 2.75 for 3D (default=0)" />

<shiftingzone>

<posref x="0" y="0" z="0.2" comment="Domain reference position" />

<size x="2" y="0" z="0.6" comment="Size from reference to define shifting domain" />

</shiftingzone>

</shifting>

</special>

</special>

     <parameters>

      <parameter key="SavePosDouble" value="0" comment="Saves particle position using double precision (default=0)" />

      <parameter key="StepAlgorithm" value="2" comment="Step Algorithm 1:Verlet, 2:Symplectic (default=1)" />

      <parameter key="VerletSteps" value="40" comment="Verlet only: Number of steps to apply Euler timestepping (default=40)" />

      <parameter key="Kernel" value="2" comment="Interaction Kernel 1:Cubic Spline, 2:Wendland (default=2)" />


%Choice of reology treatment, velocity gradient calculation and viscosity treatment  


<parameter key="RheologyTreatment" value="2" comment="Reology formulation 1:Single-phase classic, 2: Single and multi-phase" />       

<parameter key=" VelocityGradientType" value="1" comment="Velocity gradient formulation 1:FDA, 2:SPH" />

      <parameter key="ViscoTreatment" value="2" comment="Viscosity formulation 1:Artificial, 2:Laminar+SPS, 3:Constitutive eq." />      

 

%Wall boundary viscosity or/and artificial viscosity if ViscoTreatment is 1:Artificial

 

<parameter key="Visco" value="0.05" comment="Viscosity value" /> % Note alpha can depend on the resolution when using artificial viscosity

      <parameter key="ViscoBoundFactor" value="1" comment="Multiply viscosity value with boundary (default=1)" />

      <parameter key="DensityDT" value="3" comment="Density Diffusion Term 0:None, 1:Molteni, 2:Fourtakas, 3:Fourtakas(full) (default=0)" />

      <parameter key="DensityDTvalue" value="0.1" comment="DDT value (default=0.1)" />

      <parameter key="Shifting" value="3" comment="Shifting mode 0:None, 1:Ignore bound, 2:Ignore fixed, 3:Full (default=0)" />

      <parameter key="ShiftCoef" value="-50" comment="Coefficient for shifting computation (default=-2)" />

<parameter key="ShiftTFS" value="1.5" comment="Threshold to detect free surface. Typically 1.5 for 2D and 2.75 for 3D (default=0)" />

      <parameter key="RigidAlgorithm" value="1" comment="Rigid Algorithm 0:collision-free, 1:SPH, 2:DEM, 3:Chrono (default=1)" />

      <parameter key="FtPause" value="0.0" comment="Time to freeze the floatings at simulation start (warmup) (default=0)" units_comment="seconds" />

      <parameter key="CoefDtMin" value="0.05" comment="Coefficient to calculate minimum time step dtmin=coefdtmin*h/speedsound (default=0.05)" />

      <parameter key="RelaxationDt" value="0.2" comment="Relaxation parameter for the viscous time step restricition(default=0.2)" />

<parameter key="DtIni" value="0" comment="Initial time step. Use 0 to defult use (default=h/speedsound)" units_comment="seconds" />

      <parameter key="DtMin" value="0" comment="Minimum time step. Use 0 to defult use (default=coefdtmin*h/speedsound)" units_comment="seconds" />

      <parameter key="DtFixed" value="0" comment="Fixed Dt value. Use 0 to disable (default=disabled)" units_comment="seconds" />

      <parameter key="DtFixedFile" value="NONE" comment="Dt values are loaded from file. Use NONE to disable (default=disabled)" units_comment="milliseconds (ms)" />

      <parameter key="DtAllParticles" value="0" comment="Velocity of particles used to calculate DT. 1:All, 0:Only fluid/floating (default=0)" />

      <parameter key="TimeMax" value="390.0" comment="Time of simulation" units_comment="seconds" />

      <parameter key="TimeOut" value="0.1" comment="Time out data" units_comment="seconds" />

      <parameter key="PartsOutMax" value="1" comment="%/100 of fluid particles allowed to be excluded from domain (default=1)" units_comment="decimal" />

      <parameter key="RhopOutMin" value="500" comment="Minimum rhop valid (default=700)" units_comment="kg/m^3" />

      <parameter key="RhopOutMax" value="3000" comment="Maximum rhop valid (default=1300)" units_comment="kg/m^3" />

<parameter key="XPeriodicIncZ" value="0" comment="Increase of Z with periodic BC" />

      <simulationdomain comment="Defines domain of simulation (default=Uses minimun and maximum position of the generated particles)">

        <posmin x="default" y="default" z="default" comment="e.g.: x=0.5, y=default-1, z=default-10%" />

        <posmax x="default" y="default" z="default + 50%" />

</simulationdomain>

    </parameters>

  </execution>

</case>

Comments

  • Have you visualized your simulation?

    What exactly happens and at what time step?

    Have you tried to play around with the amount of fluid and see if it fixes the issue?

    What is the warning you get / where do the particles leave?

    Another good piece of advice is starting from an example very similar to yours and then change it step by step.

    Kind regards

  • Thanks a lot !!!💪

    Have you visualized your simulation?

    • Yes I did.

    What exactly happens and at what time step?

    • 4 minutes in after starting the simulation, coming the white zone = don't have particules

    Have you tried to play around with the amount of fluid and see if it fixes the issue?

    • I tried to change everything, mainly with the shifting coefficient.

    What is the warning you get / where do the particles leave?

    • No warning, only after 4 minutes, blank zone parts = without particules.

    Another good piece of advice is starting from an example very similar to yours and then change it step by step.

    • Thanks for the advice, I got here like this. But could you give me some examples, so I review it?

    Thank for the 

    Kind regards


  • Try this one and play with shifting values / time stepping.

    Kind regards

  • Thanks a lot for your time @Asalih3d , but I can not associate the example with my works.

    Kind regards

  • No problem, else have a look at the other pdf files with examples perhaps there are some there. Perhaps someone else can help when they see it too

    Kind regards

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