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DEM Simulation not stable with a sphere in a cylinder
  • I am trying to simulate a falling sphere in a cylinder. But the sphere drifts in cylinder after touching the base of the cylinder.

    Thanks for the help.
    Regards

    ?xml version="1.0" encoding="UTF-8" ?>
    !-- Note:
    1. This section simulate the physics of falling spheres and saving those in seperate files.
    -->
    case>
    casedef>
    constantsdef>
    lattice bound="1" fluid="1" />
    gravity x="0" y="0" z="-9.81" comment="Gravitational acceleration" units_comment="m/s^2" />
    rhop0 value="1000" comment="Reference density of the fluid" units_comment="kg/m^3" />
    hswl value="0.8" auto="true" comment="Maximum still water level to calculate speedofsound using coefsound" units_comment="metres (m)" />
    gamma value="7" comment="Polytropic constant for water used in the state equation" />
    speedsystem value="0" auto="true" comment="Maximum system speed (by default the dam-break propagation is used)" />
    coefsound value="30" comment="Coefficient to multiply speedsystem" />
    speedsound value="0" auto="true" comment="Speed of sound to use in the simulation (by default speedofsound=coefsound*speedsystem)" />
    coefh value="1.2" comment="Coefficient to calculate the smoothing length (h=coefh*sqrt(3*dp^2) in 3D)" />
    cflnumber value="0.2" comment="Coefficient to multiply dt" />
    /constantsdef>
    mkconfig boundcount="230" fluidcount="10">
    mkorientfluid mk="0" orient="Xyz" />
    /mkconfig>
    geometry>
    definition dp="0.05">
    pointmin x="-2" y="-2" z="-1" />
    pointmax x="2" y="2" z="4" />
    /definition>
    commands>
    mainlist>
    setshapemode>dp | bound/setshapemode>
    setdrawmode mode="full" />
    setmkbound mk="0" />
    drawfilestl file="cyl.stl">
    /drawfilestl>
    shapeout file="cyl" />
    setmkbound mk="1" />
    drawfilestl file="sphere.stl">
    drawmove x="0" y="0" z="0.25" />
    /drawfilestl>
    shapeout file="sphere1" />
    /mainlist>
    /commands>
    /geometry>
    geometry>
    definition dp="0.05">
    pointmin x="-2" y="-2" z="-1" />
    pointmax x="2" y="2" z="4" />
    /definition>
    commands>
    mainlist>
    setshapemode>dp | bound/setshapemode>
    setdrawmode mode="full" />
    setmkbound mk="0" />
    drawfilestl file="cyl.stl">
    /drawfilestl>
    shapeout file="cyl" />
    setmkbound mk="1" />
    drawfilestl file="sphere.stl">
    drawmove x="0" y="0" z="0.25" />
    /drawfilestl>
    shapeout file="sphere1" />
    /mainlist>
    /commands>
    /geometry>
    floatings>
    floating mkbound="1" relativeweight="1" property="steel + userdef01" />
    massbody value="1300" />
    /floatings>
    properties>
    propertyfile file="Floating_Materials.xml" path="materials" />
    property name="userdef01" Restitution_Coefficient_User="0.70" comment="User redefinition for Restitution Coefficient (-)" />
    links>
    link mkbound="0" property="steel + userdef01" comment="Property for the tank" />
    /links>
    /properties>
    /casedef>
    execution>
    parameters>
    parameter key="PosDouble" value="1" comment="Precision in particle interaction 0:Simple, 1:Double, 2:Uses and saves double (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)" />
    parameter key="ViscoTreatment" value="1" comment="Viscosity formulation 1:Artificial, 2:Laminar+SPS (default=1)" />
    parameter key="Visco" value="0.01" comment="Viscosity value" />
    parameter key="ViscoBoundFactor" value="1" comment="Multiply viscosity value with boundary (default=1)" />
    parameter key="DeltaSPH" value="0.1" comment="DeltaSPH value, 0.1 is the typical value, with 0 disabled (default=0)" />
    parameter key="#Shifting" value="0" comment="Shifting mode 0:None, 1:Ignore bound, 2:Ignore fixed, 3:Full (default=0)" />
    parameter key="#ShiftCoef" value="-2" 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="2" comment="Rigid Algorithm 1:SPH, 2:DEM (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="DtIni" value="0.001" comment="Initial time step (default=h/speedsound)" units_comment="seconds" />
    parameter key="DtMin" value="0.00001" comment="Minimum time step (default=coefdtmin*h/speedsound)" units_comment="seconds" />
    parameter key="#DtFixed" value="DtFixed.dat" comment="Dt values are loaded from file (default=disabled)" />
    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="2" comment="Time of simulation" units_comment="seconds" />
    parameter key="TimeOut" value="0.02" comment="Time out data" units_comment="seconds" />
    parameter key="IncZ" value="1" comment="Increase of Z+" units_comment="decimal" />
    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="700" comment="Minimum rhop valid (default=700)" units_comment="kg/m^3" />
    parameter key="RhopOutMax" value="1300" comment="Maximum rhop valid (default=1300)" units_comment="kg/m^3" />
    !--parameter key="XPeriodicIncZ" value="1" comment="Periodic BC in X" /-->
    /parameters>
    /execution>
    /case>