Community Computational Fluid Dynamics OpenLabs Actuator disk modeling in OpenLabs

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Actuator disk modeling in OpenLabs

Colinda

To avoid meshing a full propeller, using an actuator disk model may be more suited to save cell count. The validity of such approximation depends of course on the objectives of the simulation and the required accuracy.

The actuator model adds source terms to the Navier-Stokes equations.

  • An example of such lab for an Actuator Disk Propeller without self-update is given here.

    The constants section contains the user defined variables that can be adapted to the test case.

    LIMITATIONS:

    • Only a source term in the momentum equation in the X direction is considered.
    • This example does not involve any self-update.
    • Only the cells for which the cell center coordinates are within the geometrical condition will account for the source term.

    =>CONSTANTS

    #User defined variables
    @Rp=0.01
    @Rh=0.000
    @rpm=250
    @delta=0.02
    @Xpc=0.50
    @Ypc=0.05
    @Zpc=0.05
    @Uref=10.0
    @L=0.1

    @T0=0.1
    @Q0=0.0
    #--------------------------

    @PI=3.14159265359


    =>EQUATIONS


    @NONDIFFEXPR: Exprfbx
    ->EXPRESSION: fbx = IF(r<Rp AND xCoord>(Xpc-delta*0.5) AND xCoord<(Xpc+delta*0.5) ) Ax*rst*sqrt(1-rst) \
    ELSE 0.0

    @NONDIFFEXPR: Exprfbf
    ->EXPRESSION: fbf = IF(r<Rp AND xCoord>(Xpc-delta*0.5) AND xCoord<(Xpc+delta*0.5) ) Af*rst*sqrt(1-rst)/(rst*(1-rhprime)+rhprime)\
    ELSE 0.0


    =>INITIAL_PROFILES

    =>SOURCETERMS

    @ SOURCE: sourceToMomX
    ->EXPRESSION: (fbx) * (Rho*Uref*Uref/L)
    ->AddToExistingPde: MomentumXEquation


    =>CUSTOM_FLUID_PROPERTIES

    =>AUXTERMS

    @n=rpm/60.
    @Dp=2.0*Rp
    @J=Uref/(n*Dp)
    @r=sqrt((yCoord-Ypc)*(yCoord-Ypc)+(zCoord-Zpc)*(zCoord-Zpc))

    @Rho=Density

    @CT=2*T/(Rho*Uref*Uref*PI*Rp*Rp)
    @KT=T/(Rho*n*n*Dp*Dp*Dp*Dp)
    @KQ=Q/(Rho*n*n*Dp*Dp*Dp*Dp*Dp)

    @rprime=r/Rp
    @rhprime=Rh/Rp
    @rst=(rprime-rhprime)/(1.0-rhprime)

    @aux=105./((4.0+3.0*rhprime)*(1.0-rhprime))/delta

    @T=T0
    @Q=Q0/T0*T

    @Ax=CT*aux/16.
    @Af=KQ*aux/(J*J*PI)

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