Modelling Air gap between two concentric cylinders

Jagan Adithya Elango
Jagan Adithya Elango Altair Community Member
edited August 2022 in Community Q&A

I'm trying to model a air gap between stator and rotor of motor where the stator and rotor are concentric cylinders and air is present in the annular space. The circumferential wall of the inner cylinder is specified as moving wall with the tangential velocity of 47m/s ( according to the rotor's speed of 6000rpm)

But the velocity contours i got isn't meaningful, no slip effect is not found. The maximum velocity I got is around 2900m/s which is much higher the velocity of moving wall.

 

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I have attached my input file and post images for reference. Please let me what's wrong with my model/ boundary conditions. Thanks.

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Answers

  • acupro
    acupro
    Altair Employee
    edited August 2022

    This is the relevant Simple Boundary Condition from the input file:

    SIMPLE_BOUNDARY_CONDITION( "mw" ) {
    surface_sets = { "agkvalidation.SurfaceSet_4_1.tria3.airgap.wedge6","agkvalidation.SurfaceSet_4_2.tria3.rotor.tet4" }
    type = wall
    precedence = 1
    wall_velocity_type = cylindrical
    axial_velocity = 0
    radial_velocity = 0
    tangential_velocity = 47
    heat_flux = 0
    convective_heat_coefficient = 0
    convective_heat_reference_temperature= 273.16
    turbulence_wall_type = wall_function
    roughness_height = 0
    wall_function_friction_factor = 1
    wall_function_heat_flux_factor = 1
    active_type = all
    split_internal_surfaces = off
    mesh_displacement_type = none
    }

    As there is no definition for the cylinder axis, it is assumed (by the defaults) to have the endpoints 0,0,0 and 0,1,0. The direction is based on those two points, and the right-hand rule. In HyperWorks CFD, there is an 'Edit' button next to 'Cylinder Axis' in the Moving Wall boundary definition panel, where you can enter the correct pair of points.

    (Another approach would be to define a reference frame, but apply it only to the rotating surface(s) and not to any volume/solid.)

    You also need to make sure the dimensions of the meshed model are consistent with your values entered for materials, boundary conditions, etc.  You can use the Measure Tool, or look at the min/max values for X/Y/Z in the Log file.

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