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conical whirl (Precession) motion through mesh deformation technique

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Old   March 13, 2024, 02:35
Default conical whirl (Precession) motion through mesh deformation technique
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Boram Kim
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Hi, i have a problem with the following;

I'm trying to make conical whirl ( i added a picture for your understanding) motion through mesh deformation technique in journal bearing and seals. But it does not working.. i just keep making cylinerical motion T.T

1. Even though I try variously changing the options, the tilted axis is not adopted..it just show only cylinerical motion like pararell to global z axis. How do I make it rotate based on the new axis I created (coord 1.3)?

2. i want to make different motion at inlet and outlet(please refer to attatched picture) but i only kwow the way it rotate 3d surface through 'specified displacement'. How can i set the inner surfaces of the inlet and outlet seperatley move?

conical whirl.jpg
cylinderical whirl.PNG

Sincerly
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Old   March 13, 2024, 05:02
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Please attach your CCL.
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Old   March 13, 2024, 20:09
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Please check the information below..!

FLOW: Flow Analysis 1
&replace DOMAIN: seal
Coord Frame = Coord 0
Domain Type = Fluid
Location = seal
BOUNDARY: inlet
Boundary Type = INLET
Location = inlet
BOUNDARY CONDITIONS:
FLOW DIRECTION:
Option = Normal to Boundary Condition
END
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Static Pressure
Relative Pressure = 6 [MPa]
END
MESH MOTION:
Option = Parallel to Boundary
END
TURBULENCE:
Option = Medium Intensity and Eddy Viscosity Ratio
END
END
END
BOUNDARY: outlet
Boundary Type = OUTLET
Location = outlet
BOUNDARY CONDITIONS:
FLOW REGIME:
Option = Subsonic
END
MASS AND MOMENTUM:
Option = Static Pressure
Relative Pressure = 1 [MPa]
END
MESH MOTION:
Option = Parallel to Boundary
END
END
END
BOUNDARY: rotor
Boundary Type = WALL
Create Other Side = Off
Interface Boundary = Off
Location = rotor
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
Wall Velocity Relative To = Boundary Frame
WALL VELOCITY:
Option = Cartesian Components
Wall U = Vx
Wall V = Vy
Wall W = 0 [m s^-1]
END
END
MESH MOTION:
Option = Surface of Revolution
AXIS DEFINITION:
Option = Coordinate Axis
Rotation Axis = Coord 1.3
END
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
BOUNDARY: stator
Boundary Type = WALL
Create Other Side = Off
Interface Boundary = Off
Location = stator
BOUNDARY CONDITIONS:
MASS AND MOMENTUM:
Option = No Slip Wall
Wall Velocity Relative To = Boundary Frame
END
MESH MOTION:
Option = Stationary
END
WALL ROUGHNESS:
Option = Smooth Wall
END
END
END
DOMAIN MODELS:
BUOYANCY MODEL:
Option = Non Buoyant
END
DOMAIN MOTION:
Option = Stationary
END
MESH DEFORMATION:
Displacement Relative To = Initial Mesh
Option = Regions of Motion Specified
MESH MOTION MODEL:
Option = Displacement Diffusion
MESH STIFFNESS:
Option = Increase near Small Volumes
Stiffness Model Exponent = 2.0
REFERENCE VOLUME:
Option = Mean Control Volume
END
END
END
END
REFERENCE PRESSURE:
Reference Pressure = 1 [atm]
END
END
FLUID DEFINITION: Fluid 1
Material = Air at 25 C
Option = Material Library
MORPHOLOGY:
Option = Continuous Fluid
END
END
FLUID MODELS:
COMBUSTION MODEL:
Option = None
END
HEAT TRANSFER MODEL:
Fluid Temperature = 25 [C]
Option = Isothermal
END
THERMAL RADIATION MODEL:
Option = None
END
TURBULENCE MODEL:
Option = SST
END
TURBULENT WALL FUNCTIONS:
Option = Automatic
END
END
END
END
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Old   March 13, 2024, 21:06
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If the axis of rotation does not change then I would not use a mesh motion approach, I would use a rotating frame of reference (with a transient rotor stator interface).

If the axis of rotation changes then you have to use moving mesh, but you have to define the motion of the boundaries yourself. For a whirling motion this will be complex function of the rotation combined with the whirl.
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annular seal, cfx, conical motion, journal bearing, mesh deformation

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