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Step 7: Boundary Conditions

figure Boundary Conditions

figure

1.   Specify rotational periodicity for the periodic boundary of the rotor ( periodic-11).

figure Boundary Conditions figure figure periodic-11 figure Edit...

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(a)   Select Rotational in the Periodic Type list.

(b)   Click OK to close the Periodic dialog box.

2.   Specify rotational periodicity for the periodic boundary of the stator ( periodic-22).

figure Boundary Conditions figure figure periodic-22 figure Edit...

figure

(a)   Select Rotational in the Periodic Type list.

(b)   Click OK to close the Periodic dialog box.

3.   Set the conditions for the pressure inlet of the rotor ( pressure-inlet-rotor).

figure Boundary Conditions figure figure pressure-inlet-rotor figure Edit...

figure

(a)   Select Direction Vector from the Direction Specification Method drop-down list.

(b)   Enter 0 for X-Component of Flow Direction.

(c)   Enter -1 for Z-Component of Flow Direction.

(d)   Select Intensity and Hydraulic Diameter from the Specification Method drop-down list.

(e)   Enter 1% for Turbulence Intensity and 0.074 m for Hydraulic Diameter.

  You will use $P_0 = 0$ gauge to model ambient conditions. The turbulence level is assumed to be low (1%) and the hydraulic diameter is used as the length scale.

(f)   Click OK to close the Pressure Inlet dialog box.

4.   Retain the default settings for the pressure inlet of the stator ( pressure-inlet-stator).

figure Boundary Conditions figure figure pressure-inlet-stator figure Edit...

  The profiles computed at the rotor outlet are used to update the boundary conditions at the stator inlet. These profiles were set automatically when the mixing plane was created. Therefore, you do not need to set any parameters in this dialog box.

figure

(a)   Click OK to close the Pressure Inlet dialog box.

5.   Retain the default settings for the pressure outlet of the rotor ( pressure-outlet-rotor).

figure Boundary Conditions figure figure pressure-outlet-rotor figure Edit...

  The Backflow Direction Specification Method was set to Direction Vector when you created the mixing plane, and the Coordinate System to Cylindrical (like for the stator inlet ). The values for the direction cosines are taken from the profiles at the stator.

figure

(a)   Click OK to close the Pressure Outlet dialog box.

6.   Set the conditions for the pressure outlet of the stator ( pressure-outlet-stator).

figure Boundary Conditions figure figure pressure-outlet-stator figure Edit...

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(a)   Retain the default Backflow Direction Specification Method.

  In problems where a backflow exists at the pressure outlet boundary (e.g., torque-converter), you can use this option to specify the direction of the backflow.

(b)   Enable Radial Equilibrium Pressure Distribution.

  Radial equilibrium is used to simulate the pressure distribution which exists due to rotation according to

\frac{\partial p}{ \partial r} = \frac{\rho v_\theta^2}{r}

where $v_\theta$ is the tangential velocity. This is a good approximation for axial flow configurations with relatively straight flow paths (i.e., little change in radius from inlet to exit).

(c)   Select Intensity and Viscosity Ratio from the Specification Method drop-down list.

(d)   Enter 1% for Backflow Turbulent Intensity.

(e)   Enter 1 for Backflow Turbulent Viscosity Ratio.

(f)   Click OK to close the Pressure Outlet dialog box.

7.   Retain the default conditions for the rotor-hub.

figure Boundary Conditions figure figure rotor-hub figure Edit...

  For a rotating reference frame, ANSYS FLUENT assumes by default that walls rotate with the rotating reference frame, and hence are stationary with respect to it. Since the rotor-hub is rotating, you should retain the default settings.

figure

(a)   Click OK to accept the default settings and close the Wall dialog box.

8.   Set the conditions for the inlet hub of the rotor ( rotor-inlet-hub).

figure Boundary Conditions figure figure rotor-inlet-hub figure Edit...

figure

(a)   Select Moving Wall in the Wall Motion list.

  The Wall dialog box will expand to show the wall motion inputs.

(b)   Select Absolute and Rotational in the Motion group box.

(c)   Enter -1 for Z in the Rotation-Axis Direction group box.

(d)   Click OK to close the Wall dialog box.

  These conditions set the rotor-inlet-hub to be a stationary wall in the absolute frame.

9.   Set the conditions for the shroud of the rotor inlet ( rotor-inlet-shroud).

figure Boundary Conditions figure figure rotor-inlet-shroud figure Edit...

figure

(a)   Select Moving Wall in the Wall Motion list.

(b)   Select Absolute and Rotational in the Motion group box.

(c)   Enter -1 for Z in the Rotation-Axis Direction group box.

(d)   Click OK to close the Wall dialog box.

  These conditions will set the rotor-inlet-shroud to be a stationary wall in the absolute frame.

10.   Set the conditions for the rotor shroud ( rotor-shroud).

figure Boundary Conditions figure figure rotor-shroud figure Edit...

figure

(a)   Select Moving Wall in the Wall Motion list.

(b)   Select Absolute and Rotational in the Motion group box.

(c)   Enter -1 for Z in Rotation-Axis Direction group box.

(d)   Click OK to close the Wall dialog box.

  These conditions will set the rotor-shroud to be a stationary wall in the absolute frame.

next up previous contents Previous: Step 6: Cell Zone
Up: Using the Mixing Plane
Next: Step 8: Solution
Release 12.0 © ANSYS, Inc. 2009-02-09