Step 7: Boundary Conditions

Boundary Conditions

  For this problem, you need to set the boundary conditions for all boundaries.

  

1.   Set the boundary conditions for the lower velocity inlet ( v_uniform) for the primary phase.

Boundary Conditions v_uniform

  For the Eulerian multiphase model, you will specify conditions at a velocity inlet that are specific to the primary and secondary phases.

(a)   Select air from the Phase drop-down list.

(b)   Click the Edit... button to open the Velocity Inlet dialog box.

i.   Retain the default selection of Magnitude, Normal to Boundary from the Velocity Specification Method drop-down list.

ii.   Enter 0.25 m/s for the Velocity Magnitude.

iii.   Click the Thermal tab and enter 293 K for Temperature.

iv.   Click OK to close the Velocity Inlet dialog box.

2.   Set the boundary conditions for the lower velocity inlet ( v_uniform) for the secondary phase.

Boundary Conditions v_uniform

(a)   Select solids from the Phase drop-down list.

(b)   Click the Edit... button to open the Velocity Inlet dialog box.

i.   Retain the default Velocity Specification Method and Reference Frame.

ii.   Retain the default value of 0 m/s for the Velocity Magnitude.

iii.   Click the Thermal tab and enter 293 K for Temperature.

iv.   Click the Multiphase tab and retain the default value of 0 for Volume Fraction.

v.   Click OK to close the Velocity Inlet dialog box.

3.   Set the boundary conditions for the orifice velocity inlet ( v_jet) for the primary phase.

Boundary Conditions v_jet

(a)   Select air from the Phase drop-down list.

(b)   Click the Edit... button to open the Velocity Inlet dialog box.

i.   Retain the default Velocity Specification Method and Reference Frame.

ii.   Enter 0.25 m/s for the Velocity Magnitude.

  In order for a comparison with analytical results [1] to be meaningful, in this simulation you will use a uniform value for the air velocity equal to the minimum fluidization velocity at both inlets on the bottom of the bed.

iii.   Click the Thermal tab and enter 293 K for Temperature.

iv.   Click OK to close the Velocity Inlet dialog box.

4.   Set the boundary conditions for the orifice velocity inlet ( v_jet) for the secondary phase.

Boundary Conditions v_jet

(a)   Select solids from the Phase drop-down list.

(b)   Click the Edit... button to open the Velocity Inlet dialog box.

i.   Retain the default Velocity Specification Method and Reference Frame.

ii.   Retain the default value of 0 m/s for the Velocity Magnitude.

iii.   Click the Thermal tab and enter 293 K for Temperature.

iv.   Click the Multiphase tab and retain the default value of 0 for the Volume Fraction.

v.   Click OK to close the Velocity Inlet dialog box.

5.   Set the boundary conditions for the pressure outlet ( poutlet) for the mixture phase.

Boundary Conditions poutlet

  For the Eulerian granular model, you will specify conditions at a pressure outlet for the mixture and for both phases.

  The thermal conditions at the pressure outlet will be used only if flow enters the domain through this boundary. You can set them equal to the inlet values, as no flow reversal is expected at the pressure outlet. In general, however, it is important to set reasonable values for these downstream scalar values, in case flow reversal occurs at some point during the calculation.

(a)   Select mixture from the Phase drop-down list.

(b)   Click the Edit... button to open the Pressure Outlet dialog box.

i.   Retain the default value of 0 Pascal for Gauge Pressure.

ii.   Click OK to close the Pressure Outlet dialog box.

6.   Set the boundary conditions for the pressure outlet ( poutlet) for the primary phase.

Boundary Conditions poutlet

(a)   Select air from the Phase drop-down list.

(b)   Click the Edit... button to open the Pressure Outlet dialog box.

i.   Click the Thermal tab and enter 293 K for Backflow Total Temperature.

ii.   Click OK to close the Pressure Outlet dialog box.

7.   Set the boundary conditions for the pressure outlet ( poutlet) for the secondary phase.

Boundary Conditions poutlet

(a)   Select solids from the Phase drop-down list.

(b)   Click the Edit... button to open the Pressure Outlet dialog box.

i.   Click the Thermal tab and enter 293 K for the Backflow Total Temperature.

ii.   Click the Multiphase tab and retain default settings.

iii.   Click OK to close the Pressure Outlet dialog box.

8.   Set the boundary conditions for the heated wall ( wall_hot) for the mixture.

Boundary Conditions wall_hot

  For the heated wall, you will set thermal conditions for the mixture, and momentum conditions (zero shear) for both phases.

(a)   Select mixture from the Phase drop-down list.

(b)   Click the Edit... button to open the Wall dialog box.

i.   Click the Thermal tab.

a.   Select Temperature from the Thermal Conditions list.

b.   Enter 373 K for Temperature.

ii.   Click OK to close the Wall dialog box.

9.   Set the boundary conditions for the heated wall ( wall_hot) for the primary phase.

Boundary Conditions wall_hot

(a)   Select air from the Phase drop-down list.

(b)   Click the Edit... button to open the Wall dialog box.

i.   Select Specified Shear from the Shear Condition list.

  The Wall dialog box will expand.

ii.   Retain the default value of 0 for X-Component and Y-Component.

iii.   Click OK to close the Wall dialog box.

10.   Set the boundary conditions for the heated wall ( wall_hot) for the secondary phase same as that of the primary phase.

Boundary Conditions wall_hot

  For the secondary phase, you will set the same conditions of zero shear as for the primary phase.

11.   Set the boundary conditions for the adiabatic wall ( wall_ins) for the primary phase.

Boundary Conditions wall_ins

  For the adiabatic wall, you will retain the default thermal conditions for the mixture (zero heat flux), and set momentum conditions (zero shear) for both phases.

(a)   Select air from the Phase drop-down list.

(b)   Click the Edit... button to open the Wall dialog box.

i.   Select Specified Shear from the Shear Condition list.

  The Wall dialog box will expand.

ii.   Retain the default value of 0 for X-Component and Y-Component.

iii.   Click OK to close the Wall dialog box.

12.   Set the boundary conditions for the adiabatic wall ( wall_ins) for the secondary phase same as that of the primary phase.

Boundary Conditions wall_ins

  For the secondary phase, you will set the same conditions of zero shear as for the primary phase.