Encyclopaedia Index

## Flow Simulation. Step 2.

#### Using the results of step 1.

If you have just completed Step 1 of this tutorial, the Q1 file which you then created should exist as step1.q1 in the sub-directory \phoenics\d_pc\tuts\beginnrs\step1 .

If this does not exist, for whatever reason, use the model file, step1mod.q1, which was provided at installation time in that sub-directory. Then proceed as follows.

#### Starting Step 2.

• In Step 1, only two objects were introduced: and inlet and an outlet.
• The present, Step 2, tutorial shows how to add objects to the computational domain. Specifically, we shall introduce some walls, with the implication then friction is to be considered.
• All other settings are identical to those of the Step 1.
• The geometry is thus shown in the figure below :

PHOENICS allows the effects of walls to be supplied in two different ways, namely:

1. by way of blocks having finite volume and
2. by way of surfaces which have none.
We wil introduce:
• WALL-H - a block of aluminium;
• WALL-L - a second block of aluminium;
• WALL-W - an adiabatic boundary surface, and
• WALL-E - a second adiabatic boundary wall.

### Starting the tutorial

Setting a working directory
1. Activate VR-Editor by the way, described in the previous step.
2. Click on 'Options', then 'Change Working Directory'; check that your working directory is, as before, \phoenics\d_pc\tuts\beginnrs.
3. Otherwise select another working directory.

### Using the Q1 file of the previous step

You will now edit the Q1 file of Step 1 to fit the present requirements. Open it in the VR Editor. To do so:
1. Click on 'File', 'Open existing case'. You will then see the message that 'This operation will wipe out your current settings!' in the 'Open existing case' window. Click on 'OK'.
2. 'Open' window appears with your working ('beginnrs') directory in it.
3. Open 'step1' folder and select the 'case1' Q1 file that you have created in the previous tutorial.

You may as well use the 'model1' Q1 provided during installation.

### In the domain

• Click on 'Menu' and change the title to 'Flow Simulation. Step 2'.
• Click 'OK'.
• It is not necessary to set the domain size, indicate for which variables solution is required and re-size the domain, because you did these already for the existing Q1.

### Introduce and edit the required objects

• Click on the 'object-management' button ('O' on the toolbar or on the Control panel, also sometime called 'hand set').
• This will display the 'object-management' window with a list of objects, containing 'DOMAIN', 'INLET' and 'OUTLET'.
• You will now introduce other objects - walls and make necessary changes in the settings of the existing objects.
1. #### Introduce the WALL-H object

• In the Object-management dialog, click on 'Object', 'New' and New Object'.
• Change name to WALL-H (which stands for 'high wall').
• Click on 'Size' and set SIZE of object as:
• Xsize: 2.0
• Ysize: 1.0
• Zsize: 0.05
• Click on 'Place' and set Position of object as:
• Xpos: 0.0
• Ypos: 0.0
• Zpos: 0.95
• Click on 'General'.
• Select Type: Blockage (default) to set an object of finite thickness.
• To change the material, click on 'Attributes', click on 'Types',
• click on SOLIDS then 'OK', and then on 'ALUMINIUM at 27 deg C' and 'OK'.
• Click on 'OK' to exit the Attributes menu,
• and on 'OK' to close the Object Specification Dialogue Box.
• WALL-H will now appear in the Object-Management list of objects.

2. #### Introduce the WALL-L object

• Click on 'Object', 'New' and 'New Object'.
• Change name to WALL-L (which stands for 'low wall').
• Click on 'Size' and set SIZE of object as:
• Xsize: 2.0
• Ysize: 1.0
• Zsize: 0.05
• Click on 'Place' and leave default Position settings of object as:
• Xpos: 0.0
• Ypos: 0.0
• Zpos: 0.0
• Click on 'General'.
• Define Type: Blockage (default).
• Click on 'Attributes', select material as ALUMINIUM as above.
• Click on 'OK' to return to the Object Specification Dialogue Box, and on 'OK' to close the Object Dialogue Box.

3. #### Introduce the WALL-W object

• Click on 'Object', 'New' and New Object'.
• Change name to WALL-W (which stands for 'west wall').
• Click on 'Size' and set SIZE of object as:
• Xsize: 0.0
• Ysize: 1.0
• Zsize: 0.45
• Click on 'Place' and set Position of object as:
• Xpos: 0.0
• Ypos: 0.0
• Zpos: 0.05
• Click on 'General'.
• Define Type: Plate for an object of infinitesimal thickness.
• Click on 'OK' to close the Object Specification Dialogue Box.

4. #### Introduce the WALL-E object

• Click on 'Object', 'New' and New Object'.
• Change name to WALL-E (which stands for 'east wall').
• Click on 'Size' and set SIZE of object as:
• Xsize: 0.0
• Ysize: 1.0
• Zsize: 0.45
• Click on 'Place' and set Position of object as:
• Xpos: 2.0
• Ypos: 0.0
• Zpos: 0.5
• Click on 'General'.
• Define Type: Plate.
• Click on 'OK' to close the Object Specification Dialogue Box.

5. #### Edit the INLET object

• In the Object Management window double click 'MY_INLET' in the object name list to open the Object Specification window.
• Click on 'Size' and change Zsize to 0.45
• Click on 'Place' and change Zpos to 0.5
• Click 'OK' to close the Object Specification window.

6. #### Edit the OUTLET object

• In the Object Management window double click 'MY_OUT' in the object name list to open the Object Specification window.
• Click on 'Size' and change Zsize to 0.45
• Click on 'Place' and change Zpos to 0.05
• Click 'OK' to close the Object Specification window.

All the required objects are now in the domain and it is possible to close the Object Management window clicking X in the upper right-hand corner.

### Inspect the 'default' grid

Click on the 'Mesh toggle' button. The default mesh (shown as blue and orange lines) will appear on the screen.

• Click anywhere on the image, and the 'Gridmesh settings' dialog box will appear.
• Leave the Number of cells of the previous step, i.e. 20 cells in X, 1 cell in y and 15 cells in Z.
• Click on 'OK' to close the dialog box.
• Click on 'Mesh toggle' again to turn off the mesh display.

### The remaining solution-control parameters

The defaults which have been set in 'Menu', 'Numerics' will suffice for the present purposes.

### Running the Solver

To perform the simulation, click on 'Run', 'Solver'(Earth), and click on 'OK'; to confirm. The solver will be then activated. Upon termination of the calculation, the VR Editor window will be displayed again. Now you can launch the VR Viewer to inspect the results of the calculation.

### Using the VR Viewer.

Click on 'Run', 'Post processor',then GUI Post processor (VR Viewer) . Click 'OK' on the file names dialog to accept the default files.
• Streamlines - click on the 'Streamline management' button
• Iso-surfaces - click on the 'Iso-Surface toggle'

### Saving the results.

• In the VR Viewer click on 'File' then 'Save as a case'. Your working directory \phoenics\d_pc\tuts\beginnrs (the one you have earlier selected) will be displayed.
• Open the 'step2' directory and
• Save there as 'CASE2'.
• Note that the directory contains the Model Q1 file for that case - model2 which you can use when necessary.