There are many instances where one of the dimensions of an object is considerably smaller than those of the surrounding grid. A typical example is when a thin plate lies at an angle across the grid.
This has always caused problems, so avoiding action has to be taken. One possibility is to use a very fine mesh; another is to artificially increase the thickness of the object so that it can be captured without any gaps or holes.
None of these is entirely satisfactory.
From PHOENICS 2008, there is a possibility to capture thin shapes without having to resort to either of these methods. The idea is to use volume BLOCKAGE objects which can be detected satisfactorily. The blockage is assigned the material 299. This indicates that Earth should perform some special actions:
By arranging that some faces align with the grid, the un-aligned face(s) will be treated as impervious to flow.
This tutorial shows how to use the new technique to create thin partitions of arbitrary shape.
A complete step-by-step guide, showing how to set the case from the default mode of operation, is provided below.
From the system level:
To enter the PHOENICS-VR environment, click on the PHOENICS icon on the desktop, or click on Start, programs, PHOENICS, PHOENICS.
From the commander level:
To enter the PHOENICS-VR environment, click on the 'Run vre' icon in the left column.
In PHOENICS-VR environment,
Start a new case - click on 'File' then on 'Start new case'. Select 'Core' from the list of Special Purpose products and click OK.
To enter VR Editor:
This is the default mode of operation.
Create an 'Angled-plate' blockage
We will now duplicate this object using the array-copy feature, and select different shapes for the copies.
Make the copies
Change the shapes of the copied wedges
Note that we did not have to set the material for the other three shapes, as this was copied from the original wedge.
Set solver parameters
We only need to do a couple of iterations in the solver to see how the shapes have been detected.
Running the solver
To run the PHOENICS solver, Earth, click on 'Run', then 'Solver', then click on 'OK' to confirm running Earth. These actions should result in the PHOENICS Earth monitoring screen.
Viewing the results
Once the Solver run has finished, enter the VR-Viewer to examine the solution (Click 'Run' - 'Post processor' ,'GUI ').
In the Viewer, select the Velocity variable by clicking the icon on the hand-set or toolbar. Switch the contours on by clicking on the hand-set or toolbar.
The blue band of zero velocity follows the shapes of the grid-cutting faces of the objects.
In the PHOENICS-VR environment, click on 'Save as a case', make a new folder called 'ANGLED-PLATE', select the new folder, and save as 'RUN1.
For further examples, try using some of the other geometries in the shapes folder. The half-sphere and quarter-sphere will produce 3D curved surfaces. The grid may have to be adjusted for 3D cases.