Encyclopaedia Index

WORKSHOP - CAD Import: Flow Over Multiple STL Files


The tutorial is a continuation of 'CAD Import: Importing Multiple STL Files'.

In the earlier tutorial, multiple STL files for a complex building geometry were imported. An obvious error in one of the imported file was repaired. In this final stage, the imported STL files are moved to their final positions, the grid is set, boundary conditions are added and a preliminary solution is obtained.

The full geometry of the case is shown in Figure 1 below.


Figure 1. The geometry of the CAD import example

A complete step-by-step guide, showing how to set the case from the default mode of operation, is provided below.

Accessing PHOENICS-VR.

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 with the previous case - click on 'File' then on 'Open existing case', then select CAD\STAGE_2.Q1. If starting this tutorial from scratch, library case 664 can be used instead.


To enter VR Editor:


This is the default mode of operation.

Within VR Editor.

Position the STL files

A plan view of the domain shows this:

The domain is not really big enough, and the buildings are not central enough. Ideally, we want the edges of the domain far enough away from the buildings so that the boundary conditions imposed there do not influence the solution around the buildings.

Resize the domain

Move the buildings


Check and set the grid

Add the boundary conditions

Set Wind profile inlets at left and lower boundaries,  pressure boundaries at the right and upper boundaries, and the friction boundary on the ground plane.

Place the probe

The probe is used to monitor convergence of the solver. It should be placed away from inlets and near outlets.

Set solver parameters

This is a large case, and will take some time to run. The 100 iterations set by default may take around an hour to complete, depending on the speed of the computer. A fully converged run will take 1000-1500 sweeps, and should be considered as an 'overnight' run.

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.

As the Earth solver starts and the flow calculations commence, two graphs should appear on the screen. The left-hand graph shows the variation of solved variables at the monitoring point that was set during the model definition. The right-hand graph shows the variation of errors as the solution progresses.

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, switch the plotting plane to Z (click Z on the handset or toolbar), and 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.

Saving the results.

In the PHOENICS-VR environment, click on 'Save as a case', make a new folder called 'CAD', select the new folder, and save as 'STAGE_3.