FLAIR Tutorial 8: Flow over Big Ben

This is a 3D simulation of the flow over Big Ben. The case is to show how to import the STL of the Big Ben into the FLAIR VR-Editor. The size of the Big Ben used in the simulation is 6m long, 6m wide and 30m high whereas the size of the calculation domain is set to 100m long, 100m wide and 50m high as shown in the picture below. This tutorial is also shows how to use a Wind_profile Object to describe the wind profile at the upstream boundary.

Setting up the model

Start FLAIR with the default mode of operation

The FLAIR VR-Environment screen should appear, which shows the default domain with the dimensions 10mx10mx3m.

Resizing the domain

Adding the object to the calculation domain

a. add Big Ben

The geometry of the Big Ben object is available in an STL file. The following steps show how to use the 'Object management' dialog box to import the STL file.

X: 40.0 m

Y: 40.0 m

Z: 0.0 m

X:6.0 m

Y:6.0 m

Z:30.0 m

b. create the inlet boundary with a wind profile

In order to create a wind profile, we use a User-defined object combined with the In-Form facility.

X:100. m

Y:100. m

Z: 0. m

X: 0.0 m

Y: 0.0 m

Z: 0.0 m

c. add the sky

X:100.0 m

Y:100.0 m

Z:0.0 m

X: 0.0 m

Y: 0.0 m

Z: 50.0 m

d. add the downstream boundary

X: 0.0 m

Y: 100. m

Z: 50. m

X: 100. m

Y: 0.0 m

Z: 0.0 m

e. add the ground

X:100. m

Y:100. m

Z:0. m

X: 0.0 m

Y: 0.0 m

Z: 0.0 m

c. add the side boundaries

X:100. m

Y:0. m

Z:50. m

X: 0.0 m

Y: 0.0 m

Z: 0.0 m

X: 0.0 m

Y: 100.0 m

Z: 0.0 m

To activate the physical models

a. The Main Menu panel

 

b. To activate K-E turbulence model

c. To set the grid numbers and to solver parameters

in X-direction to 50 cells

in Y-direction to 50 cells

in Z-direction to 24 cells

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.

To the end of the calculation, the monitoring display would be as shown below.

Viewing the results

Saving the case

Once a case has been completed, it can be saved to disk as a new Q1 file by 'File - Save working files'. The Q1 and associated output files can be saved more permanently by 'File - Save as a case'.