Page History

...

...

Main Menu > Solve > Controls > Solution...

Select PISO from the Pressure-Velocity Coupling drop-down list.

Uncheck Skewnes-Neighbor Coupling.

Select Second Order Upwind from the Momentum drop-down list in the Discretization group box. Click OK to close the Solution Controls panel.

Set Initial Guess

Initialize the flow field to the values at the inlet:

...

In the Solution Initialization menu that comes up, choose farfield1 under Compute From. The X Velocity for all cells will be set to 1 m/s, the Y Velocity to 0 m/s and the Gauge Pressure to 0 Pa. These values have been taken from the farfield1 boundary condition.

 
Click Init. This completes the initialization. Close the window.

Patch Region

We will patch the upper region downstream of the flow to create asymmetry so that we can obtain stable oscillation of vortex shedding faster.  

...

Main Menu > Adapt > Region...

 
Enter 1 and 40 for X Min and X Max. Enter 0 and 10 for Y Min and Y Max. Click Mark. FLUENT will print the following message in the console window:
5416 cells marked for refinement, 0 cells marked for coarsening

Close the Region Adaption panel.

We will now patch Y velocity in the registered region.

...

https://confluence.cornell.edu/download/attachments/107011456/patch.jpg 

Select hexahedron-r0 from the Registers to Patch. Select Y Velocity from the Variable selection list. Enter 0.3 for Value. Click Patch.

To check whether you have patch the region, plot contour of velocity in the y direction.

Main Menu > Display > Contours...

Select Velocity... and Y Velocity under Contours of drop-down list. Make sure to check the Filled under Options. Click Display.

https://confluence.cornell.edu/download/attachments/107011456/display_patch.jpg

...

Main Menu > Solve > Monitors > Residual...

Default value for Convergence Criterion for continuity, x-velocity, and y-velocity is 1e-3.

Also, under Options, select Plot and Print. This will plot the residuals in the graphics window as they are calculated.

Click OK.

Monitor also the lift coefficient on the cylinder.

Main Menu > Solve > Monitors > Force...

Under Coefficient, select Lift. Select cylinder under Wall Zones. Under Options, select Print, Plot and Write. Note that Plot Window is 1. Click Apply.

Set Reference Values

The reference values are used to non-dimensionalize the forces and moments action on the wall surface.

Main Menu > Reference Values...

Select  farfield1 from the Compute From drop-down list. FLUENT will update the reference values based on the boundary conditions at farfield1. Change Area to 2. Click OK.

...

Main Menu > Solve > Animate > Define...

 
Increase the Animation Sequences to 1.  Enter 10 for Every. Select Time Step from When drop-down list. Click Define... for sequence-1 to open the Animation Sequence panel.

 
Increase Window to 2 and click the Set button to open a graphics window. Select Contours from the Display Type list to open the Contours panel. Select Velocity... and Vorticity Magnitude from the Contours of drop-down lists.

 
Disable Auto Range and Clip to Range from the Options group box. Enter 0.0001 and 2 for Min and Max, respectively. Select Levels to 50. Click Display. Click OK to close the Animation Sequence panel. Click OK to close the Solution Animation panel. This will save .hmf file after every 10 time steps. We can later create an animation in the form of movie clip using these files. Save the case and data files.
Main Menu > File > Write > Case & Data...

...

The

Strouhal

number

for

flow

past

cylinder

is

roughly

0.183

as

reported

by

Williamson .
In order to capture the shedding correctly, we should have at least 20 to 25 time steps in one shedding cycle. Let's use 25 for our case.

|FLUENT - Unsteady Flow Past a Cylinder - Step 7 #ref1] .
\\
In order to capture the shedding correctly, we should have at least 20 to 25 time steps in one shedding cycle. Let's use 25 for our case.
{latex}
\large
$$
{\rm{Sr}} = {fD \over U} = 0.183
$$
{latex}

For

our

case,

D

=

2,

U

=

1

Therefore,

shedding

frequency

f

=

0.0915

Cycle

time,

{latex}
\large
$$
{\rm{t}} = {1 \over f} = 10.9 sec
$$
{latex}

Therefore,

Time

Step

Size

=

10.9/25

=

0.436

sec

~

0.4

sec

Enter 0.4 for Time Step Size (s). Enter 30 for Max. Iterrations per Time Step. Enter 800 for Number of Time Steps. Click Apply. Click Iterate to start the iterations.

https://confluence.cornell.edu/download/attachments/107011456/Cl%20convergence.jpg

...

Use the default name (Mesh's file name "cylinder") and click OK.

Go to Step 6: Analyze Results

...