Physics Setup

In the Workbench window, this is what you should see currently in the Project Schematic space.

Double click on Setup which will bring up the FLUENT Launcher. When the FLUENT Launcher appears change the options to "Double Precision", and then click OK as shown below.The Double Precision option is used to select the double-precision solver. In the double-precision solver, each floating point number is represented using 64 bits in contrast to the single-precision solver which uses 32 bits. The extra bits increase not only the precision, but also the range of magnitudes that can be represented. The downside of using double precision is that it requires more memory. 

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Click OK to select the default options in the FLUENT Launcher. Twiddle your thumbs a bit while the FLUENT interface comes up. This is where we'll specify the governing equations and boundary conditions for our boundary-value problem. On the left-hand side of the FLUENT interface, we see various items listed under Problem Setup. We will work from top to bottom of the Problem Setup items to setup the physics of our boundary-value problem. On the right hand side, we have the Graphics pane and, below that, the Command pane.

Display Mesh

 Let's first display the mesh that was created in the previous step. 

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Click Edit... to set up the correct inlet parameters. The Velocity Inlet window pops up. Enter 30.06 next to Velocity Magnitude (m/s). Under Turbulence, select the specification method to be K Intensity and Epsilon. For Turbulent Kinetic Energy (m2/s2), enter value 0.09. For Turbulent Dissipation Rate (m2/s3), enter value 16. Note that k and epsilon are not measured and are rough guess values. The Viscosity Ratio. Use the default values for Turbulent Intensity (5%) and Turbulent Viscosity Ratio (10). These are plausible guess values for the turbulence level at the inlet. FLUENT will calculate k and epsilon at the inlet from these values and use them as boundary conditions for the k and epsilon equations.  The results should not be sensitive to these inputs since most of the turbulence is generated in the boundary layers (ideally, you should check the sensitivity of your calculation to this setting). 

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 Now click on Thermal tab and enter 298.15K for Temperature. Click OK to close the window.
 
Finally, set up the outlet boundary condition:
Boundary Conditions > Outlet
FLUENT selects the pressure-outlet boundary type and its guess turns out to be right. 

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Now FLUENT knows all necessary elements of our beloved BVP (domain, governing equations and boundary conditions). In the Solution step, we'll prod the beast to obtain an approximate numerical solution to our BVP.

Go to Step 5: Numerical Solution

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