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Step 6: Analyze Results

y+

Turbulent flows are significantly affected by the presence of walls. The k-epsilonturbulence model's validity is grid-independent away from walls but requires verification to make sure it is valid when used near walls. The near-wall model is sensitive to the grid resolution, which is assessed in the wall unit y+, as discussed in Step 4.

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As we can see, the wall _y+_value is between 1.0 and 1.4 (ignoring the anamolous at the inflow). Because these values are less than 5, the near-wall mesh resolution is in the laminar sublayer, which is the most accurate region to which we can resolve the boundary layer.

Save Plot

In the Solution XY Plot Window, check the Write to File box under Options. The Plot button should have changed to the Write... button. Click on Write.... Enter yplus.xy as the filename and click OK. Check that this file has been created in your FLUENT working directory.

Velocity at x = 1m

Main Menu > Plot > XY Plot...

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Select Write to File and save the data for this plot as outflow_profile.xy.

Plot Nusselt Number vs. Reynolds Number

Recall that the Nusselt Number is a non-dimensional heat transfer coefficient that relates convective and conductive heat transfer.

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(click picture for larger image)

Compare Results with Correlation & Experiment

Validate your results form FLUENT by comparing to a correlation and experimental results. The correlation we will use is derived by Reynolds \[1\]:

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