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Verification & Validation

It is very important that you take the time to check the validity of your solution. This section leads you through some of the steps you can take to validate your solution.

Refine Mesh

Let's repeat the solution on a finer mesh with more smaller element size.Repeat the mesh steps, but this time use edge sizing of 50 and 0.02. In the workbench, under Force Convection project, right click on Fluid Flow (FLUENT) and click duplicate. Rename the duplicate project to Force Convection Refined Mesh. You should have two projects cell in workbench.
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Double click on Mesh for Forced Convection Refined Mesh. A new ANSYS Mesher window will open. Under Outline, expand mesh tree and click on Edge Sizing.
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Under Details of "Edge Sizing", enter 60 for Number of Divisions. Under Bias select:

"--- --- - -" and when asked for the bias factor please enter 20.

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Similarly, specify element size of 0.015m for Edge Sizing 2. 
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A bias was used for the vertical edges but not the horizontal edges to keep an optimum y+ value at the wall. This tutorial will not cover y+ values and their meanings, but it may be useful to know for future reference.

Click Update Image Removed to generate the new mesh. If you refer back to the mesh details and expand statistics, you will notice that the number of elements has increased to 19536, compared to 5508 of the original mesh.
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Close the ANSYS Mesher and go back to Workbench windows. Under Forced Convection Refined Mesh, right click on Fluid Flow (FLUENT) and click Update. Wait for a few minutes for FLUENT to obtain a solution.

We would want to compare the solution between the two meshes. To do that, drag the Solution cell of Forced Convection Refined Mesh to Results cell of Forced Convection.
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Finally, double click on Results cell of Forced Convection to compare. Under Outline tab, click on the results of interest to analyze.

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Centerline Pressure

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Let's us look first look at the Pressure drop along the centerline.
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https://confluence.cornell.edu/download/attachments/111221577/Centerline%20Pressure%20Compare.png

Verification Checklist

<iframe width="640" height="360" src="https://www.youtube.com/embed/odNQ8hHG7MA" frameborder="0" allowfullscreen></iframe>

Check Boundary Conditions

 <iframe width="640" height="360" src="https://www.youtube.com/embed/Fzrmdp_cS38" frameborder="0" allowfullscreen></iframe>

Check Mass and Energy Conservation

 <iframe width="640" height="360" src="https://www.youtube.com/embed/0ThDb-tVBQA" frameborder="0" allowfullscreen></iframe>

Check Energy Conservation via Mixed Mean Temperature Variation (Optional)

<iframe width="640" height="360" src="//www.youtube.com/embed/YXkGqLC64-Q" frameborder="0" allowfullscreen></iframe>

Check Numerical Error

 <iframe width="640" height="360" src="https://www.youtube.com/embed/Xmc8fLUX3hc" frameborder="0" allowfullscreen></iframe>

Validation Results

 <iframe width="640" height="360" src="https://www.youtube.com/embed/fkZnLfcbLlc" frameborder="0" allowfullscreen></iframe>

Go to Exercises

The refined mesh pressure correspond better with the experimental data. 
 

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Centerline Temperature

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https://confluence.cornell.edu/download/attachments/111221577/Centerline%20Temperature%20Compare.png

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Wall Temperature

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https://confluence.cornell.edu/download/attachments/111221577/Wall%20Temperature%20Compare.png

 
What can you say about mesh refinement after comparing the results? 

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