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Step 7: Verification & Validation
Verification and validation is a formal process for checking results. Each of these terms has a specific meaning which we won't get into here. We'll act like high-priced consultants and do the bare minimum: we'll refine the mesh and make sure that the results are nearly independent of the mesh.
Note to Cornell MAE 4272 Students:
Comparison with the experimental measurements is another way you'll check the FLUENT results.
Refine Mesh
Let's repeat the solution on a finer mesh with smaller cells. In workbench, under Forced Convection project, right click on Fluid Flow (FLUENT) and click duplicate. Rename the duplicate project to Force Convection Refined Mesh. You should have two project cells in workbench.
Double click on Mesh for Forced Convection Refined Mesh. The ANSYS Mesher window will open. Under Outline, expand mesh tree and click on Edge Sizing.
Highlight "Edge Sizing". Under Details of "Edge Sizing", increase Number of Divisions to 50. This will refine the mesh in the radial direction.
Highlight "Edge Sizing 2". Under Details of "Edge Sizing 2", decrease Element Size to be 0.02. This will refine the mesh in the axial direction.
Click Update 
to generate the new mesh. If you highlight Mesh in the tree and expand Statistics, you will notice that the number of elements has increased to about 12,800, compared to 5508 of the original mesh.
Close the ANSYS Mesher and go back to Workbench window. 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 on the new mesh and update all the results.
We would want to compare the solution on the two meshes. To do that, drag the Solution cell of Forced Convection Refined Mesh to Results cell of Forced Convection.
Finally, double click on Results cell of Forced Convection to compare the results on the two meshes. Select the Chart Viewer tab near the bottom of the graphics window. Double-click on Centerline Temperature in the Tree view to see the updated results (pretty sweet, huh?).
The red line corresponds to the refined mesh. Similarly, one can check wall temperature variation on the two meshes.
Refining the mesh doesn't change the wall temperature much but the centerline temperature changes a fair bit. So another level of mesh refinement would be wise.