FLUENT - Flow over an Airfoil- Step 7

Problem Specification
1. Create Geometry in GAMBIT
2. Mesh Geometry in GAMBIT
3. Specify Boundary Types in GAMBIT
4. Set Up Problem in FLUENT
5. Solve!
6. Analyze Results
7. Refine Mesh
Problem 1
Problem 2

Step 7: Refine Mesh

Before we can make any conclusion about the accuracy of our result, we should always make validation check. The most common validation step is grid convergence check.

A finer mesh with four times the original mesh density was created. The lift coefficient was found to be 0.649.

	Original Mesh	Fine Mesh	%Dif
C_L	0.647	0.649	0.3%

We see that the difference is fairly small and concluded that the original mesh is fine enough.

The modeling result obtained is still off from the literature result. Further validation steps are needed before we can conclude about the accuracy of our model. Other parameter that will affect the validity of our result is the choice of viscous model. We used inviscid model which basically assumed that the flow inviscid and totally ignore the effect of boundary layer near the airfoil surface. We might want to try out turbulence model for this high Reynolds number flow.

Summary

Following table shows comparison of modeling result with experimental data.

	C_L	C_d
FLUENT	0.647	0.00249
Experiment	0.6	0.007
% Dif	7.8%	64%

Though further validation steps are still needed before we can come up with a model that will accurately represent the physical flow, this simple tutorial demonstrates the use of reasonable assumption and approximation in obtaining understanding of physical flow properties around an airfoil.

Reference

The experimental data is taken from Theory of Wing Sections By Ira Herbert Abbott, Albert Edward Von Doenhoff pg. 493

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Step 7: Refine Mesh

Summary

Reference