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Validation

Blade tip velocity

Torque

Betz's limit

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The blade tip velocity was found to be 98.05 m/s in CFD-Post. This is basically identical to result obtain from hand-calculations which was 98.10 m/s. Great!

Back in the Pre-Analysis section, we had predicted the power coefficient to be around 0.3. As seen on the convergence plot above, the numerical results do agree well with this value considering a sufficient number of elements in the mesh. For example, using a mesh of 2 billion elements, the power coefficient becomes 38% as opposed to the 30% from hand-calculations. These match up quite well considering the many assumptions used in the simple 1D momentum theory. 

At last, we should keep in mind that power coefficient must lie under the Betz limit of 16/27=59.2% for a non-shrouded rotor. Our numerical results correctly fall below this limit. 

Acknowledgments

This tutorial is made under great help and support from:

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