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In the expression tab, create a new expression by right click in the expression window and select "new". Name it Wall shear.

In Details of Wall shear, right below the Expressions window, enter the following and click on Apply. The value for the wall shear stress will be displayed.

probe(Wall Shear)@wall point

We will now define the dynamic pressure. Create another expression and name it Dynamic pressure. In Details of Dynamic pressure, enter the following and click on Apply.

0.5*13*(1m/s)^2

It is important to enter the appropriate units so the dynamic pressure has the correct unit. Recall both the density and the upstream velocity are set to 1.

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The skin friction coefficient is the wall shear stress divided by the dynamic pressure. Create another expression and name it Cf. Enter the following and click on Apply.

Wall shear/Dynamic pressure

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The skin friction coefficient is a dimensionless parameter. The value is 0.129533 at the point (0,0,0).

Go to Step 7: Verification & Validation

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