Plot of pressure drop decrease

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Note for Mathematica 3 users: The log-log plot labeling problem mare arise here.

We see that increasing q2, the outside fluid flow rate decreases the pressure drop for quite a range.  This is not what is expected for a single fluid flow.  

Just check h so that we are sure it is OK

Note for Mathematica 3 users: This one does not work very well. You need to change the [[5]] to [[1]] to pick out the first root, but some of the values are the wrong root.  

The minimum pressure drop occurs when h ≃ 1.5.  This makes sense because h is supposed to be about 30% of D/2 (= 1.5 for this calculation) for the most efficient flow.