Bhattacharyya coefficient

Complete information on the importance of a single feature i for the separation of classes is shown by class-conditional probability density curves (Figure 46). A small overlap of both curves indicates a high discrimination power of that feature. The overlap may be measured by the common area, by the Bhattacharyya coefficient, by the transinformation, or some other criteria (Chapter 11.6 and 11.7). 

The Bhattacharyya coefficient B is a measure of the overlap of two density functions. 

For Re 300000 the resistance crisis occurs. The drag force depends on wake dimensions and these dimensions also depend upon the position of the separation line between the wake and the boundary layer. As Re increases, the turbulent separation point moves back as a consequence the wake dimensions diminish and the drag coefficient drops sharply from 0.4 to 0.1 (Fig. 20). All of these considerations are reported in detail by Torobin and Gauvin Boulos, Bhattacharyya and... 

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