But in any case (5) is a reliable estimate for the minimum possible drag on a rigid body of revolution.
In the previous section it has been shown that the boundary layer around a slender body of revolution can be reduced to that on a plate with the use of the Mangler-Stepanov transformation.
Since for laminar attached flow on a slender body of revolution [C.sub.V] is independent of the shape (see (5)), the hull shape maybe arbitrary provided it ensures a laminar attached flow.
The profile NACA-66 was chosen for the shape of this body of revolution; its parameters were L/D = 3.33; D = 0.48 m; L = 1.6 m; V = 0.159 [m.sup.3].
The volumetric drag coefficient of an ideal laminar unseparated body of revolution with a prescribed volume is independent of the shape and can be calculated from expression (5), which can be a rather good estimate of the drag on the best-shaped fish.
The BNSS utilizing the relationship of viscous and pressure force on blunt
body of revolution, through sacrifice small viscous force, early flow separation on the blunt
body of revolution was restrained, and pressure force can be reduced dramatically, so the total force reduced also.