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.