Computer Study to Establish the Lower Limit of Length-to-Diameter Ratio Advisable for Low-Drag Bodies

摘要

A computer study was conducted to establish theoretically the lowest advisable ratio of length to diameter for a 30-inch-diameter body moving at 45 knots, submerged in the ocean, at zero angle of attack. If the boundary layer is turbulent over the entire body, it appears inadvisable to decrease the l/d much below the DOLPHIN I value of 3.33. If laminar flow extends to the minimum pressure point at 58 percent of the length, an l/d of 2.62 may be permitted. There is a good theoretical basis for expecting laminar flow to extend to the minimum pressure point with l/d = 2.62. The drag of a fin-stabilized, 30-inch-diameter body of l/d = 2.62 at 45 knots could be as low as 375 pounds compared to 550 pounds for a body with l/d = 3.33. (Author)