Special-shaped low-drag laminar hulls to increase speed and improve the commercial efficiency of floating vehicles

Slender bodies of revolution with an attached boundary layer can delay its turbulization and ensure low pressure drag. That is why studying of the unseparated rigid bodies, similar in contours to aquatic animals, allowed the conclusion that the shape itself can provide low drag inherent in laminar flow. The volumetric friction drag coefficient of elongated axisymmetric unseparated hulls reaches its minimum at the critical Reynolds number, which relates their speed, volume, and length with the kinematic viscosity of the fluid and can be used for optimization in unbounded flows of water or air. The characteristics of proposed hulls moving on the water surface are still unknown. Nevertheless, it was shown that special shapes with very sharp concave noses, similar to the fastest fish rostrums, allow the removal of stagnation points and high pressures on the body surface. This effect allows for reducing the wave resistance. The potential attached flow of inviscid incompressible fluid around a slender body of revolution moving horizontally at constant speed near the water surface was simulated with the use of sources and sinks located on the axis of symmetry and sources and sinks with opposite intensity located on a corresponding line above the water surface. The absence of the pressure peaks and low values of the vertical component of velocities on the water surface were demonstrated for specially shaped bodies of revolution with sharp concave noses for different elongations and depths of movements. For comparison, the same characteristics were calculated for shapes with convex noses. The total drag, commercial efficiency, and maximal displacement of the laminar hull were estimated. Low values of drag yield rather high speeds of movement with the use of standard engines. After corresponding testing, the proposed shapes can be used to reduce the total drag of ships and rowing racing shells and to increase the speed and commercial efficiency.