DESIGN OF LOW-DRAG AUTONOMOUS UNDERWATER VEHICLES AND FLOW CONTROL

Design of autonomous underwater vehicles (AUV) met the opposite challenges. Their achievable route can be enhanced with drag reduction due to an increase of AUV slenderness. However, blunt short AUV have others operational advantages. The possibility to design low-drag bodies for Reynolds numbers employed by contemporary AUV (2X10(6)<Re<10(7)) is based on a combination of known facts. First, blunt bodies experience a drag crisis associated with laminar-turbulent transition in their boundary layers and some boundary layer suction additionally reduces their drag. Second, the transition can be delayed till much higher Re for bodies without adverse pressure gradients over their forward and medium parts. Suction on sterns of such bodies allows for the very substantial drag reduction. Several body shapes with distributed suction with extremely low slenderness (L/B<1.5) are presented. Their drag coefficients are between 0.007 and 0.02, whereas for ellipsoid of the same slenderness it exceeds 0.08.