Abstract: A full-scale resistance prediction for ships. More particularly, the invention is directed to full-scale resistance predictions for ships using model scale resistance tests. This process involves the designing of a momentum thickness similarity simulator for a model, to accurately determine a model resistance and ultimately to predict a ship resistance. The simulator modifies the geometry of the model, and its design is optimized to accurately predict the ship resistance. The simulator may be an external device such as a wire ring (trip wire), sand paper, or a Hama strip, or the simulator may be integrally formed on the body of the model.

Abstract: Exemplary practice of the present invention provides and implements a superior small-scale test model of a full-scale vessel hull describing a smooth axisymmetric body. The boundary layer of a smooth axisymmetric body moving in water is characterized, in succession from front axial-longitudinal end to back axial-longitudinal end, by a laminar region, an unstable region, an intermittent region, and a turbulent region. The smooth axisymmetric body's intermittent region is characterized by generation of turbulent spots, which bring about the turbulent region. According to exemplary inventive practice, a “turbulent spot inducer” (ring-shaped structure or structural arrangement) is strategically sized and placed to increase generation of turbulent spots, thereby reducing (axially-longitudinally shortening) the intermittent region and enlarging (axially-longitudinally lengthening) the turbulent region.

Abstract: A bilge keel design for improved ship roll damping performance. The bilge keel has a porous region substantially at a forward end, and is designed to alleviate and mitigate added drag from flow misalignment due to scale effects and variation in vessel speed and loading conditions. The bilge keel design is use on both port and starboard sides of the vessel hull.

Abstract: The invention is directed to an apparatus for mitigating the load impact on a surface watercraft and passengers therein, during high speed travel. The hull includes a damping cavity for mitigating the load impact on the surface watercraft. The damping cavity is positioned on a dry portion of an undersurface of the hull between a forward end and an aft end of the hull. The damping cavity includes a porous plate on the undersurface, and a deck plate within the hull body. The deck plate and the porous plate are separated by a gap, and an inflatable bladder may be positioned in the gap between the plates.

Abstract: A method and apparatus is directed towards an advanced blade section for propellers that allow watercrafts to effectively travel in both sub-cavitating and super-cavitating modes. The advanced blade section includes a streamlined profile having a convex upper surface and a lower surface that includes both a convex portion and a concave portion. When the propellers are rotated in a first direction at low speeds to propel the watercraft in the forward direction, the advanced blade section experiences a fully wetted flow over both the upper and lower surfaces at low speeds. At high speeds, the advanced blade section experiences a partially wetted flow, with only a front part of the lower surface being fully wetted, at high speeds. When the propellers are rotated in a second direction opposite the first direction to reduce the speed of the watercraft, the blade section experiences a substantially wetted flow over both upper and lower surfaces.

Abstract: A high-speed water vessel including a steering arrangement for reducing cavitation and its effects. The arrangement includes a twisted rudder pair located downstream of a high-speed propulsor. The rudder pair may also be contoured at a bottom portion thereof. The propulsor has at least one propeller having a propeller diameter. In operation, the propulsor produces a slipstream that contracts with distance from the propeller. To avoid the effects of cavitation, the twisted rudder pair is positioned outside and adjacent to the slipstream diameter, with the rudders of the rudder pair separated by a distance that is less than the diameter of the propellers. The rudders of the rudder pair may be in a substantially parallel orientation with respect to each other. In gas turbine applications, the rudder pairs may be rotated towards each other to produce a rudder bucket for producing a negative thrust for stopping the high-speed water vessel.

Abstract: The stern hull portion of a surface ship or underwater sea craft is provided with a waterjet propulsion unit having an outlet end from which a discharge propelling waterjet emerges underwater and undergoes flow beyond the stern end of the hull between a pair of twin contoured rudders normally positioned for straight forward propulsion of the hull. The contoured rudders pivotally mounted underwater on the hull are angularly displaced by maneuvering control in opposite directions from the normal positions to maneuvering positions with their lower end tips in contact with each other to form a bucket to directionally change flow of the emerging waterjet for steering, deceleration and backing purposes during hull propulsion between low and high speeds. The twin rudders are also angularly displaced by the maneuvering control in the same angular direction for a different directionally regulated change in waterjet flow to effect turning of the hull for propulsion in a reverse direction.

Abstract: The hull of a submerged sea craft adjacent its stern end is provided with auxiliary facilities for controlled maneuvering operations under low speed conditions, including steering, stopping and negative thrust backing performed independently of main propulsion of the craft. The auxiliary maneuvering control facilities include a curved channel pipe connected to two angularly related sub-channel pipe sections for selectively controlled outflow of fluid which is pressurized by a maneuvering control pump within the curved channel pipe before outflow through exit openings in the hull in different directions, as negative angle thrust jets and as steering control jets perpendicular to the hull centerline. By use of a sub-channel flow diverting flapper and gate valves at the inlet and exit outlet openings in the hull, all of the maneuvering operations may be performed under selective control.

Abstract: Forward underwater movement of a sea craft at a high speed induced by propulsion thereof is decelerated and stopped by projection of drag devices, mounted on a fully submerged underwater sea craft hull, from retracted positions within said sea craft hull or the steering rudders positioned thereon. Each of the drag devices has an elongated drag plate with an end surface cap flush with the outer surface of the hull or the steering rudder in the retracted position of the drag device.

Abstract: The stern hull portion of a sea craft through which main exit flow channels extend to projecting jet propulsion nozzles, is provided with facilities for controlled maneuvering of the sea craft, including steering, stopping, negative thrust backing and docking without substantial hydrodynamic loading and with facilitated installation. Such maneuvering control facilities include a secondary flow channel extending from each of the main exit flow channels having two angularly related subchannel branches for pressurized water outflow through gated openings in the hull from which propulsion jets emerge under maneuvering control. Either control of a subchannel diverting flapper, or by use of selective closure gates and a flow diverting flap within the main exit flow channel, maneuvering may be effected in response to inflow through inlet openings in the hull of water that is pressurized before supply to the main exit flow channels.

Abstract: Corrective stabilizing motions are applied to a sea vessel hull during seawater travel in response to stern flap displacement by hydrodynamic forces induced at the buttock of the vessel hull and by the lower flap surfaces at the stern end of the sea vessel hull in response to angular displacement of flap elements from a deployed position in either in-phase or out-of-phase relation to each other in rough seas. An angle of attack range for limiting angular displacement of the flaps is selected so as to minimize resistance to travel and optimize fuel saving during propulsion of the vessel hull at different speeds under different seawater conditions.

Abstract: Spaced cambered wedges having flow diverting surfaces thereon are deployed from retracted positions within the smooth surfaced sides of a marine vessel hull undergoing water travel above a high speed, under which air ventilated cavities are established by the deployed wedges along the sides of the hull, imposing drag on the hull sides of a substantially reduced magnitude as compared to that otherwise imposed directly by the water alone.

Abstract: Depressors mounted on the stern of a marine vessel are deployed by displacement from positions retracted from the seawater to positions immersed therein so as to divert exit flow of the seawater along retarded flow paths from the stern during vessel travel. Such deployment of the depressors is regulated under motion stabilizing control to produce corrective roll and pitch inducing forces on the vessel in response to diversions of the exit flow by the depressors.

Abstract: A skidplate projecting into a body of water from a marine craft hull has a symmetric wedge formation extending from the leading edge to differently profiled surfaces on opposite sides of the skidplate producing lift and side force during travel. No side force is however produced during straight line travel by virtue of ventilated cavity enclosure of the profiled surfaces on both sides between cavity establishing streamlines extending through the water from the symmetric wedge formation.

Abstract: The inventive apparatus exercises control of the water flow which is discharged from a marine waterjet propulsor. Typical inventive embodiments comprise plural horizontal and plural vertical blade-like structures which together describe an open-ended, box-like rectilinear configuration characterized by at least two adjacent channels. Every vertical blade-like structure includes, at its aft end, a “steering” flap which is pivotable about a vertical axis. Some inventive embodiments advance marine craft reversing by implementing one or more bucket-like devices behind the inventive apparatus.

Abstract: Cavitation of a hydrofoil element, such as the rudder of a marine vessel, om exposure to a body of water during onset flow at different angles to the chordal axis of the rudder profile, is suppressed by a tab on the lower end tip of the rudder. Such tab has external surfaces thereon which affect flow separation relative to the rudder so as to suppress or delay cavitation.

Abstract: A hydrofoil structures for efficient operation over a wide speed range from subcavitating to supercavitating operation is provided. The dualcavitating hydrofoil overcomes cavitation problems associated with high speed operation of prior art subcavitating hydrofoils by providing a supercavitating profile shape in the lower surface to achieve a supercavitating condition at high speeds, and overcomes performance related problems associated with low speed operation and structural problems associated with high speed operation of prior art supercavitating hydrofoils by providing a profile shape having a robust trailing edge that employs the Coanda effect to achieve a smooth flow exit at the trailing edge. The dualcavitating hydrofoil includes upper and lower surfaces defining a profile that includes a tapered section adjacent to and extending aft from the leading edge and a thick curved section adjacent to and extending forward of the trailing edge.

Abstract: The invention is directed to hydrofoil structures for efficient operation over a wide speed range from subcavitating to supercavitating operation. A dualcavitating hydrofoil is provided that overcomes cavitation problems associated with high speed operation of prior art subcavitating hydrofoil structures by providing a supercavitating profile shape in the lower surface to achieve a supercavitating condition at high speeds, and that overcomes problems associated with low speed operation of prior art supercavitating hydrofoil structures by providing an upper surface that combines with the lower surface to form a streamlined cross-sectional shape that achieves a smooth flow exit at the trailing edge for efficient, low drag, high lift subcavitating operation.

Abstract: Ship rudders are subjected to propeller induced velocities and induced flow ngles that vary along the rudder span and chord. Because of non-zero onset flow angles, a suction pressure peak is formed at or near the leading edge of the rudder where early cavitation occurs. The present invention is directed to a rudder and method for minimizing early cavitation and related ship vibration and for thus improving acoustic and hydrodynamic performance thereof. The rudder of the present invention is twisted so as to have profiles along its entire span that are aligned with propeller induced non-zero onset flow angles into the rudder. The twist of the rudder sections vary in the spanwise direction, that is, the twist angle of one rudder sections may vary relative to the twist angle of adjacent or remaining rudder sections, such that the rudder experiences substantially zero angles of attack along the span from the rudder's root to the rudder's tip.

Abstract: Ship rudders are subjected to propeller induced velocities and induced flow angles that vary along the rudder span and chord. Because of non-zero onset flow angles, a suction pressure peak is formed at or near the leading edge of the rudder where early cavitation occurs. The present invention is directed to a rudder and method for minimizing early cavitation and related ship vibration and for thus improving acoustic and hydrodynamic performance thereof. The rudder of the present invention is twisted so as to have profiles along its entire span that are aligned with propeller induced non-zero onset flow angles into the rudder plane. The twist of the rudder sections vary in the spanwise direction, that is, the twist angle of one rudder sections may vary relative to the twist angle of adjacent or remaining rudder sections, such that the rudder experiences substantially zero angles of attack along the span.