A spoiling apparatus for triggering a turbulent transition by autonomous disturbance and spoilers. The spoilers are mounted in multiple grooves in the circumferential direction of a navigating body, when a flow autonomously undergoes a turbulent transition, the spoilers remain in the grooves, the surface of the navigating body is free of protrusion, thus causing no additional flow resistance. A rated critical Reynolds number is set, in a case of a reduced flow speed and reduced density, the flow is a laminar flow, at which time the pressure applied to the spoilers by the flow is reduced, and the spoilers are ejected under the effect of compression springs. When ejected, the spoilers disturb the flowing of the bottom layer of the flow, and trigger the laminar flow into a turbulent flow. By setting the rebounding force of the compression springs, the spoiling apparatus is turned on automatically when a disturbance-triggered turbulent transition is required and is turned off when not required, thus implementing the autonomous control of turbulent transitions.

A ground effect craft having a ground effect wing, a plurality of sponsons, and a control system is disclosed. The ground effect wing may include a fore ground effect wing and an aft ground effect wing. The ground effect wing may generate a stabilizing moment on at least one sponson to stabilize the ground effect craft. The plurality of sponsons may be dynamically coupled to the body. The plurality of sponsons may be dynamically coupled to each other. The dynamic coupling may permit the sponsons to move relatively independent of the body and each other, thereby stabilizing the ground effect craft. The ground effect craft may include a stabilizing wing.

An apparatus including a controllable fluid-contacting surface is provided. In another aspect, the present apparatus includes a flexible membrane and multiple actuators each having an output shaft or activation member coupled to a water-contacting membrane, with the shafts extending in a direction offset from the nominal outer surface of the membrane. A further aspect of the present apparatus includes an underwater vessel including a propulsion source, a flexible membrane having a water-contacting outer surface and an electronic controller including programmable software for actuating the actuators.

Provided is a filtering apparatus configured to interact with objects of interest within a medium. The properties of the filtering apparatus can be configured to modify the trajectory of individual objects of interest which interact with the filtering apparatus within several orders of magnitude of the mean free path of objects of interest. Surfaces of a filtering apparatus can be constructed to preferentially redirect objects of interest in a desired direction, such as a direction substantially parallel to a surface, or substantially along the length of a channel connecting two reservoirs. This can modify the net diffusion of objects of interest relative to the surface, which can modify the bulk fluid flow velocity magnitude along the surface. This can be employed to reduce the viscous drag on a surface moving relative to a fluid, or to generate thrust, or to convert thermal energy of a fluid into useful work.

A cover device for at least partially closing an underwater opening in a hull of a watercraft includes a variable-volume hollow-chamber lip assembly including at least two hollow-chamber lips and one buoyancy body. The at least one hollow-chamber lip is volume-variable by supplying a fluid to or removing a fluid from an interior thereof, and the at least one hollow-chamber lip assembly is shiftable between an expanded state and a contracted state by supplying or removing the fluid.

A ground effect craft having a ground effect wing, a plurality of sponsons, and a control system is disclosed. The ground effect wing may include a fore ground effect wing and an aft ground effect wing. The ground effect wing may generate a stabilizing moment on at least one sponson to stabilize the ground effect craft. The plurality of sponsons may be dynamically coupled to the body. The plurality of sponsons may be dynamically coupled to each other. The dynamic coupling may permit the sponsons to move relatively independent of the body and each other, thereby stabilizing the ground effect craft. The ground effect craft may include a stabilizing wing.

A generally cylindrical element 10 that is adapted for immersion in water is described. The generally cylindrical element 10 has an outer surface 11 that is in contact with the water in use. The outer surface 11 has at least two rows of repeating shapes 20, for example hexagons 20, provided on the surface 11, where each row of repeating shapes 20 is separated from the other or the adjacent row(s) by a groove arrangement 30. Each shape 20 within a row is separated from the, or each, adjacent shape 20 by at least one groove 30. This configuration of the surface 11 reduces Vortex Induced Vibration (VIV) and/or drag that may act upon the generally cylindrical element 10 when it is immersed in a body of water.

A generally cylindrical element 10 that is adapted for immersion in water is described. The generally cylindrical element 10 has an outer surface 11 that is in contact with the water in use. The outer surface 11 has at least two rows of repeating shapes 20, for example hexagons 20, provided on the surface 11, where each row of repeating shapes 20 is separated from the other or the adjacent row(s) by a groove arrangement 30. Each shape 20 within a row is separated from the, or each, adjacent shape 20 by at least one groove 30. This configuration of the surface 11 reduces Vortex Induced Vibration (VIV) and/or drag that may act upon the generally cylindrical element 10 when it is immersed in a body of water.

An irregular surface texture fabricated on a body which travels through fluid in order to reduce the flow drag incurred by the body moving relative to the fluid. The dominate orientation of the irregular surface texture runs in the longitudinal direction, however, ridge and valley structures may occur in any orientation so that the resulting texture mimic the turbulence characteristic present in the surrounding flow field.

An irregular surface texture fabricated on a body which travels through fluid in order to reduce the flow drag incurred by the body moving relative to the fluid. The dominate orientation of the irregular surface texture runs in the longitudinal direction, however, ridge and valley structures may occur in any orientation so that the resulting texture mimic the turbulence characteristic present in the surrounding flow field.