A system and a method for reducing drag on the aft-fuselage of an aircraft are provided, which system and method utilize at least one (inlet provided on each side of the aft-fuselage of an aircraft for reducing drag -on the aft-fuselage, which finlets are (i) positioned at the rear half of an upswept portion of the aft-fuselage starting at a breakline, (ii) positioned in the path of the vortices generated by the aft-fuselage, and (iii) oriented at 1 to 9 degrees angle relative to the local airflow about the aft-fuselage of the aircraft to straighten the airflow about the aft-fuselage. In addition, the finlets generate an induced secondary vortex having an opposite rotation direction relative to the rotation direction of the vortices generated by the aft-fuselage, thereby counteracting the vortices generated by the aft-fuselage.

A rowing oar is described. The rowing oar can have a plurality of flow disrupters arranged on a shaft of the oar. In one embodiment, the flow disrupters can be circular bumps arranged in lines along the shaft of the oar. The flow disrupters can cause the air flow over the oar to be more turbulent so that the flow separation on a backside of the oar is reduced. The reduction in flow separation can reduce aerodynamic drag on the oar when it travels through the air. Thus, a rower can expend less energy during rowing using the oar.

The present invention relates to a bullet with an increased effective range. The bullet includes a front end portion (10) having a hemispherical shape, a recess portion (20) connected to a rear end of the front end portion (10) and having a curved surface that is recessed inward, an inclined portion (30) connected to a rear end of the recess portion (20) and inclined at a predetermined angle (A) with respect to a horizontal line, a stepped portion (40) connected to a rear end of the inclined portion (30) and inclined at a predetermined angle (A) with respect to the horizontal line, and fluid inducing grooves formed from the rear to a rear end surface of the bullet (1). Thus, when the bullet passes through underwater, super cavitation may be more effectively generated and maintained for even longer to significantly increase the effective range of the bullet.

A fluid control film is provided that includes fluid control channels extending along a channel longitudinal axis. Each of the fluid control channels has a surface and is configured to allow capillary movement of liquid in the channels. The fluid control film further includes a hydrophilic surface treatment covalently bonded to at least a portion of the surface of the fluid control channels. The fluid control film exhibits a capillary rise percent recovery of at least ten percent. Typically, the hydrophilic surface treatment includes functional groups selected from a non-zwitterionic sulfonate, a non-zwitterionic carboxylate, a zwitterionic sulfonate, a zwitterionic carboxylate, a zwitterionic phosphate, a zwitterionic phosphonic acid, and/or a zwitterionic phosphonate. A process for forming a fluid control film is also provided. Further, a process for cleaning a structured surface is provided, including providing a structured surface and a hydrophilic surface treatment covalently bonded to at least a portion of the structured surface, and soiling the structured surface with a material. The process also includes removing the material by at least one of submerging the structured surface in an aqueous fluid, rinsing the structured surface with an aqueous fluid, condensing an aqueous fluid on the structure surface, or wiping the structured surface with a cleaning implement.

Airfoil and hydrofoils systems with structures having a surface texture defined by fractal geometries are described. Raised portions or fractal bumps can be included on the surfaces, forming a surface texture. The surface textures can be defined by two-dimensional fractal shapes, partial two-dimensional fractal shapes, non-contiguous fractal shapes, three-dimensional fractal objects, and partial three-dimensional fractal objects. The surfaces can include indents having fractal geometries. The indents can have varying depths and can be bordered by other indents, or bumps, or smooth portions of the airfoil or hydrofoil structure. The fractal surface textures can reduce vortices inherent from airfoil and hydrofoil structures. The roughness and distribution of the fractal surface textures reduce the vortices, improving laminar flow characteristics and at the same time reducing drag. The systems are passive and do not require applied power.

Described herein are a viscous drag reduction apparatus and a method. The apparatus includes a pair of rollers connected to a supporting surface on a roof of the vehicle, a belt having a frictional surface and partially wrapped around the pair of rollers, such that the pair of rollers allow the belt to rotate in response to an air flow generated around the vehicle when the vehicle is in motion, the pair of rollers having a length in an axial direction that is at least as long as a width of the belt, an assembly of the pair of rollers and the belt being at least partially recessed with respect to a top line of the roof, and a reverse flow cover connected to the front end of the roof of the vehicle to block an air back flow generated by the belt when rotating.

A fairing for suppressing a vortex induced vibration (VIV) of a tubular including an encircling member dimensioned to encircle a tubular, the encircling member having a first side that extends toward a second side when the encircling member is positioned around a tubular. The fairing further including a support member positioned between the first side and the second side, the support member having a channel formed therein, and an opening to the channel is positioned between the first side and the second side. In addition, the fairing includes a tail member positioned within the channel, the tail member having a substantially planar surface that extends radially outward from the channel.

Body provided with a superficial area adapted to reduce drag when the body is moving relative to a gaseous or watery medium, comprising depressions in said superficial area, wherein the depressions have a greater length than width and are provided in the superficial area so as to collectively shape a curvature provided in a length direction of said depressions in the superficial area, and/or said depressions themselves are provided with a curvature in their length direction. The depressions are thus adapted to provide that a turbulent boundary layer of the gaseous or watery medium adjacent to the superficial area of the body is exposed to lateral excitation with reference to a movement direction of the body in the gaseous or watery medium or with reference to a flow direction of said turbulent boundary layer along said superficial area of the body. Said lateral excitation results in a reduction of drag.

A coating apparatus for the reduction of aerodynamic noise and vibrations. The coating apparatus is configured to include a group of fibrillar structures, wherein each fibrillar structure is configured with a diverging tip so that the coating reduces the size of and shifts downstream, a separation bubble, and modulates large-scale recirculating motion. Each fibrillar structure can be configured as a cylindrical micropillar. The group of fibrillar structures can be configured as a group of uniformly distributed cylindrical micropillars (e.g., one or more micropillar arrays). The surface coating is effective in reducing the separation bubble and displacing the separation bubble downstream. The coating facilitates a reduction in noise (e.g., aerodynamic noise) and vibrations due to the reduction in the size of the separation bubble.

Described herein are a viscous drag reduction apparatus and a method. The apparatus includes a pair of rollers connected to a supporting surface on a roof of the vehicle, a belt having a frictional surface and partially wrapped around the pair of rollers, such that the pair of rollers allow the belt to rotate in response to an air flow generated around the vehicle when the vehicle is in motion, the pair of rollers having a length in an axial direction that is at least as long as a width of the belt, an assembly of the pair of rollers and the belt being at least partially recessed with respect to a top line of the roof, and a reverse flow cover connected to the front end of the roof of the vehicle to block an air back flow generated by the belt when rotating.