According to the present disclosure there is provided a duct arrangement for influencing fluid flow, the duct arrangement comprising: a duct section arranged to receive a fluid flow therethrough, the duct section defining a first direction through the duct section from a fluid inlet end to a fluid outlet end; a rotor housed in the duct section, the rotor comprising one or more rotor blades; and a vortex generator surface housed in the duct section, the vortex generator surface arranged to induce vortices in the fluid flow through the duct section.

Disclosed is a method of decreasing pressure fluctuation induced on a surface of a hull due to propeller cavitation by using real-time vibration information and adjusting rotation angles of two propellers of a twin-propeller ship.

A marine drive has an internal combustion engine that rotates a propulsor shaft that is operatively coupled to a propulsor to impart a propulsive thrust in water. The marine drive has a gearcase housing having an upper portion above a lower portion, the lower portion supporting the propulsor shaft. An exhaust passage in the gearcase housing is configured to convey exhaust gas from the internal combustion engine. An exhaust outlet on the upper portion of the gearcase housing is configured to discharge the exhaust gas from the exhaust passage to the water. The exhaust outlet faces the propulsor so that the exhaust gas is discharged into the water and towards the propulsor so as to aerate the water encountered by the propulsor.

A marine drive has an internal combustion engine that rotates a propulsor shaft that is operatively coupled to a propulsor to impart a propulsive thrust in water. The marine drive has a gearcase housing having an upper portion above a lower portion, the lower portion supporting the propulsor shaft. An exhaust passage in the gearcase housing is configured to convey exhaust gas from the internal combustion engine. An exhaust outlet on the upper portion of the gearcase housing is configured to discharge the exhaust gas from the exhaust passage to the water. The exhaust outlet faces the propulsor so that the exhaust gas is discharged into the water and towards the propulsor so as to aerate the water encountered by the propulsor.

Disclosed is a method of decreasing pressure fluctuation induced on a surface of a hull due to propeller cavitation by adjusting a relative rotation angle of propellers of a twin-propeller ship.

Disclosed is a method of decreasing pressure fluctuation induced on a surface of a hull due to propeller cavitation by using real-time vibration information and adjusting rotation angles of two propellers of a twin-propeller ship.

A diffuser-type endplate propeller driving a hull and including a propeller hub a plurality of blades is provided. The propeller hub has an axis of rotation and is connected to a transmission shaft of the hull. The blade has a blade-body and an endplate. The blade-body is connected to the propeller hub and extends outward from the propeller hub to the corresponding endplate, the endplate bends from the corresponding blade-body to extend towards a stern of the hull, and the endplate has a leading edge and a trailing edge. A cylindrical surface is imaginarily formed by the leading edges while the diffuser-type endplate propeller is rotated about the axis. Each of the endplates has a first tangent plane at the leading edge thereof, the cylindrical surface has a second tangent plane at the leading edge. An included angle is measured from the second tangent plane to the first tangent plane.

A marine drive has an internal combustion engine that rotates a propulsor shaft that is operatively coupled to a propulsor to impart a propulsive thrust in water. The marine drive has a gearcase housing having an upper portion above a lower portion, the lower portion supporting the propulsor shaft. An exhaust passage in the gearcase housing is configured to convey exhaust gas from the internal combustion engine. An exhaust outlet on the upper portion of the gearcase housing is configured to discharge the exhaust gas from the exhaust passage to the water. The exhaust outlet faces the propulsor so that the exhaust gas is discharged into the water and towards the propulsor so as to aerate the water encountered by the propulsor.

A marine drive has an internal combustion engine that rotates a propulsor shaft that is operatively coupled to a propulsor to impart a propulsive thrust in water. The marine drive has a gearcase housing having an upper portion above a lower portion, the lower portion supporting the propulsor shaft. An exhaust passage in the gearcase housing is configured to convey exhaust gas from the internal combustion engine. An exhaust outlet on the upper portion of the gearcase housing is configured to discharge the exhaust gas from the exhaust passage to the water. The exhaust outlet faces the propulsor so that the exhaust gas is discharged into the water and towards the propulsor so as to aerate the water encountered by the propulsor.

A marine vessel comprising: at least one buoyant tubular foil; and at least one baffle plate positioned about the perimeter of the at least one buoyant tubular foil so as to protrude into the flow of water passing by the perimeter of the at least one buoyant tubular foil, whereby to create a high-pressure zone fore of the at least one baffle plate and a low-pressure zone immediately aft of the at least one baffle plate, whereby to create a dense stream of supercavitated water immediately aft of the at least one baffle plate.