This disclosure relates to a system for reducing cavitation at a surface that moves relatively with respect to a first fluid. The system comprises a degasser configured to at least partially degas a second fluid. The system also comprises a reservoir in communication with the degasser and configured to house the at least partially degassed second fluid, the reservoir having an outlet that is arranged for directing the second fluid towards the surface. The system is configured such that the directing of the at least partially degassed second fluid towards the surface forms a boundary layer at the surface. The boundary layer is adapted to at least partially increase the negative pressure required to initiate cavitation at the surface so as to reduce the occurrence of cavitation during such relative movement.

This disclosure relates to a system for reducing cavitation at a surface that moves relatively with respect to a first fluid. The system comprises a degasser configured to at least partially degas a second fluid. The system also comprises a reservoir in communication with the degasser and configured to house the at least partially degassed second fluid, the reservoir having an outlet that is arranged for directing the second fluid towards the surface. The system is configured such that the directing of the at least partially degassed second fluid towards the surface forms a boundary layer at the surface. The boundary layer is adapted to at least partially increase the negative pressure required to initiate cavitation at the surface so as to reduce the occurrence of cavitation during such relative movement.

The present invention relates to a method for protecting surfaces of components against cavitation erosion and components provided with such cavitation protection surfaces, wherein in the surface a plurality of microcavities is provided which entrap gas such as air; the gas, air, entrapped inside the microcavities expands in the vicinity of cavitation bubbles, forming a gas cushion layer that directs cavitation jets away from the surface, thereby protecting the surface against cavitation erosion; the cavitation having a reentrant or double reentrant inlet design with typical T-shape and T-shape profile

The present invention relates to a method for protecting surfaces of components against cavitation erosion and components provided with such cavitation protection surfaces, wherein in the surface a plurality of microcavities is provided which entrap gas such as air; the gas, air, entrapped inside the microcavities expands in the vicinity of cavitation bubbles, forming a gas cushion layer that directs cavitation jets away from the surface, thereby protecting the surface against cavitation erosion; the cavitation having a reentrant or double reentrant inlet design with typical T-shape and T-shape profile

According to the present disclosure there is provided an arrangement for influencing fluid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface, the vortex generator surface comprising a series of laterally aligned projections, to induce vortices in the liquid flow.

According to the present disclosure there is provided an arrangement for influencing fluid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface, the vortex generator surface comprising a series of laterally aligned projections, to induce vortices in the liquid flow.

The present invention relates to a cavitation free rotary mechanical device with improved output and, in particular, to a rotary mechanical device (such as a hydro turbine, marine propeller, etc) including a rotatable shaft and associated blades (or cups or vanes), the rotary mechanical device configured to introduce air at one or more areas of extremely low pressure force on the surface of, or at least in the proximity of, the rotatable blades (or cups or vanes) during rotation and thereby prevent cavitation effects that would otherwise be caused by the extremely low pressure forces acting on such surfaces during operation.

A propeller shield to selectively shield rotating blades of a propeller. The propeller shield may include a shield element for placement adjacent to the propeller blades. The shield element may include multiple gates configured to open in response to water flow generated by the propeller. The gates may be configured to open away from the propeller in response to a forward movement of the boat, and to close towards the propeller in response to cessation of the forward movement.

A propeller shield to selectively shield rotating blades of a propeller. The propeller shield may include a shield element for placement adjacent to the propeller blades. The shield element may include multiple gates configured to open in response to water flow generated by the propeller. The gates may be configured to open away from the propeller in response to a forward movement of the boat, and to close towards the propeller in response to cessation of the forward movement.

A method is for making a marine drive for propelling a marine vessel in water. The method includes providing a gearcase; installing a propeller shaft assembly that extends forwardly from the gearcase; coupling front and rear propellers to the propeller shaft assembly, forwardly of the gearcase, such that rotation of the propeller shaft assembly causes rotation of the front and rear propellers, respectively, which thereby propels the marine vessel in the water; and reducing deleterious effects of cavitation on the gearcase by the combination of forming the gearcase with a wide trailing end portion, in particular to maintain pressure alongside the gearcase, and configuring the front and rear propellers so that the front propeller absorbs more torque/thrust load than the rear propeller during said rotation.