Abstract: The present invention discloses a hub fin device for improving the efficiency of a propeller. The hub fin device can include a propeller having a hub and a plurality of propeller blades that extend radially outward from the hub. Each of the plurality of propeller blades has a trailing edge region. A fin can also be included and located in the trailing edge region of at least one of the plurality of propeller blades. The fin extends radially outward from the hub and reduces or eliminates a hub vortex that is normally present during operation of the propeller.

Abstract: The present invention discloses a hub fin device for improving the efficiency of a propeller. The hub fin device can include a propeller having a hub and a plurality of propeller blades that extend radially outward from the hub. Each of the plurality of propeller blades has a trailing edge region. A fin can also be included and located in the trailing edge region of at least one of the plurality of propeller blades. The fin extends radially outward from the hub and reduces or eliminates a hub vortex that is normally present during operation of the propeller.

Abstract: Apparatus for reducing acoustic radiation which occurs during the operation of turbomachinery includes a shroud having a generally cylindrical inner surface and a coaxial rotor having a plurality of blades extending generally radially outwardly at equally spaced circumferential locations. The inner surface of the shroud is circumferentially contoured such that the tip clearance between each of said blades and the inner surface is caused to vary in a periodic manner upon rotation of said rotor. This creates a new periodic unsteady pressure field which is substantially equal to, and out of phase with, an existing periodic pressure field resulting from nonuniform inflow into the blades and results in the radiation from the turbomachinery of reduced blade rate frequency tones. The inner surface of the shroud may have a circumferential sinusoidal contour whose periodicity is an integral multiple of the number of the blades.

Abstract: Vanes are mounted to an assembly affixed upstream of propeller blades of an utboard motor, creating a counterswirl in the fluid flow to counter the swirl produced by the propeller rotation, enabling on essentially axial discharge jet. The vanes are applied to only a 180 degree sector of the inflow to the propeller.

Abstract: A cyclic-action buoyant toy has no moving parts. The toy floats in water in a first, horizontal position with a port below water level to admit water into a cavity within the toy, while a siphon connected to a drain operates whenever the toy has admitted enough water to assume a second, angled position. The siphon removes water at a faster rate than the port admits water, restoring the toy to the first position, stopping the siphon, and restarting the cyclic action. One embodiment uses a single-ended siphon, while a faster-acting embodiment uses a dual-ended siphon.