A ducted propeller which can be swivelled to give forward, upward, or downward flight to an airship.
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The application of fish hydrodynamics to the silencing of propulsors is considered.
For any single orientation of the laser light sheet, a two-dimensional velocity field can be calculated that describes flow patterns in the vicinity of the propulsor.
A second perspective is that large lateral forces are an unavoidable consequence of undulatory propulsive mechanisms and in fact are expected when a flexible propulsor is oscillated in a fluid.
These results emphasize the importance of examining a range of locomotor behaviors when defining the hydrodynamic repertoire of aquatic animal propulsors.
Submarine engineers eager to copy these features are now experimenting with new kinds of flexible propellers, called propulsors, which resemble the dolphin's tail.
The purpose of this paper is to illustrate how modern tools for visualizing biological fluid flow can provide new insights into the relationship between propulsor structure and hydrodynamic function during aquatic locomotion.
They will be the first of Britain's major Naval vessels to be without traditional rudders, being steered instead by electric-powered propulsors.
For swimming animals, there has been extensive study of the anatomy and kinematics of aquatic propulsors, as well as description of their neuromuscular control.
Most work on unsteady flow during locomotion in fluids has focused on flapping propulsors, and verifications of the theory have necessarily focused on rigid robotic limbs under carefully controlled conditions.
Large lateral forces which could arise as an unavoidable consequence of thrust generation using an undulatory propulsor may also enhance stability and maneuverability.
To achieve this low acoustic signature, the Virginia incorporates newly designed anechoic coatings, isolated deck structures and a new design of propulsor.
With a loud burst, the propulsors emitted a large flame and propelled the Celeste straight into the air.
Swimming in many fish species can be subdivided into a slow swimming gait in which the pectoral fins are the primary propulsors and a fast swimming gait in which the fins are tucked and axial bending generates thrust.
Second, the model can be used for many fast swimmers, although lifting-wing models were developed for the fastest swimming fish with high aspect ratio oscillatory propulsors.
Locomotor forces experienced by aquatic propulsors can be calculated as the reaction to the time rate of change in wake momentum.
To date, the focus of experimental hydrodynamic analyses of fish locomotion has been on the detailed mechanics of propulsor function as reflected in the functional insights presented above.
A third factor contributing to elevated swimming energetic costs, particularly in semi-aquatic mammals, is the efficiency of the propulsor.
Stability depends on hydrodynamic damping and correcting forces, which may be generated by propulsors or by control surfaces moving with the body (trimming).
A conspicuous feature of fish locomotion is the wide diversity of both propulsors and the way these propulsors move and interact with the water to generate propulsive forces.
The propulsors kicked in and the craft was suddenly floating on a large pocket of air.