Speed and position control systems for marine vehicles have been subject to an increased focus with respect to performance and safety. An example is represented by drilling operations performed with semi submersible rigs where the control of position and heading requires high accuracy. Drifting from the well position could cause severe damage to equipment and environment. Also, the use of under...

Kilometer-sized moonlets in Saturn’s A ring create S-shaped wakes called “propellers” in surrounding material. The Cassini spacecraft has tracked the motions of propellers for several years and finds that they deviate from Keplerian orbits having constant semimajor axes. The inferred orbital migration is known to switch sign. We show using a statistical test that the time series of orbital long...

We present an apparatus that generates statistically homogeneous and isotropic turbulence with a mean flow that is less than 10% of the fluctuating velocity in a volume of the size of the integral length scale. The apparatus is shaped as an icosahedron where at each of the 12 vertices the flow is driven by independently controlled propellers. By adjusting the driving of the different propellers...

in this work, a numerical study of sheet cavitation has been performed on dtmb4119 marine propellers, using boundary element method (based on potential flow assumption). in propeller design, various parameters of geometry and flow are incorporated. so, a computer program is needed to take all parameters into account and solve the flow. capability of analyzing the wetted and cavitating flow arou...

In this paper a recently reported four-quadrant nonlinear thrust controller for marine propellers is applied to the velocity control of an underwater vehicle. The controller, designed for fixed pitch electrically driven propellers, is based on a shaft speed control and employs an estimate of the propeller torque loss. A simulation study is performed in order to compare the presented approach wi...

This paper numerically discusses how the performance of a NACA marine propeller is affected by the number of blades, which is one of the most crucial geometrical parameters determining the performance of a propeller. Results are presented in terms of the hydrodynamic and structural parameters. The results show that changing the number of blades changes the hydrodynamic efficiency, torque, thrus...

Speed and position control systems for marine vehicles have been subject to an increased focus with respect to performance and safety. An example is represented by drilling operations performed with semi submersible rigs where the control of position and heading requires high accuracy. Drifting from the well position could cause severe damage to equipment and environment. Also, the use of under...

This paper presents a relaxed definition of hover for multicopters with propellers pointing in a common direction. These solutions are found by requiring that the multicopter remain substantially in one position, and that the solutions be constant when expressed in a coordinate system attached to the vehicle. The vehicle’s angular velocity is then shown to be either zero or parallel to gravity....

Abstract This paper presents a method for modeling ducted fan propulsion systems hybrid-electrically driven small aircraft based on mean line flow analysis methods. Studies of the essential design parameters provide basis discussion potential advantages when compared to free propellers, as well possible new fields application fan. A two-seater aircraft, equipped with two fans powered by combust...