Current Search: Stability of ships (x)
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- Title
- A direct thrust measurement system for a waterjet propelled, free running USV.
- Creator
- Grimes, John A., von Ellenrieder, Karl, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The relationship between cross-flow at a waterjet inlet and delivered thrust is not fully understood. A direct thrust measurement system was designed for a waterjet propelled, free running USV. To induce sway velocity at the waterjet inlet, which was considered equivalent to the cross flow, circles of varying radii were performed at Reynolds Numbers between 3.48 x 106 and 8.7 x 106 and radii from 2.7 to 6.3 boat lengths. Sway velocities were less than twenty percent of mean forward speed with...
Show moreThe relationship between cross-flow at a waterjet inlet and delivered thrust is not fully understood. A direct thrust measurement system was designed for a waterjet propelled, free running USV. To induce sway velocity at the waterjet inlet, which was considered equivalent to the cross flow, circles of varying radii were performed at Reynolds Numbers between 3.48 x 106 and 8.7 x 106 and radii from 2.7 to 6.3 boat lengths. Sway velocities were less than twenty percent of mean forward speed with slip angles that were less than 20°. Thrust Loading Coefficients were compared to sway as a percent of forward speed. In small radius turns, no relationship was seen, while in larger radius turns, peaks of sway velocity corresponded with drops in thrust, but this was determined to be caused by reduced vehicle yaw in these intervals . Decoupling of thrust and yaw rate is recommended for future research.
Show less - Date Issued
- 2013
- PURL
- http://purl.flvc.org/fau/fd/FA0004023
- Subject Headings
- Oceanographic instruments -- Evaluation, Propellers, Ship propulsion, Ships -- Hydrodynamics, Stability of ships
- Format
- Document (PDF)
- Title
- Determination of Hydrodynamic Coefficients of Multi-Hull Ships for Seakeeping Analysis.
- Creator
- Chafin, Jesse Ryan, Ananthakrishnan, Palaniswamy, Florida Atlantic University
- Abstract/Description
-
Linear and non-linear hydrodynamic coefficients of single and multiple hulls are obtained using the boundary-integral method. For linear frequency-domain analysis, the boundary-integral method based on a simple source distribution (Yeung [50] was used. The nonlinear time domain simulations were carried out using a boundary-integral algorithm based on the mixed Eulerian-Lagrangian (MEL) formulation (Longuet-Higgins and Cokelet (19] ). Also, linear time domain simulations were carried out by...
Show moreLinear and non-linear hydrodynamic coefficients of single and multiple hulls are obtained using the boundary-integral method. For linear frequency-domain analysis, the boundary-integral method based on a simple source distribution (Yeung [50] was used. The nonlinear time domain simulations were carried out using a boundary-integral algorithm based on the mixed Eulerian-Lagrangian (MEL) formulation (Longuet-Higgins and Cokelet (19] ). Also, linear time domain simulations were carried out by utilizing a simplified mixed Eulerian-Lagrangian formulation and the steady-state results compared with that obtained from linear-frequency domain analysis. Both 2D and 3D results were obtained for a range of parameters such as beam/draft, hull-separation/beam ratios and frequency and amplitude of hull motions. The results shed light on complex wave-body interactions involved in multi-hull ships and identifY critical hydrodynamic and geometric parameters affecting their sea keeping performance. The computational tools developed and the findings thus contribute to design of multi-hull ships for improved atsea performance.
Show less - Date Issued
- 2007
- PURL
- http://purl.flvc.org/fau/fd/FA00012511
- Subject Headings
- Ships--Seakeeping--Mathematical models, Stability of ships, Ships--Hydrodynamics
- Format
- Document (PDF)
- Title
- Development and implementation of an adaptive controller for station keeping of small outboard-powered vessels.
- Creator
- Fisher, Aaron D., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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In this thesis multiple controllers are developed which command a small boat with twin tied outboard motors to hold a desired position. In the process of developing a controller to hold a position, controllers were first developed which follow a desired heading or path over ground with the motors outputting constant thrust. These heading and path following controllers were tuned and tested in a numerical simulation, then validated on the R/V Lee and Ocean Power vessels through sea trials in...
Show moreIn this thesis multiple controllers are developed which command a small boat with twin tied outboard motors to hold a desired position. In the process of developing a controller to hold a position, controllers were first developed which follow a desired heading or path over ground with the motors outputting constant thrust. These heading and path following controllers were tuned and tested in a numerical simulation, then validated on the R/V Lee and Ocean Power vessels through sea trials in the Atlantic Ocean. After successful path following trials were performed, station keeping algorithms were developed and tuned in the numerical simulation, now with heading and thrust of the vessel both being variables to be controlled. After tuning in the numerical simulation, the Ocean power vessel was outfitted with systems for controlling throttle and steering with sea trials conducted in the Atlantic Ocean for station keeping.
Show less - Date Issued
- 2010
- PURL
- http://purl.flvc.org/FAU/2975247
- Subject Headings
- Ship handling, Stability of ships, Fracture mechanics, Boats and boating, Design, PID controllers, Computer simulation
- Format
- Document (PDF)
- Title
- Investigation of marine waterjet inlets during turning maneuvers.
- Creator
- Duerr, Phillip S., von Ellenrieder, Karl, Florida Atlantic University, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Numerical simulations of waterjet inlets have been conducted in order to understand inlet performance during ship turning maneuvers. During turning maneuvers waterjet systems may experience low efficiency, cavitation, vibration, and noise. This study found that during turns less energy arrived at the waterjet pump relative to operating straight ahead, and that the flow field at the entrance of the waterjet pump exhibited a region of both low pressure and low axial velocity. The primary reason...
Show moreNumerical simulations of waterjet inlets have been conducted in order to understand inlet performance during ship turning maneuvers. During turning maneuvers waterjet systems may experience low efficiency, cavitation, vibration, and noise. This study found that during turns less energy arrived at the waterjet pump relative to operating straight ahead, and that the flow field at the entrance of the waterjet pump exhibited a region of both low pressure and low axial velocity. The primary reason for the change in pump inflow uniformity is due to a streamwise vortex. In oblique inflow the hull boundary layer separates when entering the inlet and wraps up forming the streamwise vortex. These changes in pump inflow during turning maneuvers will result in increased unsteady loading of the pump rotor and early onset of pump rotor cavitation.
Show less - Date Issued
- 2015
- PURL
- http://purl.flvc.org/fau/fd/FA00004364, http://purl.flvc.org/fau/fd/FA00004364
- Subject Headings
- Fluid dynamics, Ships--Hydrodynamics, Ships--Maneuverability--Simulation methods, Ship handling--Simulation methods, Ship propulsion, Stability of ships, Oceanographic instruments--Evaluation
- Format
- Document (PDF)