Blossom Heath Harbor/USCG Station St. Clair Shores Harbor Entrance Study

http://deepblue.lib.umich.edu/bitstream/2027.42/96628/1/39015087358381.pd

OMAE2002-28536 COUPLED DYNAMIC ANALYSIS OF A MINI TLP: COMPARISON WITH MEASUREMENTS

ABSTRACT A numerical code (COUPLE) was recently developed for computing 6 Degree-Of-Freedom (DOF) motions of a moored floating structure dynamically interacting with its mooring/riser/tendon system. The computation of hydrodynamic forces on the moored structure can be conducted based on a diffraction wave theory model, e.g. WAMIT, and/or the Morison Equation based upon a slender body assumption. Wave kinematics up to the free surface, used in the Morison Equation, is computed using nonlinear deterministic Hybrid Wave Models, and is accurate up to second order in wave steepness. Experimental data from the model tests of a mini TLP was used as the basis for investigation of the numerical computation. Using COUPLE and its alternatives, coupled as well as quasi-static analyses were conducted for the mini TLP model that incorporates four risers and four tendons. Two different methods for computing hydrodynamic loads, namely, WAMIT and Morison Equation, were used, respectively. Through the comparison between the numerical results and the corresponding measurements, dynamic interactions between the riser/tendon system and the hull were examined. Findings made in this study, though based upon a mini TLP may have valuable applications to the design and simulation of a wide range of compliant deep-water structures

Proceedings of WMU Maritime Week 2024 Beyond Horizons: Maritime Sustainability

This proceedings is the output of the WMU Maritime Week 2024 Conference, which was held from August 27 to 30, 2024, at WMU in Malmö. As the first conference of WMU Maritime Week, it focused on themes such as the IMO World Maritime Day theme 2024: \u27Navigating the Future: Safety First!\u27, Maritime Sustainability, Digitalization, Decarbonization, Maritime Business and Logistics, and Capacity Development. A total of 42 experts in these fields presented across 8 sessions. This proceeding provides a summary of the presentations from all the speakers.https://commons.wmu.se/wmu_mw24/1000/thumbnail.jp

Control of an open-loop hydraulic offshore wind turbine using a variable-area orifice

The research work disclosed in this publication is partly funded by the Malta Government Scholarship Scheme.The viability of offshore wind turbines is presently affected by a number of technical issues pertaining to the gearbox and power electronic components. Current work is considering the possibility of replacing the generator, gearbox and electrical transmission with a hydraulic system. Efficiency of the hydraulic transmission is around 90% for the selected geometries, which is comparable to the 94% expected for conventional wind turbines. A rotor-driven pump pressurises seawater that is transmitted across a large pipeline to a centralised generator platform. Hydroelectric energy conversion takes place in Pelton turbine. However, unlike conventional hydro-energy plants, the head available at the nozzle entry is highly unsteady. Adequate active control at the nozzle is therefore crucial in maintaining a fixed line pressure and an optimum Pelton turbine operation at synchronous speed. This paper presents a novel control scheme that is based on the combination of proportional feedback control and feed forward compensation on a variable area nozzle. Transient domain simulation results are presented for a Pelton wheel supplied by sea water from an offshore wind turbine-driven pump across a 10 km pipeline.peer-reviewe

TIME-DOMAIN SIMULATION OF RISER VIV IN SHEARED CURRENT

ABSTRACT Riser vortex-induced vibrations (VIV) have attracted significant attentions in recent years in offshore oil and gas industry. There is an increasing interest in using computational fluid dynamics (CFD) approach for deepwater riser VIV timedomain simulations. Our previous study has demonstrated that the long riser (L/D=1400) VIV response in uniform current can be predicted with reasonable accuracy by time domain simulations with Chimera over-set data grid technique. This paper is to further that study and investigate the riser VIV in sheared current profiles. The riser studied in this paper is a long marine riser with constant tension distribution. Its prototype has an outer diameter (OD) of 0.027m and a mass ratio of 1.6. The fluid domain is discretised using approximately one million elements. A linearly sheared current is imposed in perpendicular to the riser, and the flow field is calculated using an unsteady Reynolds-Averaged Navier-Stokes (RANS) numerical method in conjunction with a Chimera domain decomposition approach with overset grids. The critical parameters including riser VIV root-mean-square (rms) a/D, vorticity, drag and lift coefficients are processed, and compared to those of uniform current and experimental data. The simulation results show that the riser VIV under sheared current behaves differently from uniform current. It is also shown that the presented CFD approach provides reasonable results and is suitable for long riser VIV evaluation in deepwater and complex current conditions