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Houlder at World Maritime Technology Conference
Houlder presented two papers at the 2015 Society of Naval Architects and Marine Engineers (SNAME) World Maritime Technology Conference.
Naval Architect. Blanca Peña shared the following with an appreciative audience at the global event.
An investigation into the Motion Behaviour of a wind farm vessel
A number of UK Round Three offshore wind farms are located relatively far from the coast making crew transfer to the sites time consuming, more prone to interruption by weather conditions and increasingly costly. In order to optimize the functionality of a permanent accommodation vessel, Houlder has developed a dedicated Accommodation and Maintenance Wind Farm vessel based on an oil & gas work-over vessel that has been successfully deployed for many years. The Accommodation and Maintenance (A&M) Wind Farm vessel is designed to provide an infield base for Marine Wind Farm operation. The A&M vessel is designed for high operability when it comes to crew access and performance of maintenance and repair of wind turbine components in its workshops. Also general comfort on board is of high regard. As such, the seakeeping behaviour of the unit is of great importance. In this publication, the seakeeping behaviour is presented on the basis of numerical simulations using 3D diffraction software. The first design iteration is driven by achieving high manoeuvrability and good motion characteristics for operational up-time and personnel comfort on board the vessel. Model test data of the original work-over vessel has been used to validate and calibrate the numerical simulations. On this basis, parametric studies can be performed to fine-tune a potential new hull form. In turn, this could reduce the number of required physical model tests providing a potential financial benefit and optimized delivery schedule. The vessel motion behaviour was tested against the acceptability criteria and crew comfort guidelines of motion behaviour for a North Sea environment.
An engineering Approach for Quay-Side Mooring subject to waves
Wave motions from vessels moored in ports open to the sea impact the operability of loading operations, and should be assessed as part of any port (re)development plan. When analysing vessels moored by a quay‐side, time domain simulations may show numeric instabilities resulting in unreliable outcomes. The origin of the numerical instability might lie in the hydrodynamic added mass and wave radiation damping typically calculated using potential flow methods. For certain frequencies, these tend to give negative values. This negative added mass is a known phenomenon in the industry. Combined with negative damping, it is believed to cause instability in non‐linear (coupled) time domain simulations. In these cases, the vessel seems to generate energy rather than dissipate it. As such, the simulations are unlikely to realistically represent real‐life scenarios. This paper describes an engineering method to mitigate numerical instability and derive a working solution to address the operability of loading a vessel subject to wave loading at a quay‐side. The work covers a literature study into negative added mass and damping caused by shallow water and vicinity of objects such as a vertical wall. This is followed by an engineering study using 3D diffraction and time domain software.
Houlder’s papers were included alongside over 200 other innovative and technically advanced papers. The event, in Providence, Rhode Island also featured panel discussions, networking events and an internationally focused exhibition. Now in its fifth year, the World Maritime Technology Conference is fast becoming a key date for the naval architecture and ship design industry.
Contact us if you would like to read either paper or discuss our findings in more detail.
Image courtesy of MaerskLine