Smart materials application on high performance sailing yachts for energy harvesting

Piezoelectric patches are bounded on a keel bulb in order to harvest vibration energy by converting electrical output. Unsteady computational fluid dynamics method is also used to find the structural boundary condition such as the hydrodynamic pressure fluctuation. Finite element analysis (FEM) is used to find structural and electrical responses

Numerical study of asymmetric keel hydrodynamic performance through advanced CFD

The hydrodynamics of an asymmetric IACC yacht keel at angle of yaw are presented using simulations performed by advanced computational fluid dynamics using state-of-the-art software. The aim of the paper is to continue working on the improvement of numerical viscous flow predictions for high-performance yachts using Large Eddy Simulation and Detached Eddy Simulation on unstructured grids. Quantitative comparisons of global forces acting on the keel and wake survey are carried out. Qualitative comparisons include flow visualisation, unsteady and separated flow and other features. Star-CCM+ and the trimmed cell method give better forces and wake prediction compared to the unstructured mesh of ANSYS Fluent. Both solvers give good flow visualisation near and far field of the keel

Systematic cavitation tunnel tests of a propeller in uniform and inclined flow conditions as part of a round robin test campaign

The effect of shaft inclination can induce important unsteady hydrodynamic phenomenon usually associated with small and high-speed craft. This paper presents systematic cavitation tunnel tests with a 214 mm diameter model propeller of a catamaran research vessel. The propeller is subjected to uniform and inclined flow conditions, to investigate its efficiency, cavitation and underwater radiated noise characteristics. The experiments were conducted in the Emerson Cavitation Tunnel of Newcastle Uni- versity based on the starboard 5-bladed right-hand propeller of the University's research vessel, The Princess Royal. In the paper the details of the tests and significant findings for the effect of the shaft inclination on the propeller efficiency, cavitation and underwater radiated noise characteristics are presented. A better understanding is sought in relation to the noise signatures of different types of cavitation. The systematic tests presented in the paper also have a long-term objective, being the first of an organised round robin test campaign that is being currently undertaken by the members of the Underwater Noise Community of Practice (CoP) of Hydro-Testing Forum (HTF). This long-term objective is to repeat similar tests in the different facilities of all CoP members to reveal the relative merits of their testing facilities for underwater noise investigations

Numerical optimization and experimental validation for a tidal turbine blade with leading-edge tubercles

Recently the leading-edge tubercles on the pectoral fins of humpback whales have attracted the attention of researchers who wish to exploit this feature in the design of turbine blades to improve the blade performance. The main objective of this paper is therefore to make a further investigation into this biomimetic design inspiration through a fundamental research study involving a hydrofoil section, which represents a straightened tidal turbine blade, with and without the leading-edge tubercles, using computational and experimental methods. Firstly a computational study was conducted to optimise the design of the leading-edge tubercles by using commercial CFD code, ANSYS-CFX. Based on this study the optimum tubercle configuration for a tidal turbine blade with S814 foil cross-section was obtained and investigated further. A 3D hydrofoil model, which represented a "straightened" tidal turbine blade, was manufactured and tested in the Emerson Cavitation Tunnel of Newcastle University to investigate the effect of various tubercle options on the lift and drag characteristics of the hydrofoil. The experiments involved taking force measurements using a 3-component balance device and flow visualisation using a Particle Image Velocimetry (PIV) system. These tests revealed that the leading-edge tubercles may have significant benefits on the hydrodynamic performance of the hydrofoil in terms of an improved lift-to-drag ratio performance as well as reducing the tip vortex which is main cause of the undesirable end-effect of 3D foils. The study explores further potential benefits of the application of leading-edge tubercles on tidal turbine blades

What to expect from the hydrodynamic energy saving devices

Many retrofitting technologies have been proposed to improve the hydrodynamic performance of existing fleets with the aim of reducing the fuel consumption and consequently CO2 emission. The magnitudes of savings predicted by manufacturers are very promising however ship owners are often still doubtful whether they can achieve what is claimed in operations. This study evaluates the performance of four energy saving devices (ESDs) at ship scale with the aim of assisting ship owners with the decision of selecting suitable devices for their ships. Due to the uncertainties associated with extrapolation of viscous flows from model to full scale it is proposed that investigations must be carried out at full scale; hence a full-scale com putational model was adopted as the only feasible method at the design stage. Two vessels representing di fferent types of ship were selected: a gas carrier and a container ship. Various retrofitting technologies to reduce resistance or to improve the propulsive efficiency were considered. The latter group is subdivided into devices located before, at and aft of the propeller. The resistance induced by large openings on the hull, such as a bow thruster tunnel was quantified and several devices designed to streamline the flow in this region were evaluated. Pre-swirl fins technology was the ESD investigated from preswirl devices. The existing propeller of the gas carrier was replaced with a new type profile propeller which improved the propulsive efficiency. Twisted rudder was the technology investigated from post-swirl ESDs. The level of savings obtained from these technologies was generally less than the values published in the literature. It was concluded that this discrepancy arose for one of three reasons: either the metric used to evaluate the savings was inappropriate, or that the method used to quantify the measure was in accurate, or finally, because the designs examined in the case studies were not suitable optimised. However if some of these devices did not deliver the expected savings because the designs considered in this study were not sufficiently optimised, then the question arises as to whether these devices must be optimised for a specific operational conditions and how well these ESDs behave when the vessel is not operating in the design conditions

Propeller cavitation noise investigations of a research vessel using medium size cavitation tunnel tests and full-scale trials

The rising environmental awareness of various adverse emissions by commercial shipping has recently targeted Underwater Radiated Noise (URN) due to its potential impact on marine mammals. Amongst the various sources on-board a commercial ship, cavitation is the dominating one following its inception. In order to ensure acceptable noise levels for sustainable shipping, accurate prediction of the noise signature is vital. Within this framework, a widely utilized method for full-scale noise prediction is to conduct model tests in cavitation tunnels and to extrapolate to full-scale. The aim of this paper is to provide invaluable URN data of a full-scale vessel and its prediction using cavitation tests from a medium-sized tunnel to evaluate the prediction methodology. Extrapolated URN data based on the tunnel tests was compared with the data obtained from the full-scale trials with The Princess Royal in order to assess the prediction methodology. The comparisons indicate that, whilst the ideal experimental approach is to conduct such involving tests with a full-hull model in large cavitation tunnels, the medium size facilities using dummy-hull models with wake screens, can still provide a very useful means for the URN investigations with a rapid turn around and an economical way of conducting such tests

A rare cause of deep peroneal nerve palsy due to compression of synovial cyst – Case report

AbstractINTRODUCTIONSynovial cyst is a rare cause of compression neuropathy and its differential diagnosis can be misleading.PRESENTATION OF CASEThis article presents clinical, radiological, and histological findings of deep peroneal nerve palsy due to compression of a synovial cyst in a 30-year-old patient admitted with sudden drop foot.DISCUSSIONFocal nerve entrapment in lower extremity due to synovial cystis a rare entity. Differential diagnosis is important. Surgical excision is the main treatment method with high success rate.CONCLUSIONSynovial cyst compression which can be treated easily with surgical excision should be considered in rapidly progressed drop foot

An experimental investigation into the effect of Cu2O particle size on antifouling roughness and hydrodynamic characteristics by using a turbulent flow channel

Copper and copper compounds are commonly used as biocides against biofouling on surfaces exposed to seawater. Copper oxide, one of the most commonly used forms of copper biocide, can provide an efficient mechanism for fouling-free surfaces, resulting in substantial fuel savings and reduction of Greenhouse Gases (GHG) emissions. However, copper oxide is commercially formulated with different particle sizes, which can consequently lead to surfaces with different roughness conditions. The roughness effect of various sizes of copper oxide particles on the drag performance of antifouling coatings, and hence on the ship hull drag, has not been systematically studied in the past. Therefore, to investigate the effect of particle sizes on antifouling roughness and hydrodynamic characteristics, a number of different sized cuprous oxide pigments (with median size ranging from 2µm to 250µm) were applied on Newcastle University’s (UNEW) standard acrylic flat test panels. Roughness characteristics were analysed by using an optical surface profilometer. Moreover, the microstructure observations of all test specimens were carried out using Scanning Electron Microscopy (SEM). Subsequently, a laboratory experiment of streamwise pressure drop measurements was conducted on all coated plates and compared to uncoated acrylic control panels. The Reynolds number for the experiment, based on bulk mean velocity and channel height, ranged from 3×〖10〗^4 to 1.6×〖10〗^5. Analysis indicated that for the panels coated with particle sizes ≥12µm, the roughness characteristics and frictional drag increased as particle size increased. Interestingly, due to particle agglomeration and surface finish condition, those panels coated with particle sizes <12µm were found not follow this trend and had higher roughness and drag characteristics than expected

On-board measurement techniques to quantify underwater radiated noise level

Cavitating ship propellers are known to be the dominant noise source contributing significantly to the underwater radiated noise (URN) level. Innovative measurement methods using on-board devices need to be further investigated as they offer a serious alternative to traditional methods in terms of cost-efficiency and practicality. This exploratory study combined simultaneous on- and off-board noise and vibration measurements with cavitation views captured by digital photography and high speed cameras.Comprehensive full-scale trials were conducted on Newcastle University’s research vessel, The Princess Royal, in the framework of the FP7-EU project SONIC. On-board data were captured from multiple measurement systems (including. hull pressure sensors, accelerometers, optical devices, shaft strain gauges) provided by SONIC project partners CETENA, Wärtsilä , University of Southampton and Newcastle University. A new semi-empirical correlation method based on cavitating propeller pressure fluctuation and the URN level was established. Results offer clear evidence of successfully estimating URN with on-board measurements up to the middle frequency region where the blade passing fundamental and low harmonic frequencies occur. These illuminating insights reported in this paper provide valuable benchmark sea trial data in full scale

Tip vortex cavitation simulation of a propeller in a Gate Rudder® system

The GATE RUDDER® system is a novel propulsion arrangement or Energy Saving Device (ESD) inspired by the new concept of elementary propulsive efficiency and its optimization in a ship’s wake to recover more energy. The performance of a GATE RUDDER® system in the hull wake, therefore, is important not only for the efficiency but also from the cavitation, noise and vibration point of view. The World’s first gate rudder was installed on a 2,400 GT container ship in 2017 in Japan. By using the data associated with this vessel and other model test data with different ships, this paper explores the differences on the efficiency and cavitation performance of a conventional rudder and propeller system with the GATE RUDDER® system using Experimental and Computational Fluid Dynamics (EFD and CFD) approaches. There is specific emphasis on the accurate simulation of the tip vortex cavitation of the propeller in both rudder systems which has been modelled by using Yilmaz’s recently developed advanced adaptive mesh refinement approach. The results of the CFD simulations are compared with the results of the model tests conducted in the Emerson Cavitation Tunnel and the full-scale experiences with the above-mentioned container vessel as discussed in the paper