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We frame the mechanical stress tensor decomposition in a general procedure which involves the Helmholtz–Hodge decomposition. We highlight the impact of the mechanical stress tensor decomposition on the Navier–Stokes equation, with emphasis on the dissipation function. For fluids with low compressibility, we draw some insights on the Reynolds Averaged Navier–Stokes equations, and on the Reynolds stress tensor decomposition. We derive a turbulent potential flow model, and investigate the transition from viscous potential flow to turbulent potential flow. Under low Mach number approximation, we apply the turbulent potential flow model to one-dimensional propagation of large amplitude pressure waves in liquid-filled pipe. [ABSTRACT FROM AUTHOR]

Under adiabatic conditions, and neglecting temperature variations due to entropy production, we present a set of Reynolds Averaged Navier–Stokes (RANS) equations for fluids of low compressibility, i.e., fluids in the liquid state. In the low Mach number limit, we specialize the RANS equations to the one-dimensional unsteady pipe flow, and we deduce the dimensionless number that plays a predominant role in the flow behavior. We reduce the system of equations to a linear damped wave equation, and use its analytical solution to investigate the propagation of large amplitude pressure waves in liquid-filled pipes (water hammer phenomenon). We test the model reliability by comparing the analytical solution of the proposed model against experimental data available in the literature. [ABSTRACT FROM AUTHOR]

Many marine structures are composed of vertical axisymmetric floats. In this paper, a semi-analytical model based on the linear potential flow theory and an eigenfunction expansion method is developed to study wave diffraction and radiation by an array of cylindrical structures. Each structure can be formed by three coaxial cylinders of different dimensions. Based on the semi-analytical model, a constrained matrix equation of motion is presented and solved to evaluate the performance of multiple interconnected cylindrical structures. In order to verify the accuracy of the semi-analytical model, a typical OC4-DeepCwind floating offshore wind turbine (FOWT) is selected for validation. The validated model is, then, applied to study the effect of base column submergence depth, radius, and thickness on the motion response of a semi-submersible platform. Although the results of this study are of significance for the selection of the optimum semi-submersible FOWT for specific locations (with specific prevailing wave directions), the focus of this work was placed on the semi-analytical model itself, which is efficient in modeling the interaction of the wave field and can be used in future FOWT projects. [ABSTRACT FROM AUTHOR]

In this paper, a concept of a floating elastic wave energy converter consisting of a disk-shaped elastic plate is proposed. The floating plate is moored to the seabed through a series of power take-off (PTO) units. A theoretical model based on the linear potential flow theory and eigenfunction matching method is developed to study the hydroelastic characteristics and evaluate wave power absorption of the device. The PTO system is simulated as a discrete PTO, and moreover, it is also modelled as a continuum PTO to represent the case when the PTO system is composed of a large number of PTO units. The continuum PTO approximation is tested against the discrete PTO simulation for accuracy. Two methods are proposed to predict the wave power absorption of the device. After running convergence analysis and model validation, the present model is employed to do a multiparameter impact analysis. The device adopting a continuum PTO system is found to capture wave power efficiently in an extensive range of wave frequencies. For the continuum PTO system, it is theoretically possible to adopt optimised PTO damper and stiffness/mass to guarantee the absorption of 100% of the energy flux available in one circular component of the plane incident wave. [ABSTRACT FROM AUTHOR]

We consider a finite array of floating flap gates oscillating wave surge converter (OWSC) in water of constant depth. The diffraction and radiation potentials are solved in terms of elliptical coordinates and Mathieu functions. Generated power and capture width ratio of a single gate excited by incoming waves are given in terms of the radiated wave amplitude in the far field. Similar to the case of axially symmetric absorbers, the maximum power extracted is shown to be directly proportional to the incident wave characteristics: energy flux, angle of incidence and wavelength. Accordingly, the capture width ratio is directly proportional to the wavelength, thus giving a design estimate of the maximum efficiency of the system. We then compare the array and the single gate in terms of energy production. For regular waves, we show that excitation of the out-of-phase natural modes of the array increases the power output, while in the case of random seas we show that the array and the single gate achieve the same efficiency. [ABSTRACT FROM AUTHOR]

Ankle syndesmosis injuries are relatively frequent in sports, especially skiing, ice hockey, and soccer, accounting for 1 %–18 % of all ankle sprains. The evolution is unpredictable: When missed, repeated episodes of ankle instability may predispose to early degenerative changes, and frank osteoarthritis may ensue. Diagnosis is clinical and radiological, but arthroscopy may provide a definitive response, allowing one to address secondary injuries to bone and cartilage. Obvious diastasis needs to be reduced and fixed operatively, whereas less severe injuries are controversial. Nonoperative treatment may be beneficial, but it entails long rehabilitation. In professional athletes, more aggressive surgical treatment is warranted. [ABSTRACT FROM AUTHOR]

The new means and modalities of communication and information technologies have significantly revolutionized access to surgical education. The introduction of the Internet information highway into mainstream clinical practice as an information sharing medium offers a wide range of opportunities to healthcare professionals. High‐speed Internet broadcasting allows the display of high‐quality full‐screen videos. Access to surgical procedures through the Internet already plays a major role in continuing medical education nowadays and will undoubtedly be gaining grounds in the future. WebSurg.com, the World Virtual University, a web‐based surgical university, is dedicated to minimally invasive laparoscopic surgery. Using brand‐new multimedia data, the electronic university provides thorough descriptions of over 150 procedures in minimal access surgery and 265 videos of surgical interventions. Such a teaching tool recreates all the prerequisites and requirements of a traditional School of Medicine, incorporating the manifold standpoints of world‐renowned experts about specific topics and hands‐on hints in various surgical specialities. Following the evolution of technologies, recent advances have made it possible to display items of Websurg.com on handheld devices (personal data/digital assistance also known as PDAs, Pocket PCs, and smart phones). Integrating all these elements into a unique World Virtual University, Websurg.com epitomizes the concept of a unified academic center providing teaching and tutorials administered by international experts. The Internet assuredly contributes to the worldwide diffusion of scientific information in an easy and user‐friendly way. [ABSTRACT FROM AUTHOR]

We review wave energy conversion technologies for niche applications, i.e., kilowatt-scale systems that allow for more agile design, faster deployment and easier operation than utility scale systems. The wave energy converters for niche markets analysed in this paper are classified into breakwater-integrated, hybrid, devices for special applications. We show that niche markets are emerging as a very vibrant landscape, with several such technologies having now achieved operational stage, and others undergoing full-scale sea trials. This review also includes flexible devices, which started as niche applications in the 1980s and are now close to commercial maturity. We discuss the strong potential of flexible devices in reducing costs and improving survivability and reliability of wave energy systems. Finally, we show that the use of WECs in niche applications is supporting the development of utility-scale projects by accumulating field experience, demonstrating success stories of grid integration and building confidence for stakeholders. [ABSTRACT FROM AUTHOR]

We present a novel mathematical model to investigate the extraction of wave power by flexible floaters. The model is based on the method of dry modes, coupled with a matched eigenfunction expansion. Our model results compare satisfactorily with preliminary data obtained from a demonstrator device, developed at the University of Groningen. We show that the role of elasticity is to increase the number of resonant frequencies with respect to a rigid body, which has a positive effect on wave power output. The mathematical model is then extended to irregular incident waves, described by a JONSWAP spectrum. Our results show that the peak capture factors decrease in irregular waves, as compared to the monochromatic case. However, the system becomes more efficient at non-resonant frequencies. This work highlights the need to scale-up experimental investigations on flexible wave energy converters, which are still a small minority, compared to those on rigid converters. [ABSTRACT FROM AUTHOR]