497 research outputs found
Relations for a periodic array of flap-type wave energy converters
This paper investigates the interaction of plane incident waves with a wave
farm in the open ocean. The farm consists of a periodic array of large
flap-type wave energy converters. A linear inviscid potential-flow model,
already developed by the authors for a single flap in a channel, is considered.
Asymptotic analysis of the wave field allows to obtain new expressions of the
reflection, transmission and radiation coefficients of the system. It is shown
that, unlike a line of heaving buoys, an array of flap-type converters is able
to exploit resonance of the system transverse modes in order to attain high
capture factor levels. Relations between the hydrodynamic coefficients are
derived and applied for optimising the power output of the wave farm.Comment: Accepted for publication on Applied Ocean Research, 26 Sept 201
Simulation of Free Surface Compressible Flows Via a Two Fluid Model
The purpose of this communication is to discuss the simulation of a free
surface compressible flow between two fluids, typically air and water. We use a
two fluid model with the same velocity, pressure and temperature for both
phases. In such a numerical model, the free surface becomes a thin three
dimensional zone. The present method has at least three advantages: (i) the
free-surface treatment is completely implicit; (ii) it can naturally handle
wave breaking and other topological changes in the flow; (iii) one can easily
vary the Equation of States (EOS) of each fluid (in principle, one can even
consider tabulated EOS). Moreover, our model is unconditionally hyperbolic for
reasonable EOS.Comment: 8 pages, 10 figures; OMAE2008, 27th International Conference on
Offshore Mechanics and Arctic Engineering. Other authors papers and
animations related to this work can be downloaded from:
http://www.cmla.ens-cachan.fr/fileadmin/Membres/dutykh/ The paper was
slightly modified according to referees comment
Discrete Cosserat Approach for Multi-Section Soft Robots Dynamics
In spite of recent progress, soft robotics still suffers from a lack of
unified modeling framework. Nowadays, the most adopted model for the design and
control of soft robots is the piece-wise constant curvature model, with its
consolidated benefits and drawbacks. In this work, an alternative model for
multisection soft robots dynamics is presented based on a discrete Cosserat
approach, which, not only takes into account shear and torsional deformations,
essentials to cope with out-of-plane external loads, but also inherits the
geometrical and mechanical properties of the continuous Cosserat model, making
it the natural soft robotics counterpart of the traditional rigid robotics
dynamics model. The soundness of the model is demonstrated through extensive
simulation and experimental results for both plane and out-of-plane motions.Comment: 13 pages, 9 figure
On the use of finite fault solution for tsunami generation problems
The present study is devoted to the problem of tsunami wave generation. The
main goal of this work is two-fold. First of all, we propose a simple and
computationally inexpensive model for the description of the sea bed
displacement during an underwater earthquake, based on the finite fault
solution for the slip distribution under some assumptions on the dynamics of
the rupturing process. Once the bottom motion is reconstructed, we study waves
induced on the free surface of the ocean. For this purpose we consider three
different models approximating the Euler equations of the water wave theory.
Namely, we use the linearized Euler equations (we are in fact solving the
Cauchy-Poisson problem), a Boussinesq system and a novel weakly nonlinear
model. An intercomparison of these approaches is performed. The developments of
the present study are illustrated on the 17 July 2006 Java event, where an
underwater earthquake of magnitude 7.7 generated a tsunami that inundated the
southern coast of Java.Comment: 31 pages, 10 figures, 3 tables. Other author's papers can be
downloaded at http://www.lama.univ-savoie.fr/~dutykh
On the effect of compressibility on the impact of a falling jet
At the first World Sloshing Dynamics Symposium that took place during the Nineteenth (2009) International Offshore and Polar Engineering (ISOPE) Conference in Osaka, Japan, it was made clear that simplified academic problems have an important role to play in the understanding of liquid impacts. The problem of the impact of a mass of liquid on a solid structure is considered. First the steady two-dimensional and irrotational flow of an inviscid and incompressible fluid falling from a vertical pipe, hitting a horizontal plate and flowing sideways, is considered. A parametric study shows that the flow can either leave the pipe tangentially or detach from the edge of the pipe. Two dimensionless numbers come into play: the Froude number and the aspect ratio between the falling altitude and the pipe width. When the flow leaves tangentially, it can either be diverted immediately by the plate or experience squeezing before being diverted. The profile of the pressure exerted on the plate is computed and discussed. Then the same problem is revisited with the inclusion of compressibility effects, both for the falling liquid and for the gas surrounding it. An additional dimensionless number comes into play, namely the Mach number. Finally, a discussion on the differences between the incompressible and compressible cases is provided
A Cost-Effective Method for Modelling Wave-OWSC Interaction
Bottom-hinged Oscillating Wave Surge Converters (OWSCs) are an efficient way of extracting power from ocean waves. In our previous studies, wave and OWSC interaction has been investigated via computational fluid dynamics (CFD) models. However, these models were highly time-consuming, and significant re-reflection was observed. The present work couples a Boussinesq wave model with a CFD model in order to extend the scope of the applications of the previous models. This model takes advantage of the Boussinesq wave model, which simulates the wave propagation effectively, and the CFD model, which provides the local flow details comprehensively. The model is validated by a comparison of the present results with those obtained with the pure CFD model and the experimental tank testing. The final objective of the present work is to simulate some events experienced and recorded by the full-scale prototype (Oyster 800 developed by Aquamarine Power) incorporating the real bathymetry at the Oyster 800 site.</p
Protein glycosylation as a diagnostic and prognostic marker of chronic inflammatory gastrointestinal and liver diseases
Glycans are sequences of carbohydrates that are added to proteins or lipids to modulate their structure and function. Glycans modify proteins required for regulation of immune cells, and alterations have been associated with inflammatory conditions. For example, specific glycans regulate T-cell activation, structures, and functions of immunoglobulins; interactions between microbes and immune and epithelial cells; and malignant transformation in the intestine and liver. We review the effects of protein glycosylation in regulation of gastrointestinal and liver functions, and how alterations in glycosylation serve as diagnostic or prognostic factors, or as targets for therapy
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