Simulation of breaking focused waves over a slope with a cfd based numerical wave tank

Extreme wave conditions are always identified with large-amplitude breaking waves in shallow waters. Focused waves can often be used to describe extreme waves which evolve during the nonlinear wave-wave interaction, occurring at one point in space and time. Under- standing breaking focused waves has many design-related implications for the design of offshore wind turbine (OWT) substructures in shallow waters. The main objective of the paper is to model breaking focused waves over a sloping seabed and study the breaking characteristics us- ing the open-source CFD model REEF3D. The numerical model describes the two-phase flow using the incompressible Reynolds-Averaged Navier-Stokes (RANS) equations together with the continuity equation. The model uses a fifth-order WENO scheme for convection discretization and a third order Runge-Kutta scheme for time discretization along with the level set method to obtain the free surface, yielding accurate wave propagation in the numerical wave tank. Solid boundaries are accounted through the ghost cell immersed boundary method. The free surface is modeled with the level set method. Turbulence is described with the two-equation k −ω model. In the numerical wave tank, the focused waves are generated using a single flap-type maker theory. The numerical results are in good agreement with experimental results for complex free surface elevations measured at several locations along the wave tank. The numerical aspects related to the development of the breaking process are investigated together with the evolution of focusing wave group in the numerical wave tank. Further, the study also examines the free surface flow features that evolve during the breaking process

A Context-Sensitive Information System for Mobile Users (Demo)

The abstract is included in the text

Early fusion and query modification in their dual late fusion forms.

In this paper, we prove that specific widely used models in Content-based Image Retrieval for information fusion are interchangeable. In addition, we show that even advanced, non-standard fusion strategies can be represented in dual forms. These models are often classified as representing early or late fusion strategies. We also prove that the standard query modification method with specific similarity measurements can be represented in a late fusion form

On the design and development of webinos: a distributed mobile application middleware.

As personal devices become smarter, opportunities arise for sharing services, applications and data between them. While web technologies hold the promise of being a unifying layer, browsers lack functionality for supporting inter-device communication, synchronization, and security. To address this, we designed webinos: a cross-device distributed middleware providing interoperability, compatibility and security for mobile web applications. In this paper we present a case study of the webinos project, showing how the architecture of webinos was specified, designed and implemented, and reflect on several lessons learned

Authorisation in Context: Incorporating Context-Sensitivity into an Access Control Framework

With sensitive information about ourselves now distributed across personal devices, people need to make access control decisions for different contexts of use. However, despite advances in improving the usability of access control for both developers and users, we still lack insights about how the intentions behind policy decisions in different contexts of use are shaped. In this paper, we describe how context was incorporated into an access control framework using a study of how context influences access control decision making. We describe how the main recommendations arising from this study were used to build context into a policy editor for this access control framework

On the duality of specific early and late fusion strategies

In this paper, we prove that specific early and specific late fusion strategies are interchangeable. In the case of the late fusion, we consider not only linear but also nonlinear combinations of scores. Our findings are important from both theoretical and practical (applied) perspectives. The duality of specific fusion strategies also answers the question why in the literature the experimental results for both early and late fusion are often similar. The most important aspect of our research is, however, related to the presumable drawbacks of the aforementioned fusion strategies. It is an accepted fact that the main drawback of the early fusion is the curse of dimensionality (generation of high dimensional vectors) whereas the main drawback of the late fusion is its inability to capture correlation between feature spaces. Our proof on the interchangeability of specific fusion schemes undermines this belief. Only one of the possibilities exists: either the late fusion is capable of capturing the correlation between feature spaces or the interaction between the early fusion operators and the similarity measurements decorrelates feature spaces

Classification of Aquaculture Locations in Norway With Respect to Wind Wave Exposure

In Norway there are a total of 1070 registered sites for salmon farming all along the coast. Trends in the aquaculture industry in the recent decade are that salmon farming sites tend to gradually relocate to more wave and current exposed locations. This trend is mainly motivated by the good water quality found in more exposed areas, as well as a lack of available sheltered locations. On the other hand, the increased exposure puts higher loads on the structures and this needs to be addressed by the development of more robust technology. The first step in order to address an increased exposure is to quantify the level of exposure of waves and current, and in this paper a method to easily estimate the level of wind wave exposure on a large number of sites are presented, and subsequently used to analyse all Norwegian sites. The method can be called fetch analysis, and use long term wind data connected with the fetch length in order to estimate wind wave conditions. The method is divided into four steps: 1) Fetch analysis, 2) Wind data, 3) Estimating wave parameters Hs and Tp and 4) Wave statistics. Significant wave height Hs with return period 1 year and 50 years are estimated for each site. Hs 50 year is often used for design, and the analysis shows that for 38% of the sites Hs 50 year exceeds 1 meter, for 17% of the sites Hs 50 year exceeds 1.5 meter, while 1.4% of the sites have Hs 50 year larger than 2.5 meter. The most exposed site has a Hs 50 year of 2.9 meter. Thus there are large differences in Hs 50 year in the various coastal regions of Norway.acceptedVersio

Characteristics and Profile Asymmetry Properties of Waves Breaking over an Impermeable Submerged Reef

In the present study, a 3D two-phase flow CFD model that solves the unsteady, incompressible Reynolds-Averaged Navier–Stokes equations has been used to simulate breaking waves over an impermeable submerged reef. The level set method is used to capture the complex free surface and the turbulence is described by the k − ω turbulence model. The numerical model was evaluated by comparing the computed results with the experimental data by Blenkinsopp and Chaplin (2008) and the computed results are in good agreement with the measured data. The computed results over the submerged reef clearly depict the flow features associated with the breaking process such as the complex interface deformation, the formation of the plunger vortex and the downstream vortex, the splash-up phenomenon and the movement of the enclosed air pocket. The main aim of the study was to investigate the effect of the offshore wave steepness and the water depth above the reef crest on the characteristics and the profile asymmetric properties of waves breaking over a submerged reef. The computed results suggest that the water depth over the reef crest affects the prominent characteristics of waves breaking over a reef such as breaker type, water depth at breaking, breaker indices and geometric properties.acceptedVersion© 2015. This is the authors’ accepted and refereed manuscript to the article. Locked until 11 April 2017 due to copyright restrictions. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0