scholarly journals BONDED POROUS REVETMENTS – EFFECT OF POROSITY ON WAVE-INDUCED LOADS AND HYDRAULIC PERFORMANCE

2012 ◽  
Vol 1 (33) ◽  
pp. 45 ◽  
Author(s):  
Sven Liebisch ◽  
Juan Carlos Alcérreca Huerta ◽  
Andreas Kortenhaus ◽  
Hocine Oumeraci
Keyword(s):  
Large Scale ◽  
Hydraulic Performance ◽  
Primary Objective ◽  
Scale Model ◽  
Large Wave ◽  
Wave Flume ◽  
Wide Range ◽  
First Results ◽  
The Stability ◽  
Wave Induced

The porosity and roughness of bonded revetments are both crucial for the hydraulic performance and the wave loading of the revetment and its foundation, and thus for the stability and durability of the entire structure. This is briefly shown by the selected results of a tentative comparative analysis of two large-scale test series performed in the Large Wave Flume (GWK) Hanover with two significantly different revetments: a highly porous and rough polyurethane bonded aggregate (PBA) revetment and an almost impermeable and relatively smooth interlocked pattern placed block (IPPB) revetment. These results motivated the initiation of the three years research project BoPoRe (Bonded Porous Revetments) which has the primary objective to investigate more systematically and separately the relative importance of both porosity and roughness for different slope steepnesses. This project is briefly introduced and the first results of preliminary scale model tests using 9 configurations for the porosity and roughness of the revetment subject to a wide range of wave conditions (surf similarity parameters 0.93-7.21) are briefly discussed.

Large-Scale Investigations of Geotextile Sandcontainers Used for Scour Protection of Offshore Monopiles Supporting Wind Energy Turbines

2006 ◽  
Author(s):  
Joachim Gru¨ne ◽  
Uwe Sparboom ◽  
Reinold Schmidt-Koppenhagen ◽  
Zeya Wang ◽  
Hocine Oumeraci
Keyword(s):  
Large Scale ◽  
Research Programme ◽  
Scale Model ◽  
Research Centre ◽  
Large Wave ◽  
Wave Channel ◽  
Large Scale Model ◽  
First Results ◽  
The Stability ◽  
Scour Protection

An innovative scour protection for monopile structures was proposed by using geotextile sand containers in a research programme started recently. Large-scale model tests on the stability of such alternative scour protection are being performed in the Large Wave Channel (GWK) of the Coastal Research Centre (FZK). First results are reported from basic test series performed with single geotextile sand containers and container groups with different container weights, varied in sizes and percentages of filling. Further an empirical approach on the stability of sand containers is estimated as a first approximation from the results.

scholarly journals WAVE LOADS ON AND BENEATH BONDED PERMEABLE REVETMENTS

2011 ◽  
Vol 1 (32) ◽  
pp. 17
Author(s):  
Gisa Ludwigs ◽  
Hocine Oumeraci ◽  
Tijl Staal
Keyword(s):  
Large Scale ◽  
Water Structure ◽  
Scale Model ◽  
Research Centre ◽  
Wave Loads ◽  
Large Wave ◽  
Wave Flume ◽  
Large Scale Model ◽  
Wide Range ◽  
Coastal Research

Permeable revetments made of bonded mineral aggregates may increasingly be favoured compared to standard revetments. However, the physical processes associated with the water–structure–soil-interaction for a wide range of wave conditions are still not well understood. Therefore, systematic large-scale model tests have been performed in the Large Wave Flume (GWK) of the Coastal Research Centre (FZK) in Hannover, with the intention of improving the understanding of these processes.

scholarly journals Experimental Investigation of Wave-Induced Ship Hydroelastic Vibrations by Large-Scale Model Measurement in Coastal Waves

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Jialong Jiao ◽  
Huilong Ren ◽  
Shuzheng Sun ◽  
Christiaan Adika Adenya
Keyword(s):  
Large Scale ◽  
Testing Procedure ◽  
Scale Model ◽  
Sea Waves ◽  
Load Pressure ◽  
Large Scale Model ◽  
Wide Range ◽  
Hydroelastic Vibrations ◽  
Wave Induced ◽  
Model Measurement

Ship hydroelastic vibration is an issue involving mutual interactions among inertial, hydrodynamic, and elastic forces. The conventional laboratory tests for wave-induced hydroelastic vibrations of ships are performed in tank conditions. An alternative approach to the conventional laboratory basin measurement, proposed in this paper, is to perform tests by large-scale model measurement in real sea waves. In order to perform this kind of novel experimental measurement, a large-scale free running model and the experiment scheme are proposed and introduced. The proposed testing methodology is quite general and applicable to a wide range of ship hydrodynamic experimental research. The testing procedure is presented by illustrating a 5-hour voyage trial of the large-scale model carried out at Huludao harbor of China in August 2015. Hammer tests were performed to identify the natural frequencies of the ship model at the beginning of the tests. Then a series of tests under different sailing conditions were carried out to investigate the vibrational characteristics of the model. As a postvoyage analysis, load, pressure, acceleration, and motion responses of the model are studied with respect to different time durations based on the measured data.

scholarly journals LOADING OF VERTICAL WALLS BY OVERTOPPING BORES USING PRESSURE AND FORCE SENSORS - A LARGE SCALE MODEL STUDY

2012 ◽  
Vol 1 (33) ◽  
pp. 44 ◽  
Author(s):  
Karunya Ramachandran ◽  
Rebeca Roldan Genzalez ◽  
Hocine Oumeraci ◽  
Stefan Schimmels ◽  
Matthias Kudella ◽  
...  
Keyword(s):  
Large Scale ◽  
Vertical Wall ◽  
Pressure Sensors ◽  
Scale Model ◽  
Force Sensors ◽  
Research Project ◽  
Joint Research ◽  
Large Wave ◽  
Wave Flume ◽  
Joint Research Project

This study is based on the data obtained from tests carried out in the Large Wave Flume (Grosser Wellenkanal (GWK)) in Hannover in the frame of a joint research project of Ghent University (Belgium) and Forschungszentrum Küste (FZK, Germany). The goal of the research project is to determine the wave induced loads on vertical storm walls located at the end of overtopped dike, which are designed to protect coastal cities from overtopping and floods. The loads resulting from waves overtopping the dike and impacting the vertical wall as a bore are measured by means of both force and pressure sensors. This paper describes the results of pressure and force records at the vertical wall, including a comparative analysis of the overall forces obtained by pressure integration and force sensors for two different wall setups: Fully blocked wall and partially blocked wall.

scholarly journals HYDRAULIC PERFORMANCE OF ELASTOMERIC BONDED PERMEABLE REVETMENTS AND SUBSOIL RESPONSE TO WAVE LOADS

2011 ◽  
Vol 1 (32) ◽  
pp. 22
Author(s):  
Hocine Oumeraci ◽  
Tijl Staal ◽  
Saskia Pfoertner ◽  
Matthias Kudella ◽  
Stefan Schimmels ◽  
...  
Keyword(s):  
Large Scale ◽  
Hydraulic Performance ◽  
Soil Liquefaction ◽  
Scale Model ◽  
Research Centre ◽  
Wave Loads ◽  
Large Scale Model ◽  
Wide Range ◽  
Physically Based ◽  
Run Up

Elastomeric bonded permeable revetments, also called PBA (Polyurethane bonded aggregate) revetments, are highly porous structures made of mineral aggregates (e.g. crushed stones) which are durably and elastically bonded by polyurethane (PU). Despite their numerous advantages as compared to conventional revetments and the large experience available from more than 25 pilot projects, physically-based design formulae to predict their hydraulic performance, wave loading and response are still lacking. Therefore, the present study aims at improving the understanding of the processes involved in the interaction between wave, revetment and foundation, based on large-scale model tests performed in the Coastal Research Centre (FZK), Hannover/Germany, and to provide prediction formulae/diagrams. This paper is focused on the prediction of the hydraulic performance (wave reflection, wave run-up and run-down) and the response of the sand core (pore pressure and effective stress) beneath the revetment for a wide range of wave conditions, including the analysis of an observed failure due to transient soil liquefaction.

Small and Large Scale Experimental Investigations of Wave Loads on a Slender Pile Within Closely Spaced Neighbouring Piles

2014 ◽  
Author(s):  
Lisham Bonakdar ◽  
Hocine Oumeraci
Keyword(s):  
Laboratory Tests ◽  
Large Scale ◽  
Model Tests ◽  
Scale Model ◽  
Research Centre ◽  
Experimental Investigations ◽  
Small Scale ◽  
Wave Loads ◽  
Large Wave ◽  
Wave Flume

Wave loads on a slender pile within a group of piles are studied by means of (i) large-scale laboratory tests carried out in the Large Wave Flume (GWK) of the Coastal Research Centre (FZK) in Hannover, and (ii) small scale experiments performed in 2 m-wide wave flume of Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI), in Braunschweig, Germany. The small scale model tests (LWI) were scaled down (1:6.5) by Froude law from the large scale model tests (GWK). Scale and model effects are examined by comparing the results of small and large scale laboratory tests.

scholarly journals WAVE LOADS ON EXPOSED JETTIES: DESCRIPTION OF LARGE SCALE EXPERIMENTS AND PRELIMINARY RESULTS

2011 ◽  
Vol 1 (32) ◽  
pp. 18 ◽  
Author(s):  
Luca Martinelli ◽  
Alberto Lamberti ◽  
Maria Gabriella Gaeta ◽  
Matteo Tirindelli ◽  
John Alderson ◽  
...  
Keyword(s):  
Large Scale ◽  
Research Team ◽  
Scale Effects ◽  
Wave Loads ◽  
Large Wave ◽  
Preliminary Results ◽  
Wave Flume ◽  
Air Content ◽  
Wave Induced ◽  
The Impact

The large scale experiments described in this paper were carried out at the Large Wave Flume (GWK, Große Wellenkanal) in Hanover (Germany). The research team included Universities of Bologna (IT), Edinburgh (UK), Southampton (UK), Plymouth (UK), HR Wallingford (UK) and Coast & Harbor Engineering Inc (USA). Wave-induced loads on close-to-prototype scale jetties were measured, with particular attention to scale effects due to air content in water. The aim of the paper is to present the tests, describe the impact process and give preliminary results concerning uplift loads.

scholarly journals No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 4
Author(s):  
Evgeny Mikhailov ◽  
Daniela Boneva ◽  
Maria Pashentseva
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Point Of View ◽  
Accretion Discs ◽  
Wide Range ◽  
Astrophysical Objects ◽  
Alpha Effect ◽  
The Stability ◽  
The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

scholarly journals Star formation thresholds derived From THINGS

2006 ◽  
Vol 2 (S237) ◽  
pp. 397-397
Author(s):  
F. Bigiel ◽  
F. Walter ◽  
E. de Blok ◽  
E. Brinks ◽  
B. Madore
Keyword(s):  
Star Formation ◽  
Large Scale ◽  
Gravitational Instability ◽  
Critical Density ◽  
Nearby Galaxy ◽  
Uv Emission ◽  
Radial Profiles ◽  
Wide Range ◽  
First Results ◽  
Type Mass

AbstractWe present first results from THINGS (The HI Nearby Galaxy Survey), which consists of high quality HI maps obtained with the VLA of 34 galaxies across a wide range of galaxy parameters (Hubble type, mass/luminosity). We compare the distribution of HI to the UV emission in our sample galaxies. In particular we present radial profiles of the HI (tracing the neutral interstellar medium) and UV (mainly tracing regions of recent star formation) in our sample galaxies. The azimuthally averaged HI profiles are compared to the predicted critical density above which organized large-scale star formation is believed to start (this threshold is based on the Toomre-Q parameter, which in turn is a measure for local gravitational instability).

Large Eddy Simulations of Staggered Parallel-Plate Flows

2005 ◽  
Author(s):  
M. V. Pham ◽  
F. Plourde ◽  
S. K. Doan
Keyword(s):  
Heat Transfer ◽  
Numerical Simulations ◽  
Heat Transfer Enhancement ◽  
Parallel Plate ◽  
Large Scale ◽  
Primary Objective ◽  
Transfer Enhancement ◽  
Turbulent Structures ◽  
Wide Range ◽  
Large Eddy

Heat transfer enhancement is a subject of major concern in numerous fields of industry and research. Having received undivided attention over the years, it is still studied worldwide. Given the exponential growth of computing power, large-scale numerical simulations are growing steadily more realistic, and it is now possible to obtain accurate time-dependent solutions with far fewer preliminary assumptions about the problems. As a result, an increasingly wide range of physics is now open for exploration. More specifically, it is time to take full advantage of large eddy simulation technique so as to describe heat transfer in staggered parallel-plate flows. In fact, from simple theory through experimental results, it has been demonstrated that surface interruption enhances heat transfer. Staggered parallel-plate geometries are of great potential interest, and yet many numerical works dedicated to them have been tarnished by excessively simple assumptions. That is to say, numerical simulations have generally hypothesized lengthwise periodicity, even though flows are not periodic; moreover, the LES technique has not been employed with sufficient frequency. Actually, our primary objective is to analyze turbulent influence with regard to heat transfers in staggered parallel-plate fin geometries. In order to do so, we have developed a LES code, and numerical results are compared with regard to several grid mesh resolutions. We have focused mainly upon identification of turbulent structures and their role in heat transfer enhancement. Another key point involves the distinct roles of boundary restart and the vortex shedding mechanism on heat transfer and friction factor.

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