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 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.

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 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 Stability Analysis of Multiharmonic Nonlinear Vibrations for Large Models of Gas-Turbine Engine Structures With Friction and Gaps

2016 ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Frequency Domain Analysis ◽  
Gas Turbine Engine ◽  
Forced Response ◽  
Scale Model ◽  
Turbine Engine ◽  
Nonlinear Springs ◽  
Large Scale Model ◽  
The Stability

An efficient method is proposed for the multiharmonic frequency domain analysis of the stability for nonlinear periodic forced vibrations in gas-turbine engine structures and turbomachines with friction, gaps and other types of nonlinear contact interfaces. The method allows using large-scale finite element models for structural components together with detailed description of nonlinear interactions at contact interfaces between these components. The highly accurate reduced models are applied in the assessment of stability of periodic regimes for large-scale model of gas-turbine structures. An approach is proposed for the highly-accurate calculation of motion of a structure after it is perturbed from the periodic nonlinear forced response. Efficiency of the developed approach is demonstrated on a set of test cases including simple models and large-scale realistic bladed disc models with different types of nonlinearities: friction, gaps and cubic nonlinear springs.

Wave Loads of Slender Marine Cylinders Depending on Interaction Effects of Adjacent Cylinders

2006 ◽  
Author(s):  
Uwe Sparboom ◽  
Hocine Oumeraci
Keyword(s):  
Large Scale ◽  
Research Programme ◽  
Basic Research ◽  
Irregular Waves ◽  
Research Centre ◽  
Wave Loads ◽  
Freak Waves ◽  
First Results ◽  
Set Up ◽  
Coastal Research

Within a basic research programme at the Coastal Research Centre (FZK) in Hannover large-scale wave experiments were performed with single vertical and inclined Cylinders (Oumeraci, 2004). Additionally, cylinder groups were investigated with special reference to shelter and amplification effects depending on cylinder spacing. Nonbreaking regular and irregular waves as well as breaking freak waves were generated. The test set-up and some first results of the experiments looking to the maximum wave loads are reported in the paper.

Large-Scale Model Tests With Wave Loading on Offshore Platform Deck Elements

2002 ◽  
Author(s):  
Martin J. Sterndorff
Keyword(s):  
Large Scale ◽  
Model Tests ◽  
Offshore Platform ◽  
Irregular Waves ◽  
Scale Model ◽  
Wave Forces ◽  
Wave Loading ◽  
Large Wave ◽  
Wave Channel ◽  
The Individual

The present paper concerns a detailed large-scale experimental study of wave loading on offshore platform decks. A series of model tests with wave loading on different types of deck elements have been performed in the large wave channel (GWK) at Forschungszentrum Kiiste in Hannover, Germany. The following types of deck elements have been considered: tubular elements, plate profiles, and HEB beam profiles. The tests have been performed with individual elements and arrays of elements. Tests have also been performed with an array of beam elements covered with deck plating. A large range of different wave types, air gaps, and inundation’s have been tested. Regular waves with wave height ranging from 1.4 m to 1.8 m, irregular waves and wave packages with crest heights ranging from 0.9 m to 1.6 m have been tested. During the tests the following parameters were measured: wave elevations, deck element inundation’s, wave kinematics profile, and wave forces on the individual deck elements. The model test results will be analysed to provide hydrodynamic load coefficients to a wave-in-deck load programme based on the concept of change of fluid momentum. The results will also be used to verify a CFD code based on the Volume of Fluid method.

scholarly journals EXTERNAL AND INTERNAL WAVE SET-UP AT POROUS PBA REVETMENTS ON A SAND FOUNDATION

2012 ◽  
Vol 1 (33) ◽  
pp. 27
Author(s):  
Gisa Foyer ◽  
Hocine Oumeraci
Keyword(s):  
Large Scale ◽  
Wave Length ◽  
Irregular Waves ◽  
Scale Model ◽  
Large Scale Model ◽  
Internal Set ◽  
Deep Water Wave ◽  
Set Up ◽  
The Stability ◽  
Almost All

Wave set-up is generally considered for the stability analysis of beaches, but not or not explicitly for the design of revetments. Based on large-scale model results with regular and irregular waves, it is shown in this paper that this is not justified. For this purpose, the wave set-up on a porous bonded revetment and the related internal set-up in the sand foundation below the revetment are analysed for different breaker types. The results particularly show that (i) considerable set-up values are obtained for almost all breaker types, (ii) a good correlation exists with the deep water wave length for both external and internal set-up and (iii) the internal set-up is significantly affected by the wave set-up on the slope. Empirical formulae for the prediction of the external and internal set-up are also proposed for both regular and irregular waves.

Large-Scale Model Investigation for Monopile Decommissioning of Offshore Wind Turbines: Overpressure and Vibratory Pile

2021 ◽  
Author(s):  
Nils Hinzmann ◽  
Patrick Lehn ◽  
Jörg Gattermann
Keyword(s):  
Large Scale ◽  
Planning Process ◽  
Complete Removal ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbines ◽  
Large Scale Model ◽  
First Results ◽  
Set Up ◽  
Large Scale Tests

Abstract As of now, only a small number of offshore foundations, related to offshore wind energy, were decommissioned in Europe. With a diameter up to nine meter, an embedment of about 40 meter and a set up effect over 25 years, the necessary force to pull the pile out of the seabed can be assumed, if at all determinable, to be enormous. The piles that were decommissioned were cut beneath the mud line, which leaves approximately one third of the foundation permanently in the seabed. Different methods and techniques for a complete removal of offshore pile foundation are currently investigated within the project DeCoMP. Vibratory extraction aims for a reduction of the pile skin friction by creating a layer of less density between the pile shaft and pending soil. During the design and planning process for vibratory installation or extraction a drivability prediction is a key element. In order to identify and characterize soil parameter for the numerical simulation of a drivability prediction, large-scale tests are performed by the Institute of Geomechanics and Geotechnics of the Technische Universität Braunschweig (IGG-TUBS) [1]. In this paper first results of pilot tests with two vibrators are presented and key elements such as crane uplift, frequency and acceleration displayed.

scholarly journals Stability Analysis of Multiharmonic Nonlinear Vibrations for Large Models of Gas Turbine Engine Structures With Friction and Gaps

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
E. P. Petrov
Keyword(s):  
Gas Turbine ◽  
Large Scale ◽  
Frequency Domain Analysis ◽  
Gas Turbine Engine ◽  
Forced Response ◽  
Scale Model ◽  
Turbine Engine ◽  
Nonlinear Springs ◽  
Large Scale Model ◽  
The Stability

An efficient method is proposed for the multiharmonic frequency-domain analysis of the stability for nonlinear periodic forced vibrations in gas turbine engine structures and turbomachines with friction, gaps, and other types of nonlinear contact interfaces. The method allows using large-scale finite element models for structural components together with detailed description of nonlinear interactions at contact interfaces between these components. The highly accurate reduced models are applied in the assessment of stability of periodic regimes for large-scale model of gas turbine structures. An approach is proposed for the highly accurate calculation of motion of a structure after it is perturbed from the periodic nonlinear forced response. Efficiency of the developed approach is demonstrated on a set of test cases including simple models and large-scale realistic bladed disk models with different types of nonlinearities: friction, gaps, and cubic nonlinear springs.

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