Ocean space utilization

In the light of rising sea level, scarcity of land-based resources and increasingly populated coastal areas, interest of project developers and countries turns towards the ocean, exploring the possibilities of utilizing this space for various purposes. With the oceans covering roughly 70% of the Earth’s surface and more than half of the world’s population clustered in coastal areas, the oceans are a natural direction to turn to. Ocean Space Utilization (OSU), i.e., the use of ocean waters and/or the seabed for human activities, is by no means new. Shipping and fishing in ocean waters date back millennia. During the last century, aquaculture of seafood production developed into a global industry. Also, the seabed has provided minerals (mostly sand) as building material. Recently, the marine mining industry experienced a development from traditional sand dredging to deep sea mining for precious or rare mineral resources. The offshore oil and gas industry developed from first wooden platforms in the shallow coastal waters of the Gulf of Mexico to Floating Production Storage and Offloading systems and subsea equipment in more than 2000 m water depth offshore Brazil. More recently, the wind energy industry followed the steps of the oil and gas industry and moved from land-based installations first to shallow coastal waters with bottom-founded wind turbines and now starts developing offshore floating wind turbines for larger water depth and greater distances to shore. Marine Renewable Energies (MRE) including Wave Energy Converters (WEC), flow turbines for electricity production from ocean or tidal currents, and Ocean Thermal Energy Conversion (OTEC) are emerging. Another recent form of renewable energy production on the ocean are Offshore Floating Photovoltaic (OFPV) Installations (Karpouzoglou et al., 2020; Trapani & Millar, 2016; Trapani & Redón Santafé, 2015). Furthermore, marine infrastructure projects of floating airports (Suzuki, 2005), floating bridges and submerged tunnels (Moan & Eidem, 2020; Watanabe et al., 2015), floating oil storage terminals (Ueda, 2015; Zhang et al., 2020), floating logistics hubs/ports (Waals et al., 2018), a floating event stage (Koh and Lim, 2015), as well as even entire floating cities (Callebaut, 2015) are discussed in the literature. Eventually, recreational use and ocean research also belong to the broad field of Ocean Space Utilization. As an inventory of Ocean Space Utilization projects, this committee gathered as many OSU projects as possible in various stages (from concept study to commercial project) and from various fields in a project atlas based on Google maps. Offshore oil and gas projects are excluded from the atlas to prevent overloading it. Figure 1.1 shows a screenshot of the project atlas with a global overview of all projects. The projects can be grouped and color-coded by OSU field or by project status as shown in the two columns on the right of the figure. At the time of writing, this project atlas contained 235 projects. Even without offshore oil and gas projects, the energy field, comprising mainly offshore wind farms, dominates the list with 90 projects. Two other large fields of OSU are food production, i.e., mainly (offshore) aquaculture with 46 projects, and infrastructure projects (35) like floating bridges and airports. From the project list by field, it is apparent that there are many projects associated with more than one field. This signifies the new trend of multi-use ocean space utilization. An example for this multi-use is mussel farming within an offshore wind farm (see Edulis project in food & energy field). Regarding the project stage, the project entries range from mere concepts and research projects to fully operational structures. The database behind this project atlas contains more information on the individual projects with details on the field (use), project name and location, coordinates, the associated institution as well as a link for further information.publishedVersio

Combined Additive Manufacturing Techniques for Adaptive Coastline Protection Structures

Traditional reinforcement cages are manufactured in a handicraft manner and do not use the full potential of the material, nor can they map from optimised geometries. The shown research is focused on robotically-manufactured, structurally-optimised reinforcement structures which are prefabricated and can be encased by concrete through SC3DP in a combined process. Based on the reinforcement concept of “reinforcement supports concrete,” the prefabricated cages support the concrete during application in a combined AM process. To demonstrate the huge potential of combined AM processes based on the SC3DP and WAAM techniques (for example, the manufacturing of individualized CPS), the so-called FLOWall is presented here. First, the form-finding process for the FLOWall concept based on fluid dynamic simulation is explained. For this, a three-step strategy is presented, which consists of (i) the 3D modelling of the element, (ii) the force-flow analysis, and (iii) the structural validation in a computational fluid dynamics software. From the finalized design, the printing phase is divided into two steps, one for the WAAM reinforcement and one for the SC3DP wall. The final result provides a good example of efficient integration of two different printing techniques to create a new generation of freeform coastline protection structures

Modellierung und Analyse von Wellen-Bauwerk-Boden Interaktion für monolithische Wellenbrecher

Monolithic breakwaters are preferred to other types of structures in terms of economical and environmental aspects. Nevertheless, they are more vulnerable to foundation failures, especially to stepwise failures. Due to the highly complex processes involved in wave-structure-foundation interaction, no reliable model yet exists for this failure mechanism. Therefore, a semi-coupled CFD-CSD model system and a simplified model are developed in OpenFOAM to describe wave-structure-foundation interaction for monolithic breakwaters, and particularly stepwise failures. The CFD model is an extension of the incompressible multiphase Eulerian solver of OpenFOAM by introducing different seepage laws and a simplified fluid compressibility model. The CFD model is successful in reproducing breaking wave impact including effect of entrapped air. A new CSD model is developed to solve the fully dynamic, coupled Biot equations with a new approach taking advantage of the PISO algorithm to resolve pore fluid velocity-pressure coupling. Soil-structure interaction is introduced via a frictional contact model and for soil behaviour, a multi-surface plasticity model is implemented. The model is validated against analytical models and physical tests. The model succeeds to reproduce wave-induced residual pore pressure buildup and soil densification followed by pore pressure dissipation. A one-way coupling of both models is achieved by transforming the CFD model output into input for the CSD model. The semi-coupled model system is applied successfully to reproduce selected results of a caisson breakwater subject to breaking wave impact in the Large Wave Flume (GWK). The model system is applied to expand the range of conditions tested in GWK for response of the soil foundation. A new load eccentricity concept, is proposed to classify response of the foundation in four load eccentricity regimes. Load eccentricity carries all significant information related to wave loads (horizontal and uplift) and to properties of the structure (mass and geometry). Using this concept, recommendations are drawn for design of monolithic breakwaters, and a new simplified nonlinear 3-DOF model is developed with elastoplastic springs. Model parameters are calibrated using results from the CFD-CSD model for different sand relative densities and different load eccentricities. The simplified model can simulate the stepwise failure (sliding, settlement and tilt) as well as the overall failure (overturning).Caisson-Wellenbrecher werden aufgrund ökonomischer und Umweltaspekte bevorzugt. Jedoch sind sie empfindlicher gegen das Versagen des Baugrundes insbesondere gegen schrittweises Versagen. Aufgrund der Komplexität der Wellen-Bauwerk-Boden Interaktion liegt noch kein verlässliches Modell für diesen Versagensmechanismus vor. Deswegen werden ein semi-gekoppeltes CFD-CSD Modellsystem und ein vereinfachtes Modell in OpenFOAM entwickelt. Das CFD-Modell stellt eine durch Sickerströmungsgesetze und ein vereinfachtes Modell der Fluidkompressibilität erweiterte Version des mehrphasigen Strömingslösers von OpenFOAM dar. Das CFD-Modell wurde erfolgreich eingesetzt, um Druckschlagbelastungen durch brechende Wellen mit Lufteinschlüssen zu reproduzieren. Ein neues CSD-Modell wurde für die Lösung der voll dynamischen, gekoppelten Biot-Gleichungen mit einem neuen Ansatz entwickelt. Dabei wird der PISO-Algorithmus genutzt, um die Kopplung von Geschwindigkeit und Druck des Porenfluids zu lösen. Die Bauwerk-Boden Interaktion wird über ein Reibungs-Kontaktmodell eingeführt und für die Plastizität des Bodens ein Mehrflächenmodell implementiert. Die Validierung des CSD-Modells erfolgte durch analytische Modelle und Laborversuche. Mit dem Modell ist es gelungen, den Porenwasserdruckaufbau, die Bodenverdichtung und die Dissipation des Porenwasserdruckes zu reproduzieren. Es wurde eine Einweg-Kopplung der Modelle implementiert, in dem der Output des CFD-Modells als Input für das CSD-Modell aufbereitet wird. Mit dem validierten semi-gekoppelten Modellsystem ist es gelungen die Experimente im Großen Wellenkanal (GWK) zu reproduzieren. Darüber hinaus wurde das Modellsystem eingesetzt, um die getesteten Bedingungen zu erweitern. Ein neues Lastexzentrizitätskonzept wurde eingeführt, um die Gründungsverhaltens in vier Regime zu klassifizieren. Die Lastexzentrizität fasst alle relevanten Informationen der Wellenbelastung (Horizontal und Auftrieb) und der Bauwerkseigenschaften (Masse und Geometrie) zusammen. Unter Anwendung dieses Konzepts werden Empfehlungen für die Bemessung monolithisches Wellenbrechers ausgesprochen. Darüber hinaus wurde ein vereinfachtes nichtlineares 3-DOF Modell mit elasto-plastischen Federn entwickelt. Die Modellparameter wurden für unterschiedliche relative Dichte des Bodens und Lastexzentrizität kalibriert. Das vereinfachte Modell kann das schrittweise Versagen (Gleiten, Setzung und Kippen) sowie das Gesamtversagen (Umkippen) simulieren

Análisis de movimientos y aceleraciones provocados por las acciones del oleaje y de los buques en el dique de Botafoc (Ibiza)

El reciente desarrollo de la instrumentación diseñada para proporcionar datos de aceleraciones y movimientos del cajón número 8 del dique Botafoc (Ibiza), perteneciente a la Autoridad Portuaria de Baleares (Puertos del Estado), en conjunción con datos procedentes de una instrumentación compuesta por sensores de presión existente en el paramento vertical, proporciona un novedoso medio para analizar la respuesta estructural del cajón, no sólo ante la acción del oleaje, sino también ante los efectos producidos por las maniobras de los buques en el muelle. Como la medición de estas aceleraciones y velocidades angulares se hace a altas frecuencias (de hasta 400 Hz), podemos proporcionar datos válidos acerca del comportamiento estructural y de los movimientos reales del cajón, tratando de correlacionar este comportamiento con los resultados obtenidos por el grupo de trabajo PROVERBS (Probabilistic design of vertical breakwaters, MAST III EU Programme), y generando una base de datos estadística de movimientos que deben considerarse para enriquecer los conocimientos en este ámbito. Además, la posibilidad de registrar los efectos causados por las maniobras de atraquedesatraque-estancia de los buques, abre un nuevo punto de vista al diseño estructural de un dique-muelle, siendo también de gran interés para los diseñadores de obras marítimas y para la correcta definición de las maniobras del buque en el muelle. The recent deployment of new instrumentation designed to provide accelerations and angular velocities from caisson #8 at Botafoc seawall, Ibiza, along with an existing pressure sensor instrumentation at the vertical wall, provides a way to record and process data of the structural response, not only to waves, but also to effects caused by ship mooring operations at Botafoc seawall. As the measurement of these angular speeds and accelerations is programmed with sampling frecuencies up to 400 Hz, and by integrating all data through time we may provide suitable data of the structural behaviour of the caisson. This behaviour is tried to be correlated with the PROVERBS working group achievements (Probabilistic design of vertical breakwaters, MAST III EU Programme), generating a statistical movement database that must be used to improve knowledge on this subject. Also the possibility to record the effects caused by the different ship mooring operations is a new point of view of the complete structural design of a seawall-wharf, which is considered an interesting matter for coastal designers as well for a correct ship mooring processes definition