Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-48873 Vortrag Cuéllar, Pablo Wind energy challenges. An offshore perspective and some possible solutions This talk provides a brief introduction on general engineering challenges for the offshore (marine) wind energy production, focusing on material, structural and hydromechanical aspects. The talk begins with a broad overview on general trends for offshore wind-farms, with insights on some characteristic structural features and their associated loads. Then, some particular open issues for the foundation of the offshore wind turbines into the seabed are introduced. Here, different research approaches are discussed, from experimental investigations to coupled computational analysis at micro- and macroscopic scales. In the second part of the seminar, both the hydromechanical Wave-Tower interaction and some general aspects of the windfarm aerodynamics (wake analysis) are discussed. Some modelling possibilities in the frame of CFD (computational fluid dynamics) are introduced and the relevance of such analyses for a proper windfarm layout optimization is pointed out. Summing up, this seminar aims to show that: i) Numerical analysis of the turbine's interaction with wind/waves and with the seabed is both useful and affordable. ii) Simplified models can provide an insight into windfarm aerodynamics. iii) Turbulent wake analysis is very relevant for the windfarm layout. 2019 Bad Honnef Physics School „Energy Science – an interdisciplinary challenge“ Physikzentrum Bad Honnef, Bad Honnef, Germany 01.09.2019 06.09.2019 2019-09-09 OPUS4-59535 Vortrag Baeßler, Matthias; Cuéllar, Pablo; Schepers, Winfried VERBATIM: Project Introduction and Large Scale Experiments The presentation summarizes the scope of the joint project VERBATIM on buckling of large Monopiles. The presented work from the authors focusses on the experimental field tests of large predented piles during driving and a numerical investigation on the observed buckling behaviour. 2024 Colloquium „Buckling of Offshore Wind Energy Structures“ Berlin, Germany 14.02.2024 15.02.2024 2024-02-21 OPUS4-51729 Vortrag Cuéllar, Pablo State of the art and development perspectives of deep foundations for offshore wind converters This presentation provides an overview of the main geotechnical aspects associated with deep foundations in the context of offshore wind generation. The most common deep foundation typologies (large diameter monopiles and multipile typologies) as well as new trends under development (e.g. suction buckets) and their current limits will be briefly described. The talk concludes with a brief review of advanced topics not covered in classical pile design, such as hydromechanical coupling effects (pore pressure generation), cyclic accumulation of deformations, cyclic degradation of axial capacity or pile-setup gains. 2020 Ciclo de Conferencias: Aplicaciones de la Geotecnia en la generación de Energía. Sociedad Argentina de Ingeniería Geotécnica SAIG Online meeting 02.12.2020 2020-12-03 OPUS4-49166 Buchkapitel Baeßler, Matthias; Cuéllar, Pablo; Victor, A.; Lüddecke, F. Triantafyllidis, T. Stability and large deformations of slender structures supported by soil materials The stability and geometric nonlinearities of slender structures are a major topic in structural design. While this topic is most relevant in the field of Structural Engineering, e.g. for steel or concrete structures, only few applications take the role of soil-structure-interaction explicitly into account. The focus of this paper is placed on the impact of soil support and its modelling for the buckling analysis based on examples both for pile foundations and for railway track stability. The general interaction between steel design and the geotechnical input will be addressed. The paper discusses and summarizes a range of subtopics based on experience and current research at the author's institute. Cham, Switzerland Springer IBF KIT 2020 Recent Developments of Soil Mechanics and Geotechnics in Theory and Practice; Lecture Notes in Applied and Computational Mechanics 91 978-3-030-28515-9 355 369 10.1007/978-3-030-28516-6 2019-10-01 OPUS4-49491 Zeitschriftenartikel Benseghier, Z.; Cuéllar, Pablo; Luu, L.-H.; Delenne, J.-Y.; Bonelli, S.; Philippe, P. Relevance of Free Jet Model for Soil Erosion by Impinging Jets The surface erosion of soil samples caused by an impinging jet can be analyzed using the jet erosion test (JET), a standard experimental test to characterize the erosion resistance of soils. This paper specifically addresses the flow characteristics of a laminar impinging jet over the irregular surface of granular beds to discuss the pertinence and relevance of commonly used empirical estimations based on a selfsimilar model of a free jet. The JET is here investigated at the microscale with a coupled fluid-particle flow numerical odel featuring the lattice Boltzmann method (LBM) for the fluid phase combined with the discrete element method (DEM) for the mechanical behavior of the solid particles. The hydrodynamics of a laminar plane free jet are confronted with the results from a parametric study of jet impingement, both on solid smooth and fixed granular surfaces, that take into account variations in particle size, distance from jet origin, and jet Reynolds number. The flow characteristics at the bed surface are here quantified, including the maximal values in tangential velocity and wall shear stress, which can be regarded as the major cause of particle detachments under hydrodynamic solicitation. It is shown that the maximal velocity at the impinged surface can be described by the free jet self-similar model, provided that a simple empirical coefficient is introduced. Further, an expression is proposed for the maximal shear stress in laminar conditions, including a Blasius-like friction coefficient that is inversely proportional to the square root of the jet Reynolds number. To conclude, finally, the JET erosion of different cohesionless granular samples is analyzed, confirming that the threshold condition at the onset of granular motion is consistent with the Shields diagram and in close agreement with previous experimental results. ASCE 2020 Journal of Hydraulic Engineering 146 1 04019047 10.1061/(ASCE)HY.1943-7900.0001652 2019-11-06 OPUS4-54531 Beitrag zu einem Tagungsband Schneider, Ronald; Cuéllar, Pablo; Baeßler, Matthias Probabilistic approaches to the design and assessment of offshore foundations considering spatially varying site conditions In this contribution, we consider two applications in which probabilistic approaches can potentially complement or enhance the design and assessment of offshore wind turbine foundations. First, we illustrate in a numerical example that probabilistic modelling can be helpful in dealing with chang-es in turbine locations during the planning phase of an offshore wind farm. In this case, spatial probabilistic modelling of the ground conditions enables (a) an inference of the soil properties at the modified turbine location from field data collected at different locations across an offshore wind farm site and (b) an optimisation of further site investigations. Second, we discuss the uncer-tainties and risks associated with the installation of large diameter monopiles in soils with hetero-geneities such as strong layers and/or embedded boulders. Subsequently, we present a concept for modelling, understanding, and managing these risks based on a probabilistic model of the subgrade conditions, monopile, and subgrade-pile-interaction. ASRANet Ltd 2022 Proceedings of the 3rd International Conference on Structural Integrity for Offshore Energy Industry (SI 2021) 978-1-8383226-3-2 3rd International Conference on Structural Integrity for Offshore Energy Industry (SI 2021) Online meeting 15.11.2021 16.11.2021 9 17 2022-03-24 OPUS4-56525 Zeitschriftenartikel Benseghier, Z.; Luu, L.-H.; Cuéllar, Pablo; Bonelli, S.; Philippe, P. On the erosion of cohesive granular soils by a submerged jet: a numerical approach This paper presents an erosion interpretation of cohesive granular materials stressed by an impinging jet based on the results of a micromechanical simulation model. The numerical techniques are briefly described, relying on a two-dimensional Lattice Boltzmann Method coupled with a Discrete Element Methods including a simple model of solid intergranular cohesion. These are then used to perform a parametric study of a planar jet in the laminar regime impinging the surface of granular samples with different degrees of cohesive strength. The results show the pertinence of using a generalized form of the Shields criterion for the quantification of the erosion threshold, which is valid for cohesionless samples, through empirical calibration, and also for cohesive ones. Furthermore, the scouring kinetics are analysed here from the perspective of a selfsimilar expansion of the eroded crater leading to the identification of a characteristic erosion time and the quantification of the classical erosion coefficient. However, the presented results also challenge the postulate of a local erosion law including erodibility parameters as intrinsic material properties. The paper then reviews the main limitations of the simulation and current interpretation models, and discusses the potential causes for the observed discrepancies, questioning the pertinence of using time-averaged macroscopic relations to correctly describe soil erosion. The paper concludes addressing this question with a complementary study of the presented simulations re-assessed at the particle-scale. The resulting local critical shear stress of single grains reveals a very wide dispersion of the data but nevertheless appears to confirm the general macroscopic trend derived for the cohesionless samples, while the introduction of cohesion implies a significant but systematic quantitative deviation between the microscopic and macroscopic estimates. Nevertheless, the micro data still shows consistently that the critical shear stress does actually vary approximately in linear proportion of the adhesive force. Springer 2023 Granular Matter 25 8 1 20 10.1007/s10035-022-01289-5 2022-12-12 OPUS4-48909 Beitrag zu einem Tagungsband Kullolli, Borana; Cuéllar, Pablo; Baeßler, Matthias; Stutz, H. H. Modelling and calibration for cyclic soil-structure interface behaviour The structural performance of many geotechnical systems (e.g. axially-loaded pile foundations), depends on the shearing resistance at the soil interface, which may govern the load bearing capacity of the foundation. Experimental investigations have shown that this interaction is mainly localised within a narrow shear band next to the structure. Under cyclic loading, a contraction of the soil at the interface may arise (net volume loss), possibly leading to a stress relaxation and thus to a reduction of the load bearing capacity (the so-called friction fatigue). Based on the constitutive similarities between soil continua and interfaces, we propose here the adaption of a Generalized Plasticity model for sandy soils for the numerical analysis of interface problems. In this contribution, the results of an experimental campaign for the parameter calibration of the constitutive model are presented. The tests have been conducted with a ring shear device involving different normal stresses, roughness of the steel plates as well as cyclic loading. The new modelling approach shows promising results and has the additional practical advantage that the interface zone and the soil continuum can both be described with the same constitutive model in general boundary value problems. Glasgow, Scotland EDP Sciences 2019 92 Konferenz 7th International Symposium on Deformation Characteristics of Geomaterials Glasgow, Scotland 26.06.2019 28.06.2019 13007 13013 urn:nbn:de:kobv:b43-489096 10.1051/e3sconf/20199213007 https://creativecommons.org/licenses/by/4.0/deed.de 2019-09-11 OPUS4-53716 Beitrag zu einem Tagungsband Sanayei, Mohammad Hassan; Farhat, A.; Luu, L.-H.; Werner, L.; Rettinger, C.; Philippe, P.; Cuellar, Pablo Micromechanical framework for a 3d solid cohesion model - implementation, validation and perspectives This article presents a solid cohesion model for the simulation of bonded granular assemblies in the frame of 3D discrete element approaches (DEM). A simple viscoplastic cohesion model for 2D geometries is extended to 3D conditions, while its yield criterion is generalized as a hyper-surface in the space of bond solicitations to include torsional moments. The model is then calibrated using experimental results of uniaxial traction at both the microscopic and macroscopic scales with an artificial granular cohesive soil. The paper finally presents some simulated results on the macromechanical sample traction application and briefly discusses the model's current limitations and promising prospects for subsequent works. 2021 Proceeding - VII International Conference on Particle-Based Methods PARTICLES 2021 VII International Conference on Particle-Based Methods PARTICLES 2021 Hamburg, Germany 04.10.2021 06.10.2021 1 10 2021-11-10 OPUS4-53726 Vortrag Sanayei, Mohammad Hassan; Farhat, A.; Luu, Li-Hua; Werner, L.; Rettinger, C.; Philippe, P.; Cuellar, Pablo Micromechanical framework for a 3D solid cohesion model - Implemantation, validation and perspectives This article presents a solid cohesion model for the simulation of bonded granular assemblies in the frame of 3D discrete element approaches (DEM). A simple viscoplastic cohesion model for 2D geometries is extended to 3D conditions, while its yield criterion is generalized as a hyper-surface in the space of bond solicitations to include torsional moments. The model is then calibrated using experimental results of uniaxial traction at both the microscopic and macroscopic scales with an artificial granular cohesive soil. The paper finally presents some simulated results on the macromechanical sample traction application and briefly discusses the model's current limitations and promising prospects for subsequent works. 2021 VII International Conference on Particle-Based Methods PARTICLES 2021 Hamburg, Germany 04.10.2021 2021-11-10