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OTBArchitecture and The Built Environmen

Speeding up a mass-lumped tetrahedral finite-element method for wave propagation

Mass-lumped finite elements on tetrahedra offer more flexibility than their counterpart on hexahedra for the simulation of seismic wave propagation, but there is no general recipe for their construction, unlike as with hexahedra. Earlier, we found new elements up to degree 4 that have significantly less nodes than previously known elements by sharpening the accuracy criterion. A similar approach applied to numerical quadrature of the stiffness matrix provides a speed improvement in the acoustic case and an additional factor 1.5 in the isotropic elastic case. We present numerical results for a homogeneous and heterogeneous isotropic elastic test problem on a sequence of successively finer meshes and for elements of degrees 1 to 4. A comparison of their accuracy and computational efficiency shows that a scheme of degree 4 has the best performance when high accuracy is desired, but the one of degree 3 is more efficient at intermediate accuracy.Accepted Author ManuscriptApplied Geophysics and Petrophysic

New mass-lumped tetrahedral elements for 3D wave propagation modelling

We present a new accuracy condition for constructing mass-lumped elements. This condition is less restrictive than the one previously used and enabled us to construct new mass-lumped tetrahedral elements for 3D wave propagation modelling. The new degree-2 and degree-3 elements require significantly fewer nodes than previous versions and mass-lumped tetrahedral elements of higher degree had not been found before. We also present a new accuracy condition for evaluating the stiffness matrix-vector product. This enabled us to obtain tailored quadrature rules for the new elements that further reduce the computational cost.Applied Geophysics and Petrophysic

New higher-order mass-lumped tetrahedral elements for wave propagation modelling

We present a new accuracy condition for the construction of continuous mass-lumped elements. This condition is less restrictive than the one currently used and enabled us to construct new mass-lumped tetrahedral elements of degrees 2 to 4. The new degree-2 and degree-3 tetrahedral elements require 15 and 32 nodes per element, respectively, while currently, these elements require 23 and 50 nodes, respectively. The new degree-4 elements require 60, 61, or 65 nodes per element. Tetrahedral elements of this degree had not been found until now. We prove that our accuracy condition results in a mass-lumped finite element method that converges with optimal order in the $L^2$-norm and energy-norm. A dispersion analysis and several numerical tests confirm that our elements maintain the optimal order of accuracy and show that the new mass-lumped tetrahedral elements are more efficient than the current ones.Applied Geophysics and Petrophysic

The Glaciogenic Reservoir Analogue Studies Project (GRASP): An integrated approach to unravel genesis, infill and architecture of tunnel valleys reservoirs

Tunnel galleys are common features in Palaeozoic glacigenic succession in North Afrcica and Middle East and they are amongst the most challenging target for hydrocarbon exploration and developing drilling in these regions. Similarly, these buried valleys form important groundwater reservoirs in Quaternary glaciated areas and their nature and sediment composition is critical to drive a sustainable production strategy and assess their vulnerability. Seismic resolution however, often limits the understanding of channel valleys morphology, 3D geometry and internal reservoir distribution, thus increasing the risk associated with developing effectively these reservoirs. Therefore a analogue-based predictive stratigraphical and sedimentological model can help to steer drilling strategy and reduce uncertainties and associated risks. For this purpose the GRASP joint industry programme was established four years ago focusing on an integrated study of tunnel valley infill and architecture from the southern North Sea (UK and NL). The thorough examination of existing large subsurface and outcrop data set regarding the last 3 Pleistocene glaciations in NW Europe resulted in an improved understanding of tunnel valley genesis, sedimentary process and internal architecture. This learning can be used ultimately to improve our predictive capability when exploring and developing natural resources from these geological systems.Geoscience & EngineeringCivil Engineering and Geoscience

Wave-Skewness And Current-Related Ebb-Tidal Sediment Transport: Observations And Modeling

A combination of observations and modeling of wave-and current-related sediment transport at the ebb-tidal delta of Ameland, The Netherlands, has been used to examine the dominant sediment transport contributions shaping the ebb-tidal delta. The calibrated model shows a good comparison with the observations for a range of conditions. The results show distinctly different transport modes and directions for current and wave-dominated conditions respectively, with a significant contribution owing to the skewness of the waves emphasizing the importance of wave non-linearity in shaping the ebb-tidal delta.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Coastal EngineeringEnvironmental Fluid Mechanic

Navigatie en Geodetische Puntsbepaling met het Global Positioning System

In opdracht van: Stichting Nederlandse Genootschap voor LandmeetkundeGeodesieCivil Engineering and Geoscience