A wind field downscaling strategy based on domain segmentation and transfer functions

This paper presents a novel methodology for mesoscale‐to‐microscale downscaling of near‐surface wind fields. The model chain consists on the Weather Research and Forecast mesoscale model and the Alya‐CFDWind microscale model (assuming neutral stability). The downscaling methodology combines precomputed microscale simulations with a mesoscale forecast using a domain segmentation technique and transfer functions. As a result, the downscaled wind field preserves the mesoscale pattern but, at the same time, incorporates local mesoscale subgrid terrain effects, particularly at valleys and channelling zones. The methodology has been validated over a 9‐month period on a very complex terrain site instrumented with a dense observational network of meteorological masts. With respect to mesoscale results, the global skills of the downscaled wind at masts improve for wind direction and remain similar for wind velocity. However, a substantial improvement occurs under stable and neutral conditions and for high wind velocity regimes.This work has been partially funded by the High Performance Computing for Energy (HPC4E) project (call H2020-EUB-2015, Topic: EUB-2-2015, type of action RIA, Grant Agreement number 689772) and the SEDAR ("Simulación eólica de alta resolución") project. It has also been partially supported by the Energy-oriented Centre of Excellence (EoCoE) (Grant Agreement number 676629, funded within the H2020 framework of the EuropeanUnion). J.B. is grateful to a PhD fellowship from the IndustrialDoctorates Plan of the Government of Catalonia (Ref. eco/2497/2013). We also thank Daniel Paredes and Luis Prieto from Iberdrola Renovables S.A. for providing us access to met masts data for validation.Peer ReviewedPostprint (published version

Design of an enhanced air data sensor for a very light aircraft

This project is the following part of a previous thesis about the design, development and implementation of a data acquisition system: “Development of an Integrated Flight Test Instrumentation System for Ultra Light Machines” called Mnemosine by Alberto Rolando. Participating in the improvement of the part Urania. Once the new design was decided and the implementation was done, the calibration of the new Pitot – boom has become a critical part where the pressure sensors, temperature sensor and the Pitot tube has been analyzed and tested in a wind tunnel. In this document the pre-documentation for the experimental test, the results and conclusions including the elaboration of a program in Matlab in order to calculate those important magnitudes and to show in an easier way all the results is presented

Model validation and data insertion with FALL3D-8.0: exploiting geostationary satellite retrievals of volcanic ash and SO2

The new version of FALL3D has recently been released with several new features and improvements in model physics, solving algorithms, code accuracy and performance [1]. Among the new features are a data insertion scheme and the ability to simulate volcanic SO2 clouds. The data insertion scheme enables users to initialise model runs from satellite retrievals. This modelling approach is useful for removing uncertainties associated with source term parameters such as the mass flow rate, plume height, source duration and start time. Here we demonstrate and validate the new data insertion scheme in FALL3D-8.0 using geostationary satellite retrievals of volcanic ash and SO2

Numerical modeling of magma withdrawal during explosive caldera-forming eruptions

We propose a simple physical model to characterize the dynamics of magma withdrawal during the course of caldera-forming eruptions. Simplification involves considering such eruptions as a piston-like system in which the host rock is assumed to subside as a coherent rigid solid. Magma behaves as a Newtonian incompressible fluid below the exsolution level and as a compressible gas-liquid mixture above this level. We consider caldera-forming eruptions within the frame of fluid-structure interaction problems, in which the flow-governing equations are written using an arbitrary Lagrangian-Eulerian (ALE) formulation. We propose a numerical procedure to solve the ALE governing equations in the context of a finite element method. The numerical methodology is based on a staggered algorithm in which the flow and the structural equations are alternatively integrated in time by using separate solvers. The procedure also involves the use of the quasi-Laplacian method to compute the ALE mesh of the fluid and a new conservative remeshing strategy. Despite the fact that we focus the application of the procedure toward modeling caldera-forming eruptions, the numerical procedure is of general applicability. The numerical results have important geological implications in terms of magma chamber dynamics during explosive caldera-forming eruptions. Simulations predict a nearly constant velocity of caldera subsidence that strongly depends on magma viscosity. They also reproduce the characteristic eruption rates of the different phases of an explosive calderaforming eruption. Numerical results indicate that the formation of vortices beneath the ring fault, which may allow mingling and mixing of parcels of magma initially located at different depths in the chamber, is likely to occur for low-viscosity magmas. Numerical results confirm that exsolution of volatiles is an efficient mechanism to sustain explosive caldera-forming eruptions and to explain the formation of large volumes of ignimbrites

A CFD framework for offshore and onshore wind farm simulation

We present a wind simulation framework for offshore and onshore wind farms. The simulation framework involves an automatic hybrid high-quality mesh generation process, a pre-processing to impose initial and boundary conditions, and a solver for the Reynolds Averaged Navier-Stokes (RANS) equations with two different turbulence models, a modified standard k-epsilon model and a realizable k-epsilon model in which we included the Coriolis effects. Wind turbines are modeled as actuator discs. The wind farm simulation framework has been implemented in Alya, an in-house High Performance Computing (HPC) multi-physics finite element parallel solver. An application example is shown for an onshore wind farm composed of 165 turbines.This work has been supported by the EU H2020 projects New European Wind Atlas ERA-NET PLUS (NEWA), High Performance Computing for Energy (HPC4E, grant agreement 689772), and the Energy oriented Centre of Excellence (EoCoE, grant agreement 676629). We also thank two anonymous reviewers for their constructive comments on the first version of the manuscript.Peer ReviewedPostprint (published version

Representing Urban Geometries for Unstructured Mesh Generation

AbstractWe present a robust and automatic method to generate an idealized surface geometry of a city landscape ready to be meshed for computer simulations. The city geometry is idealized for non viscous flow simulations and targets two main geometrical features: the topography and the city blocks. The procedure is fully automatic and demands no human interaction given the following source data: the city cadastre, a Digital Elevation Model (DEM) of all the target domain, and Light Detection And Ranging (LiDAR) data of the domain region covered by the cadastre. The geometry representation takes three main steps. First, a 2D mesh of the cadastre is generated, where the elements are marked according to street and block regions. Second, using a DEM of the city landscape the topography surface mesh is generated by finding the best surface mesh in the least-squares sense obtained by deforming the previous 2D mesh. Third, we extrude the block facades and we compute a planar ceiling taking into account all the buildings belonging to that city block. We describe the applicability of the geometry representation by presenting the work-flow required to generate an unstructured mesh valid for non-viscous flow or transport simulations. Finally, we illustrate the main application by obtaining a surface and tetrahedral mesh for the city of Barcelona in Spain

Análisis de la figura del agente consignatario en la casuística y operativa de un buque tramp en su escala en puerto

El objetivo principal de este proyecto de fin de grado es analizar y comprender de primera mano la figura del Agente Consignatario de un buque Tramp cuando escala en Puerto. Esta figura del sector marí­timo a simple vista parece abstracta y poco conocida aunque lleva asignada muchos temas, es decir, se encuentra justo en el medio de la cadena logÃística del transporte, no cabe duda que es difí­cil de asimilar. Es por eso que se detallara exactamente cual es su función y su actuación en el Tramping. Para ello, se tratara de poner al lector en situación con la evolución del Transporte Marí­timo hasta la actualidad, definiendo y analizando todos los conceptos generales y especí­ficos que engloban la operativa de cualquier buque Tramp utilizando fuentes de las empresas del sector en las que he trabajado, apuntes de la universidad y basándonos en la experiencia adquirida como Agente de buques Tramp en Puerto de Tarragona. Además de realizar dos casos prácticos de dos operativas, una de carga y otra de descarga de dos buques. El resultado pretende ser una guía para entender a fondo el trabajo del Agente Consignatario especializado en buques Tramp de todo tipo de mercaderías adquiriendo del mismo modo una visión global de todos los procesos documentales utilizados en este sector tan grande y poco conocido. La conclusión más importante que se puede sacar de este trabajo es que a pesar de que la industria naviera, en general es poco conocida y con frecuencia mal interpretada, las figuras marí­timas que forman parte de la cadena logística del transporte intermodal son de vital importancia para su adecuado funcionamiento poniendo énfasis en el Agente Consignatario de buques

A Novel approach to reconstruct the plinian and co-ignimbrite phases of large eruptions - Campanian Ignimbrite

Reconstructing the volume and tephra dispersal from volcanic super-eruptions is necessary to assess the widespread impact of these massive events on climate, ecosystems and humans. Recent studies have demonstrated that volcanic ash transport and dispersion models are unrivaled in accurately constraining the volume of material ejected and provide further insight about the eruption dynamics during these gigantic events. However, the conventional simplified characterization of caldera-forming supereruptions as a single-phase event can lead to inaccurate estimations of the eruption dynamics and its impacts. Here, we apply a novel computational inversion method to reconstruct, for the first time, the two phases of the largest eruption of the last 200 ky in Europe, the Campanian Ignimbrite (CI) super-eruption. Additionally, we discuss the eruption’s contribution to the Middle to Upper Paleolithic transition by evaluating its environmental and climate implications

Future developments in modelling and monitoring of volcanic ash clouds: outcomes from the first IAVCEI-WMO workshop on Ash Dispersal Forecast and Civil Aviation

As a result of the serious consequences of the 2010 Eyjafjallajökull eruption (Iceland) on civil aviation, 52 volcanologists, meteorologists, atmospheric dispersion modellers and space and ground-based monitoring specialists from 12 different countries (including representatives from 6 Volcanic Ash Advisory Centres and related institutions) gathered to discuss the needs of the ash dispersal modelling community, investigate new data-acquisition strategies (i.e. quantitative measurements and observations) and discuss how to improve communication between the research community and institutions with an operational mandate. Based on a dedicated benchmark exercise and on 3days of in-depth discussion, recommendations have been made for future model improvements, new strategies of ash cloud forecasting, multidisciplinary data acquisition and more efficient communication between different communities. Issues addressed in the workshop include ash dispersal modelling, uncertainty, ensemble forecasting, combining dispersal models and observations, sensitivity analysis, model variability, data acquisition, pre-eruption forecasting, first simulation and data assimilation, research priorities and new communication strategies to improve information flow and operational routines. As a main conclusion, model developers, meteorologists, volcanologists and stakeholders need to work closely together to develop new and improved strategies for ash dispersal forecasting and, in particular, to: (1) improve the definition of the source term, (2) design models and forecasting strategies that can better characterize uncertainties, (3) explore and identify the best ensemble strategies that can be adapted to ash dispersal forecasting, (4) identify optimized strategies for the combination of models and observations and (5) implement new critical operational strategie