Urban Air Quality Modelling using Finite Elements

[EN]Urban air quality simulation requires models with di erent characteristics to those used in mesoscale or microscale. The spatial discretisation resolution is one of them. Urban geometries require smaller elements than those in other scales. Mesh for this kind of geometries are generated using the Meccano method; a mesh generator that has generated high-quality meshes of complex geometries [1]. In this work, we have added capabilities to insert buildings into the mesh maintaining the element quality. Wind eld should also be suitable for urban scale. To this end, we will use a mass-consistent model [2]. Thisapproximation has performed e ciently in microscale problems, coupling with mesoscale numerical weather prediction models. Finally, an adaptive nite element method is used to simulate the convection-di usion-reaction equation [3, 4]. The problem can be convectiondominant, so it is stabilised using a Least-Squares nite element method. The resulting matrix is symmetric and is solved using the Conjugate Gradient method preconditioned with an incomplete Cholesky factorisation. The model is applied to the city of Las Palmas de Gran Canaria

Parallel optimization of tetrahedral meshes

[EN]We propose a new algorithm on distributed-memory parallel computers for our simultaneous untangling and smoothing of tetrahedral meshes [9, 10]. A previous parallel implementation on shared-memory computers is analyzed in [1]. The new parallel procedure takes ideas from Freitag et al. strategy [11]. The method is based on: partitioning a mesh, optimizing interior vertices, optimizing boundary vertices of interior partitions, and communicating updated coordinates of boundary vertices. This paper presents performance evaluation results of our parallel algorithm. We apply the procedure in the mesh generation of several 3-D objects by using the Meccano method [4]. High levels of speed-up are obtained in the mesh optimization step of this method. How ever, several bottlenecks may limit the parallelism. We provide some hypotheses about the factors that cause more parallel overhead. The relative number of elements, that are located at the interfaces of the sub-domains of the object, is one of the more important aspects for the e ciency of the parallel mesh optimization.Ministerio de Econom ía y Competitividad del Gobierno de Españ

Construction of polynomial spline spaces over quadtree and octree T-meshes for its application in isogeometric analysis

[EN]We present a new strategy for construction spline spaces over hierarchical T-meshes with quad- and octree subdivision scheme.MINECO y FEDER; CONACYT-SENER Project, Fondo Sectorial, contract: 16372

Wind Ensemble Forecasting Using Differential Evolution

[en]In this work we propose to apply ensemble methods to a local scale adaptive wind forecasting model

Optimisation technique for improving wind downscaling results by estimating roughness parameters

[EN]The characterisation of the aerodynamic roughness length (z0) and the displacement height (d) is critical when modelling the wind field using the log vertical profile. It is known that the values of these parameters depend on land coverage and weather conditions. Thus, many authors have studied their relationship, providing typical values for each land cover. In this paper, we have performed a comprehensive literature review to collect the intervals of z0 and d values for each land coverage. Using these intervals, we estimate their values using an optimisation technique that improves the results of a downscaling wind model. The downscaling model is a 3D adaptive, mass-consistent finite element model (Wind3D) that takes values from the HARMONIE-AROME or ECMWF mesoscale numerical weather prediction models. The optimisation is carried out by a memetic algorithm that combines the Differential Evolution method, a rebirth operator and the L-BFGS-B algorithm. The fitness function to be minimised is the root mean square error (RMSE) against observed wind data. This fast procedure allows updating the aerodynamic parameters for any weather condition. Numerical experiments have been carried out to show the performance of the methodology.Ministerio de Economía y Competitividad del Gobierno de Españ

A High Resolution DiagnosticWind Model. Application to Downscaling Mesoscale Model Results for Wind Forecasting

[EN]A mass consistent wind model is improved by introducing three items: the new 3-D mesh generator MECCANO applied to complex terrains, the current atmospheric stability definition by Zilitinkevich including new wind profiles, and a specific preconditioner for the linear systems arising in a wind model.Secretaría de Estado de Investigación, Desarrollo e Innovación del Ministerio de Economía y Competitividad del Gobierno de España; Fondos FEDE

Analysis of several objective functions for optimization of hexahedral meshes

Ministerio de Educación, Cultura y Deporte MINECO; FEDE

Strategies for optimization of hexahedral meshes and their comparative study

In this work, we study several strategies based on different objective functions for optimization of hexahedral meshes. We consider two approaches to construct objective functions. The first one is based on the decomposition of a hexahedron into tetrahedra. The second one is derived from the Jacobian matrix of the trilinear mapping between the reference and physical hexahedral element. A detailed description of all proposed strategies is given in the present work. Some computational experiments have been developed to test and compare the untangling capabilities of the considered objective functions. In the experiments, a sample of highly distorted hexahedral elements is optimized with the proposed objective functions, and the rate of success of each function is obtained. The results of these experiments are presented and analyzed.Secretaría de Estado de Universidades e Investigación del Ministerio de Economía y Competitividad del Gobierno de España; Programa de FPU del Ministerio de Educación, Cultura y Deporte; Programa de FPI propio de la ULPGC; Fondos FEDE

Spline parameterization method for 2D and 3D geometries based on T-mesh optimization

[EN]We present a method to obtain high quality spline parameterization of 2D and 3D geometries for their use in isogeometric analysis. As input data, the proposed method demands a boundary representation of the domain, and it constructs automatically a spline transformation between the physical and parametric domains. Parameterization of the interior of the object is obtained by deforming isomorphically an adapted parametric T-mesh onto the physical domain by applying a T-mesh untangling and smoothing procedure, which is the key of the method. Mesh optimization is based on the mean ratio shape quality measure. The spline representation of the geometry is calculated by imposing interpolation conditions using the data provided by one-to-one correspondence between the meshes of the parametric and physical domains. We give a detailed description of the proposed technique and show some examples. Also, we present some examples of the application of isogeometric analysis in geometries parameterized with our method.Secretaría de Estado de Universidades e Investigación del Ministerio de Economía y Competitividad del Gobierno de España y fondos FEDER; Programa de FPU 12/00202 del Ministerio de Educación, Cultura y Deporte; Programa de FPI propio de la Universidad de Las Palmas de Gran Canari

Solar Radiation Modelling and Forecasting

[EN]In this paper, an adaptive solar radiation numerical model for complex terrains is described.Secretaría de Estado de Investigación, Desarrollo e Innovación del Ministerio de Economía y Competitividad del Gobierno de España; Fondos FEDER