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Projecte presentat al Concurs d'idees per a l'ordenació i urbanització del Vial-Balconada de la Vall Salina, CardonaSegon premiAward-winningPostprint (published version

Parallel Adaptive Mesh Refinement Simulation of the Flow Around a Square Cylinder at Re = 22000

AbstractIn this paper a parallel adaptive mesh refinement for LES simulation of turbulent flows is presented. The AMR scheme applies a cell- based refinement technique to get enough grid-resolution to solve the small scales structures, adapting the mesh according to physics- based refinement criteria. A flexible tree data structure is used to keeping track of the mesh adaptation and an edge-based data structure to save and search cell connectivity. The AMR framework is combined with parallel algorithms for partitioning and balancing of the computational mesh. Numerical results for turbulent flow around a square cylinder at Re = 22000 are compared to experimental data

Numerical simulation of roughness effects on the flow past a circular cylinder

In the present work large eddy simulations of the flow past a rough cylinder are performed at a Reynolds number of Re = 4.2 × 105 and an equivalent sand-grain surface roughness height ks = 0.02D. In order to determine the effects of the surface roughness on the boundary layer transition and as a consequence on the wake topology, results are compared to those of the smooth cylinder. It is shown that surface roughness triggers the transition to turbulence in the boundary layer, thus leading to an early separation caused by the increased drag and momentum deficit. Thus, the drag coefficient increases up to CD 1.122 (if compared to the smooth cylinder it should be about CD 0.3 - 0.5). The wake topology also changes and resembles more the subcritical wake observed for the smooth cylinder at lower Reynolds numbers than the expected critical wake at this Reynolds number.Peer ReviewedPostprint (author's final draft

Mediterranean rural landscapes: methodological guide for the implementation of a model of territorial governance

Guia metodològica de Bones Pràctiques de Paisatge en el marc del programa europeu INTEREG Modeland.Postprint (published version

Numerical analysis of conservative unstructured discretisations for low Mach flows

This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. https://authorservices.wiley.com/author-resources/Journal-Authors/licensing-and-open-access/open-access/self-archiving.htmlUnstructured meshes allow easily representing complex geometries and to refine in regions of interest without adding control volumes in unnecessary regions. However, numerical schemes used on unstructured grids have to be properly defined in order to minimise numerical errors. An assessment of a low-Mach algorithm for laminar and turbulent flows on unstructured meshes using collocated and staggered formulations is presented. For staggered formulations using cell centred velocity reconstructions the standard first-order method is shown to be inaccurate in low Mach flows on unstructured grids. A recently proposed least squares procedure for incompressible flows is extended to the low Mach regime and shown to significantly improve the behaviour of the algorithm. Regarding collocated discretisations, the odd-even pressure decoupling is handled through a kinetic energy conserving flux interpolation scheme. This approach is shown to efficiently handle variable-density flows. Besides, different face interpolations schemes for unstructured meshes are analysed. A kinetic energy preserving scheme is applied to the momentum equations, namely the Symmetry-Preserving (SP) scheme. Furthermore, a new approach to define the far-neighbouring nodes of the QUICK scheme is presented and analysed. The method is suitable for both structured and unstructured grids, either uniform or not. The proposed algorithm and the spatial schemes are assessed against a function reconstruction, a differentially heated cavity and a turbulent self-igniting diffusion flame. It is shown that the proposed algorithm accurately represents unsteady variable-density flows. Furthermore, the QUICK schemes shows close to second order behaviour on unstructured meshes and the SP is reliably used in all computations.Peer ReviewedPostprint (author's final draft

Direct numerical simulation of the turbulent natural convection flow in an open cavity of aspect ratio 4

In this paper, three-dimensional turbulent natural convection heat transfer in an open cavity with an isothermal wall facing the overture has been studied. The aspect ratio chosen for the cavity has been 4 to complement the studies by Trias et al. [1, 2] of closed cavities with the same aspect ratio. Direct numerical simulations (DNS) of the cavity are presented and analyzed. Rayleigh numbers up to Ra = 1012 has been considered.Peer ReviewedPostprint (published version

DNS of falling droplets in a vertical channel

© 2018 WIT PressThis paper presents Direct Numerical Simulation (DNS) of the falling motion of single and multiple deformable drops in a vertical channel. A systematic study of the wall effect on the motion of single drop is performed for Eötvös number (0.5=Eo=5), Morton number (10-3=M=10-8), and confinement ratio CR = 2. Second, the gravity-driven motion of multiple drops and their interactions are studied in a periodic vertical channel for CR = 4. These simulations are performed using a multiple marker level-set methodology, integrated in a finite-volume framework on a collocated unstructured grid. Each droplet is described by a level-set function, which allows capturing multiple interfaces in the same control volume, avoiding the numerical merging of the droplets. Numerical algorithms for fluid motion and interface capturing have been developed in the context of the finite-volume and level-set methodology, surface tension is modeled by means of the continuous surface force approach, and the pressure-velocity coupling is solved using a fractional-step projection method. DNS of single drop shows that they migrate to the symmetry axis of the channel when the Reynolds number is low, following a monotonic approach or damped oscillations according to the dimensionless parameters. If Eötvös number increases, stronger oscillations around the symmetry axis are observed. Simulations of multiple drops show that the collision of two drops follows the drafting-kissing tumbling (DKT) phenomenon. Deformable drops do not collide with the wall, whereas DKT phenomenon in the droplet swarm leads to the formation of groups which move through the center of the channel.Peer ReviewedPostprint (published version

A GPU Accelerated Framework for Partitioned Solution of Fluid-Structure Interaction Problems

We present a GPU-accelerated solver for the partitioned solution of fluid-structure interaction (FSI) problems. Independent scalable fluid and structure solvers are coupled by a library which handles the inter-code data communication, mapping and equation coupling. A coupling strategy is incorporated which allows accelerating expensive components of the coupled framework by offloading them to GPUs. To prove the efficiency of the proposed coupling strategy in conjunction with the offloading scheme, we present a numerical performance analysis for a complex test case in the filed of biomedical engineering. The numerical experiments demonstrate an excellent speed-up in the accelerated kernels (up to 133 times) which results in 6 to 8 times faster overall simulations. In addition, we observed a very good reduction in total simulation time by increasing the exploited compute nodes up to 8 (complete machine capacity).We thank the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for supporting this work by funding - EXC2075 – 390740016 under Germany’s Excellence Strategy. We acknowledge the support by the Stuttgart Center for Simulation Science (SimTech). This work was also financially supported by • priority program 1648 - Software for Exascale Computing 214 (ExaFSA - Exascale Simulation of Fluid-Structure-Acoustics Interactions) of the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), • Ministerio de Economía y Competitividad, Secretaría de Estado de Investigacion, Desarrollo e ´ Innovacion, Spain (ENE2017-88697-R). ´ The performance measurements were carried out on the Vulcan cluster at the High-Performance Computing Center Stuttgart (HLRS). The authors wish to thank HLRS for compute time and technical support.Peer ReviewedPostprint (published version

Mediterranean rural landscapes: Guide of best landescape practices and pilot actions

Postprint (published version

Advanced CFD&HT numerical modeling of solar tower receivers

This paper presents an advanced methodology for the detailed modeling of the heat transfer and fluid dynamics phenomena in solar tower receivers. It has been carried out in the framework of a more ambitious enterprise which aims at modeling all the complex heat transfer and fluid dynamics phenomena present in central solar receivers. The global model is composed of 4 sub-models (heat conduction, two-phase flow, thermal radiation and natural convection) which are described.Peer ReviewedPostprint (published version