UVaFTLE: Lagrangian finite time Lyapunov exponent extraction for fluid dynamic applications

Producción CientíficaThe determination of Lagrangian Coherent Structures (LCS) is becoming very important in several disciplines, including cardiovascular engineering, aerodynam- ics, and geophysical fluid dynamics. From the computational point of view, the extraction of LCS consists of two main steps: The flowmap computation and the resolution of Finite Time Lyapunov Exponents (FTLE). In this work, we focus on the design, implementation, and parallelization of the FTLE resolution. We offer an in-depth analysis of this procedure, as well as an open source C implementation (UVaFTLE) parallelized using OpenMP directives to attain a fair parallel efficiency in shared-memory environments. We have also implemented CUDA kernels that allow UVaFTLE to leverage as many NVIDIA GPU devices as desired in order to reach the best parallel efficiency. For the sake of reproducibility and in order to con- tribute to open science, our code is publicly available through GitHub. Moreover, we also provide Docker containers to ease its usage.Ministerio de Economía, Industria y Competitividad, Consejo Asesor de Educación de Castilla y León y Programas del Fondo de Desarrollo (FEDER): Proyecto PCAS (TIN2017-88614-R) y Proyecto PROPHET-2 (VA226P20).Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación y “European Union NextGenerationEU/PRTR” : (MCIN/ AEI/10.13039/501100011033) - (grant TED2021-130367B-I00)Junta de Castilla y León (project VA182P20)Red Española de Supercomputación (RES) (projects IM-2022-2-0015 and IM-2022-3-0021)Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Experimental and numerical study of the influence of the plenum box on the airflow pattern generated by a swirl air diffuser

When CFD is employed to design a ventilation system, one of the most delicate aspects is the modeling of the diffuser. The designer has different choices, which range from simulating the detailed geometry of the diffuser, including the plenum box, to use special boundary conditions to reproduce the velocity profile in each slot of the diffuser. This study is carried out to examine the influence of the plenum box on the turbulent airflow pattern generated by a swirl air diffuser from the experimental and numerical points of view. First, we perform experiments to evaluate such influence. Then, these experiments are contrasted with two numerical approximations to the problem using the Fluent 6.3.26 commercial CFD software. We first perform a simulation of the complete diffuser geometry – including the plenum box – and later a simplified simulation of the diffuser, where the whole geometry is simplified to a plane in which the velocity components and the slots positioning are specified via a particular boundary condition. The main findings of this study reveal that the simplified simulation is good enough at close range, while in the remote flow field the differences between both approaches practically disappear. © 2018 Elsevier Inc.Project DPI2014-55357-C2-1-R from the Spanish National Government 2013–2016 R&D&I plan issued by the Ministry of Economy and Competiveness. This project is cofinanced by the European Regional Development Fund (ERDF)