Solución numérica del problema de transmisión de calor con cambio de fase

Este trabajo resume el estado del arte de la solución numérica de los problemas de transmisión de calor con cambio de fase. Su objetivo consiste en presentar algoritmos en función de su capacidad de encarar problemas ingenieriles, dejando de lado los aspectos teóricos referidos a la convergencia de la solución numérica a-la solución matemática clásica del problema. Se detallan las ventajas y desventajas de los diferentes esquemas para que se pueda efectuar la selección del método más conveniente para un problema determinado. Asimismo se indican cuáles son las tendencias de investigación actuales y las posibilidades futuras en el área. Se incluye una serie de ejemplos numéricos para remarcar los aspectos destacables de los métodos tratados en el trabajo.Peer Reviewe

A portable OpenCL-based unstructured edge-based Finite Element Navier-Stokes solver on graphics hardware

The rise of GPUs in modern high-performance systems increases the interest in porting portion of codes to such hardware. The current paper aims to explore the performance of a portable state-of-the-art FE solver on GPU accelerators. Performance evaluation is done by comparing with an existing highly-optimized OpenMP version of the solver. Code portability is ensured by writing the program using the OpenCL 1.1 specifications, while performance portability is sought through an optimization step performed at the beginning of the calculations to find out the optimal parameter set for the solver. The results show that the new implementation can be several times faster than the OpenMP version.Preprin

Modelización del flujo invíscido alrededor de la pala de un aerogenerador mediante el método de los paneles

Se describe la formulación de un modelo computacional para determinar, bajo condiciones invíscidas, el flujo tridimensional alrededor de la pala de una turbina eólica de eje horizontal. Dicho modelo se basa en la representación mediante paneles de una pala rígida, delgada, torsionada y de envergadura finita. A estos paneles se asocian hilos vorticosos rectos, que conforman el sistema ligado a la pala, y un sistema de hilos vorticosos libres, que presentan trayectorias helicoidales de radios no constantes, que determinan una estela de configuración fija. Las velocidades inducidas por el sistema vorticoso completo son calculadas por la aplicación de la ley de Biot-Savart. Se presenta la metodología seguida para el cálculo de las distribuciones de circulación, velocidades inducidas y resultantes y cargas aerodinámicas a lo largo de la envergadura y cuerda de una pala de geometría definida, bajo una determinada condición de viento y rotación uniformes, sin la consideración de los efectos de interferencia.This work describes the formulation of a computational model to detemine, under inviscid conditions, the tri-dimensional flow field around the blade of an horizontal-axis wind turbine. The model is based upon a panel representation of a rigid, thin and twisted blade of finite span.The distribution of circulation is originated by a system of straight bound vortices associated to the blade and a system of free vortex filaments, having helical paths with non-constant radii, that generates a prescribed fixed wake. The velocities induced by that vortex system are calculated by the Biot-Savart law. The methodology followed in order to calculate the span and chordwise distributions of circulation, induced velocities and aerodynamic loads is presented for a blade whose geometry and working conditions are defined, without considering the interference effects.Peer Reviewe

A finite point method for three-dimensional compressible flow

Preprin

Forma simétrica de la condición de contorno absorbente DNL para el problema de la resistencia de ola en barcos

En la ref.' hemos presentado un esquema numérico basado en elementos finitos centrados con condición de contorno absorbente (la cual llamamos DNL, por Discrete Yon-Local) para el problema de la resistencia de ola en barcos. Al no agregar viscosidades numéricas este método da curvas de resistencia en función del Froude mejor definidas y posibilita el cálculo de la resistencia por el balance de flujo de momento a la salida. Sin embargo, debido a la naturaleza de la condición absorbente, el sistema resultante es no simétrico y en principio el sistema lineal resultante presenta ciertas dificultades para la factorización. En este trabajo se describe un método por el cual sólo es necesario factorizar una matriz simétrica y con el mismo ancho de banda que una matriz de elementos finitos típica, con el consecuente ahorro de memoria central (RAM).Peer Reviewe

Onninen Oy:n yötoimitusten kehittäminen

Tämä opinnäytetyö on tehty Onninen Oy:n toimeksiannon pohjalta. Opinnäytetyön aiheena on Onninen Oy:n yötoimitusten kehittäminen. Onninen Oy on vuonna 1913 perustettu Lvi- ja sähkötarvikemyynnin tukkukauppaa harjoittava yhtiö, jolla on tällä hetkellä n. 3000 työntekijää yhteensä yhdeksässä eri maassa. Onninen Oy on tämän hetken markkinajohtaja Suomessa. Opinnäytetyön teoreettisena viitekehyksenä on käytetty logistiikka-alan kirjallisuutta, Onninen Oy:n omia materiaaleja, tehtyjä haastatteluita sekä sähköisiä lähteitä. Kehityssuunnitelman päämääränä on parantaa yöjakelun kehittämisen avulla Onninen Oy:n kilpailukykyä sekä tuoda samalla asiakkaille entistä enemmän kyseisen palvelun tuomaa lisäarvoa. Opinnäytetyön tavoitteena on vähentää yötoimituksissa tapahtuvia virheitä sekä luoda samalla selkeämmät pelisäännöt jokaiselle ketjun toimijalle. Samalla opinnäytetyössä on keskeistä huomioida yrityksessä vähän aikaa sitten käyttöön otettu toiminnanohjausjärjestelmä, SAP. Opinnäytetyön pohjana toimii jo valmiiksi toimivan yöjakelukonseptin kehittäminen sekä uudistaminen. Työn tärkeimpiä elementtejä ovat toimitusketjussa havaittujen puutteiden paikallistaminen sekä niiden pohjalta tehtyjen kehityssuunnitelmien toimivuuden seuraaminen. Tehtyjen toimenpiteiden jälkeen Onninen Oy:n yötoimitukset ovat paljon paremmassa tilanteessa entiseen verrattuna. Nykyään toimituspoikkeamia tulee vain harvakseltaan verrattuna aikaisempaan tilanteeseen.Developing night deliveries of Onninen Oy This thesis was commissioned by Onninen Oy. The purpose of this thesis is to develop Onninen Ltd’s night deliveries. Onninen Oy was established in 1913 and it practices wholesaling of HVAC and electronic products. Onninen Oy currently employs around 3000 people in nine countries and is currently the market leader in Finland. The thesis has used source material from logistics related literature to e-sources. Also Onninen Oy’s own materials and numerous interviews have been used as source material. The aim of development plan is to improve Onninen Oy’s competitiveness and to give the customers even more added value with the service. The main aim of the thesis is to reduce errors that occur during the night deliveries and also to make clearer rules to each chain actor. At the same time it is important to take into account the company’s quite recently introduced ERP, SAP. The purpose of the thesis is to improve and to reform the already functioning night time delivery concept. The key elements of the thesis are to locate the deficiencies of the chain and to follow how well the improvement plans will be working. The measures taken after Onninen Oy’s night-time deliveries are in much better situation compared to the past. Today, supply deviations will occur only rarely compared to the previous situation

Reduced order models for thermally coupled low Mach flows

In this paper we present a collection of techniques used to formulate a projection-based reduced order model (ROM) for zero Mach limit thermally coupled Navier–Stokes equations. The formulation derives from a standard proper orthogonal decomposition (POD) model reduction, and includes modifications to improve the drawbacks caused by the inherent non-linearity of the used Navier–Stokes equations: a hyper-ROM technique based on mesh coarsening; an implicit ROM subscales formulation based on a variational multi-scale (VMS) framework; and a Petrov–Galerkin projection necessary in the case of non-symmetric terms. At the end of the article, we test the proposed ROM formulation using 2D and 3D versions of the same example: a differentially heated cavity.Peer ReviewedPostprint (published version

A finite point method for adaptive three-dimensional compressible flow calculation

The Finite Point Method (FPM) is a meshless technique which is based on both, a Weighted Least-Squares numerical approximation on local clouds of points and a collocation technique which allows obtaining the discrete system of equations. The research work we present is part of a major investigation into the capabilities of the FPM to deal with threedimensional applications concerning real compressible fluid flow problems. In the first part of this work, the upwind biased scheme employed for solving the flow equations is described. Secondly, with the aim of exploiting meshless capabilities, an h-adaptive methodology for two and three-dimensional compressible flow calculations is developed. This adaptive technique applies a solution-based indicator in order to identify local clouds where new points should be inserted in or existing points could be safely removed from the computational domain. The flow solver and the adaptive procedure have been evaluated and the results are highly encouraging. Several numerical examples are provided throughout the article in order to illustrate their performance.Preprin

Incompressible Lagrangian fluid flow with thermal coupling

In this monograph is presented a method for the solution of an incompressible viscous fluid flow with heat transfer and solidification usin a fully Lagrangian description on the motion. The originality of this method consists in assembling various concepts and techniques which appear naturally due to the Lagrangian formulation.Postprint (published version

A finite point method for compressible flow

This is the accepted version of the following article: [Löhner, R. , Sacco, C. , Oñate, E. and Idelsohn, S. (2002), A finite point method for compressible flow. Int. J. Numer. Meth. Engng., 53: 1765-1779. doi:10.1002/nme.334], which has been published in final form at https://onlinelibrary.wiley.com/doi/abs/10.1002/nme.334A weighted least squares finite point method for compressible flow is formulated. Starting from a global cloud of points, local clouds are constructed using a Delaunay technique with a series of tests for the quality of the resulting approximations. The approximation factors for the gradient and the Laplacian of the resulting local clouds are used to derive an edge-based solver that works with approximate Riemann solvers. The results obtained show accuracy comparable to equivalent mesh-based finite volume or finite element techniques, making the present finite point method competitive.Peer ReviewedPostprint (author's final draft