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  • Numerical investigation of particle-fluid interaction system based on discrete element method

     Zhang, Hao
    Universitat Politècnica de Catalunya
    Theses

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    Esta tesis se centra en la investigación numérica de sistemas partícula-líquido basado en la técnica Discrete Element Method (DEM). La tesis consta de tres partes, en cada una de las cuales se ha acoplado el método DEM con diferentes esquemas/solucionadores en la fase fluida. En la primera parte, hemos acoplado los métodos DEM con Direct Numerical Simulation (DNS) para estudiar casos de "particle-laden turbulent flow". Se investigó numéricamente el efecto de las colisiones en el comportamiento de las partículas en el flujo turbulento completamente desarrollado en un conducto cuadrado recto. Tres tamaños de partículas se consideraron con diámetros de 50, 100 y 500 micrometros. En primer lugar, el transporte de partículas por el flujo turbulento se estudió en la ausencia del efecto gravitacional. Entonces, la deposición de partículas se estudió bajo el efecto de la fuerza de gravedad normal a la pared, en el que se discutieron la influencia de la tasa de colisiones en re-suspensión de las partículas y la fase final de la distribución de partículas en el suelo del conducto, respectivamente. En la segunda parte, se ha acoplado los métodos DEM con Lattice Boltzmann Method (LBM) para estudiar la sedimentación de partículas en flujo laminar newtoniano. Un nuevo metodo combinado LBM-IBM-DEM se presentó y ha sido aplicado para modelar la sedimentación de dos partículas circulares bi-dimensionales en flujos Newtonianos incompresibles. Se estudiaron casos de sedimentación en una cavidad de una sola esfera, y sedimentación de dos partículas en un canal, las características de la velocidad de la partícula durante la sedimentación y cerca de la base fueron también examinados. En el último caso, un ejemplo numérico de sedimentación de 504 partículas fue finalmente presentado para demostrar la capacidad del método combinado. Además, se ha presentado un método "Particulate Immersed Boundary Method" (PIBM) para la simulación de flujos multifásicos partícula-fluido y ha sido evaluado en dos y tres dimensiones. En comparación con el método IBM convencional, se puede esperar con el mismo número de partículas y de malla un SpeedUp docenas de veces superior en la simulación bidimensional y cientos de veces en la simulación en tres dimensiones. Se llevaron a cabo simulaciones numéricas de la sedimentación de partículas en los flujos newtonianos basados en una combinación LBM - PIBM - DEM, mostrando que el PIBM podría capturar las características de los flujos de partículas en el líquido y fue en efecto un esquema prometedor para la solución de problemas de interacción fluido-partícula. En la última parte, se ha acoplado el método DEM con las ecuaciones promediadas de Navier-Stokes (NS) para estudiar el transporte de partículas y el proceso de desgaste en la pared de una tubería. Se utilizó un caso de transporte neumático para demostrar la capacidad del modelo acoplado. Entonces se simuló el proceso de bombeo de hormigón, de donde se obtuvo la presión hidráulica y la distribución de la velocidad de la fase fluida. Se monitoreó la frecuencia de impacto de las partículas en la tubería doblada, se propuso un nuevo modelo de intensidad de colisión promediado en tiempo para investigar el proceso de desgaste del codo basado en la fuerza de impacto. Se predijo la ubicación del daño máximo desgaste por erosión en el codo. Además, se examinaron las influencias de la velocidad de pulpa, la orientación y el ángulo de curvatura del codo en la ubicación del punto de punción.

  • Centre Tecnològic de Transferència de Calor

     Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Trias Miquel, Francesc Xavier; Colomer Rey, Guillem; Capdevila Paramio, Roser; Ablanque Mejia, Nicolas; Lehmkuhl Barba, Oriol; Carmona Muñoz, Angel; Sadurni Caballol, Alexandre; Kizildag, Deniz; Giraldez Garcia, Hector; Chiva Segura, Jorge; Baez Vidal, Aleix; Lopez Mas, Joan; Farnos Baulenas, Joan; Torras Ortiz, Santiago; Balcazar Arciniega, Nestor Vinicio; Martinez Valdivieso, Daniel; Jofre Cruanyes, Lluís; Calafell Sandiumenge, Joan; Estruch Perez, Olga; Muela Castro, Jordi; Ventosa Molina, Jordi; Aizpurua Udabe, Imanol; Schillaci, Eugenio; Favre, Federico; Zhang, Hao; Aljure Osorio, David E.; Morales Ruiz, Sergio; Borrell Pol, Ricard; Galione Klot, Pedro Andres; Dabbagh, Firas; Oyarzun Altamirano, Guillermo; Gorobets, Andrei; Oliva Llena, Asensio
    Competitive project

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  • Progress on eddy-viscosity models for LES: new differential operators and discretization methods

     Trias Miquel, Francesc Xavier; Verstappen, Roel; Gorobets, Andrei; Oliva Llena, Asensio
    European Turbulence Conference
    Presentation's date: 2013-09-04
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Reynolds numbers. Therefore, dynamically less complex mathematical formulations are necessary for coarse-grain simulations. Eddy-viscosity models for Large-Eddy Simulation (LES) is an example thereof: they rely on differential operators that should be able to capture well different flow configurations (laminar and 2D flows, near-wall behavior, transitional regime...). In the present work, several differential operators are derived from the criterion that vortex-stretching mechanism must stop at the smallest grid scale. Moreover, since the discretization errors may play a n important role a novel approach to discretize the viscous term with spatially varying eddy-viscosity is used. It is based on basic operators; therefore, the implementation is straightforward even for staggered formulations.

  • Blending regularization and large-eddy simulation. From homogeneous isotropic turbulence to wind farm boundary layers

     Folch Flórez, David; Trias Miquel, Francesc Xavier; Gorobets, Andrei; Oliva Llena, Asensio
    European Turbulence Conference
    Presentation's date: 2013-08
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations form an excellent mathematical model for turbulent flows. However, direct simulations at high Reynolds numbers are not feasible because the convective term produces far too many relevant scales of motion. Therefore, in the foreseeable future numerical simulations of turbulent flows will have to resort to models of the small scales. Large-eddy simulation (LES) and regularization models are examples thereof. In the present work, we propose to combine both approaches. Restoring the Galilean invariance of the regularization method results into an additional hyperviscosity term. This approach provides a natural blending between regularization and LES. The performance of these recent improvements will be assessed through application to homogeneous isotropic turbulence, a turbulent channel flow and a wind-farm turbulent boundary layer.

  • Máquina de absorción refrigerada por aire

     Oliva Llena, Asensio; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Alba Queipo, Ramiro; Ordoño Martinez, Manuel Miguel; Farnos Baulenas, Joan
    Date of request: 2013-06-14
    Invention patent

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  • An OpenCL-based parallel CFD code for simulations on hybrid systems with massively-parallel accelerators

     Gorobets, Andrei; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 81-86
    Presentation's date: 2013-05-23
    Presentation of work at congresses

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  • New differential operators and discretization methods for eddy-viscosity models for LES

     Trias Miquel, Francesc Xavier; Gorobets, Andrei; Zhang, Hao; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 179-184
    Presentation's date: 2013-05-22
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, at- tempts at performing direct numerical simulations (DNS) are limited to relatively low-Reynolds numbers. Therefore, dynamically less complex mathematical formulations are necessary for coarse-grain simulations. Eddy-viscosity models for Large-Eddy Sim- ulation (LES) is an example thereof: they rely on differential operators that should be able to capture well different flow config- urations (laminar and 2D flows, near-wall behavior, transitional regime...). In the present work, several differential operators are derived from the criterion that vortex-stretching mechanism must stop at the smallest grid scale. Moreover, since the discretization errors may play an important role a novel approach to discretize the viscous term with spatially varying eddy-viscosity is used. It is based on basic operators; therefore, the implementation is straightforward even for staggered formulations. The performance of the proposed models will be assessed by means of direct comparison to DNS reference results.

  • Direct and large-eddy simulation of non-oberbeck-boussinesq effects in a turbulent differentially heated cavity

     Kizildag, Deniz; Trias Miquel, Francesc Xavier; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    ERCOFTAC Workshop on Direct and Large-Eddy Simulation
    Presentation's date: 2013-04-04
    Presentation of work at congresses

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  • Acumulador de energía térmica en base a materiales de cambio de fase sólido-líquido y método de fabricación de la unidad

     Oliva Llena, Asensio; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Alba Queipo, Ramiro; Ordoño Martinez, Manuel Miguel; Morales Ruiz, Sergio
    Date of request: 2013-03-01
    Invention patent

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  • Sistema de almacenamiento de energía térmica combinando material sólido de calor sensible y material de cambio de fase

     Oliva Llena, Asensio; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Galione Klot, Pedro Andres
    Date of request: 2012-12-27
    Invention patent

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    Un sistema para el almacenamiento y recuperación de energía térmica empleando como medio al menos un material de cambio de fase (sólido-líquido) y un material sólido de calor sensible que se encargan de almacenar/recuperar el calor obtenido desde una fuente externa en forma de calor sensible y calor latente de cambio de fase. Dichos materiales están debidamente contenidos en un único tanque, en cuyo interior existen al menos dos zonas, cada una conteniendo un material diferente, y diferenciadas por el rango de temperaturas a las que son sometidas. La configuración más usada consiste en tres diferentes zonas configuradas al interior del tanque: zona caliente, en la parte superior del tanque, donde un material de cambio de fase encapsulado caracterizado por una temperatura de fusión alta está encerrado; zona fría, ubicada en la parte inferior, donde un material de cambio de fase con baja temperatura de fusión está colocado; y una zona media, que contiene un material sólido de calor sensible.

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    Spectrally-consistent regularization modeling of turbulent natural convection flows  Open access

     Trias Miquel, Francesc Xavier; Verstappen, R.W.C.P.; Oliva Llena, Asensio; Gorobets, Andrei
    European Thermal Sciences Conference
    p. vol.395--
    DOI: 10.1088/1742-6596/395/1/012123
    Presentation's date: 2012-09-05
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Reynolds numbers because of the almost numberless small scales produced by the non-linear convective term. Alternatively, a dynamically less complex formulation is proposed here. Namely, regularizations of the Navier-Stokes equations that preserve the symmetry and conservation properties exactly. To do so, both convective and diffusive terms are altered in the same vein. In this way, the convective production of small scales is effectively restrained whereas the modified diffusive term introduces a hyperviscosity effect and consequently enhances the destruction of small scales. In practice, the only additional ingredient is a self-adjoint linear filter whose local filter length is determined from the requirement that vortex-stretching must stop at the smallest grid scale. In the present work, the performance of the above-mentioned recent improvements is assessed through application to turbulent natural convection flows by means of comparison with DNS reference data.

    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Reynolds numbers because of the almost numberless small scales produced by the non-linear convective term. Alternatively, a dynamically less complex formulation is proposed here. Namely, regularizations of the Navier-Stokes equations that preserve the symmetry and conservation properties exactly. To do so, both convective and diffusive terms are altered in the same vein. In this way, the convective production of small scales is effectively restrained whereas the modified diffusive term introduces a hyperviscosity effect and consequently enhances the destruction of small scales. In practice, the only additional ingredient is a self-adjoint linear filter whose local filter length is determined from the requirement that vortex-stretching must stop at the smallest grid scale. In the present work, the performance of the above-mentioned recent improvements is assessed through application to turbulent natural convection flows by means of comparison with DNS reference data.

  • An eulerian-lagrangian modeling of fluidized bed

     Zhang, Hao; Yuan-Qiang, Tan; Dong-Min, Yang; Trias Miquel, Francesc Xavier; Sheng, Yong; Oliva Llena, Asensio
    National Conference on Computational Mechanics of Granular Materials
    p. 659-663
    Presentation's date: 2012-09-17
    Presentation of work at congresses

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    Spectrally-consistent regularization modeling of wind farm boundary layers  Open access

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Folch, David; Oliva Llena, Asensio
    Conference on Modelling Fluid Flow
    p. 96-103
    Presentation's date: 2012-09-06
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Reynolds numbers because of the almost numberless small scales produced by the non-linear convective term. Alternatively, a dynamically less complex formulation is proposed here. Namely, regularizations of the Navier-Stokes equations that preserve the symmetry and conservation properties exactly. To do so, both convective and diffusive term are altered in the same vein. In this way, the convective production of small scales is effectively restrained whereas the modified diffusive term introduces a hyperviscosity effect and consequently enhances the destruction of small scales. In practise, the only additional ingredient is a self-adjoint linear filter whose local filter length is determined from the requirement that vortex-stretching must stop at the smallest grid scale. In the present work, the performance of the above-mentioned recent improvements is assessed through application to homogeneous isotropic turbulence, a turbulent channel flow and a turbulent boundary layer. As a final application, regularization modelling will be applied for large-scale numerical simulation of the atmospheric boundary layer through wind farms.

  • Spectrally-consistent regularization modeling at very high Rayleigh numbers

     Trias Miquel, Francesc Xavier; Verstappen, R.W.C.P.; Gorobets, Andrei; Oliva Llena, Asensio
    International Symposium on Turbulence, Heat and Mass Transfer
    Presentation's date: 2012-09-19
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Rayleigh numbers because of the almost numberless small scales produced by the non-linear convective term. Alternatively, a dynamically less complex formulation is proposed here. Namely, regularizations of the Navier-Stokes equations that preserve the symmetry and conservation properties exactly. To do so, both convective and diffusive term are altered in the same vein. In this way, the convective production of small scales is effectively restrained whereas the modified diffusive term introduces a hyperviscosity effect and consequently enhances the destruction of small scales. In practice, the only additional ingredient is a selfadjoint linear filter whose local filter length is determined from the requirement that vortex-stretching must stop at the smallest grid scale. The performance of the novel regularization modeling approach is assessed through application to turbulent natural convection flows at very high Rayleigh numbers

  • Eulerian-Lagrangian modeling of fluidized bed

     Tan, Y; Zhang, Hao; Yang, D; Trias Miquel, Francesc Xavier; Sheng, Y.; Oliva Llena, Asensio
    National Conference on Computational Mechanics of Granular Materials
    Presentation's date: 2012-06-14
    Presentation of work at congresses

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  • Spectrally-consistent regularization modeling of turbulence and its connections with LES

     Trias Miquel, Francesc Xavier
    Connections Between Regularized and Large-Eddy Simulation Methods for Turbulence
    Presentation's date: 2012-05-13
    Presentation of work at congresses

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  • DNS and regularization modeling of a turbulent flow through a square duct up to Re _tau = 1200

     Trias Miquel, Francesc Xavier; Gorobets, Andrei; Zhang, Hao; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 48-49
    Presentation's date: 2012-05-20
    Presentation of work at congresses

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  • A parallel OpenCL-based solver for large-scale DNS of incompressible flows on heterogenous systems

     Trias Miquel, Francesc Xavier; Gorobets, Andrei; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 22-23
    Presentation's date: 2012-05-20
    Presentation of work at congresses

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  • Towards the regularization modeling of wind farm boundary layers

     Trias Miquel, Francesc Xavier; Folch, David; Gorobets, Andrey; Oliva Llena, Asensio
    EUROMECH Colloquium
    Presentation's date: 2012-02-15
    Presentation of work at congresses

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  • Turbulent natural convection in a differentially heated cavity of aspect ratio 5 filled with non-participating and participating grey media

     Capdevila Paramio, Roser; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Perez Segarra, Carlos David; Colomer, G.
    European Turbulence Conference
    p. 1-10
    DOI: 10.1088/1742-6596/318/4/042048
    Presentation's date: 2011-12-22
    Presentation of work at congresses

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    In the present work, turbulent natural convection in a tall differentially heated cavity of aspect ratio 5:1, filled with air (Pr = 0.7) under a Rayleigh number based on the height of 4.5 centerdot 1010, is studied numerically. Two different situations have been analysed. In the first one, the cavity is filled with a transparent medium. In the second one, the cavity contains a grey participating gas. The turbulent flow is described by means of Large Eddy Simulation (LES) using symmetry-preserving discretizations. Simulations are compared with experimental data available in the literature and with Direct Numerical Simulations (DNS). Surface and gas radiation have been simulated using the Discrete Ordinates Method (DOM). The influence of radiation on fluid flow behaviour has also been analysed.

  • Numerical simulation of particle-laden turbulent flow using discrete element method

     Zhang, Hou; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
    International Conference on Particle-based Methods
    p. 1
    Presentation's date: 2011-10-26
    Presentation of work at congresses

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  • Symmetry-preserving regularization of wall-bounded turbulent flows

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Verstappen, R.W.C.P.; Oliva Llena, Asensio
    European Turbulence Conference
    p. 1-10
    DOI: 10.1088/1742-6596/318/4/042060
    Presentation's date: 2011-09-12
    Presentation of work at congresses

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    The incompressible Navier-Stokes equations constitute an excellent mathematical modelization of turbulence. Unfortunately, attempts at performing direct simulations are limited to relatively low-Reynolds numbers because of the almost numberless small scales produced by the non-linear convective term. Alternatively, a dynamically less complex formulation is proposed here. Namely, regularizations of the Navier-Stokes equations that preserve the symmetry and conservation properties exactly. To do so, both convective and diffusive term are altered in the same vein. In this way, the convective production of small scales is effectively restrained whereas the modified diffusive term introduces an hyper-viscosity effect and consequently enhances the destruction of small scales. In practice, the only additional ingredient is a self-adjoint linear filter whose local filter length is determined from the requirement that vortex-stretching must stop at the smallest grid scale. To do so, a new criterion based on the invariants of the local strain tensor is proposed here. Altogether, the proposed method constitutes a parameter-free turbulence model.

  • Turbulent differentially heated cavity of aspect ratio 5 : direct numerical simulation and regularization modeling

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Oliva Llena, Asensio
    International Conference on Computational Heat and Mass Transfer
    p. 1-8
    Presentation's date: 2011-07-07
    Presentation of work at congresses

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    This work is devoted to the study of turbulent natural convection flows in differentially heated cavities. The adopted configuration corresponds to an air-filled (Pr = 0.7) cavity of aspect ratio 5 and Rayleigh number Ra = 4.5 × 1010 (based on the cavity height). Firstly, a complete direct numerical simulation (DNS) has been performed. Then, the DNS results have been used as reference solution to assess the performance of symmetry-preserving regularization as a simulation shortcut: a novel class of regularization that restrain the convective production of small scales of motion in an unconditionally stable manner. In this way, the new set of equations are dynamically less complex than the original Navier-Stokes equations, and therefore more amenable to be numerically solved. Time-averaged DNS results have revealed that the transition of the vertical boundary layer occurs at more downstream positions than those observed in the experiments.

  • Hybrid MPI+OpenMP parallelization of a Navier-Stokes solver for large-scale DNS

     Gorobets, Andrey; Trias Miquel, Francesc Xavier; Borrell Pol, Ricard; Soria Guerrero, Manel; Oliva Llena, Asensio
    International Conference on Computational Heat and Mass Transfer
    p. 1-5
    Presentation's date: 2011-07-07
    Presentation of work at congresses

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    This work presents a parallel Navier-Stokes solver for the large-scale direct numerical simulation (DNS) of incompressible flows with one periodic direction. It is based on a scalable Poisson solver that combines an FFT diagonalization with a preconditioned conjugate gradient (PCG) method and a direct Schurcomplement based method. Modern architectures of supercomputers with multi-core nodes motivate the use of a two-level hybrid MPI+OpenMP parallelization. The use of the more complex two-level approach has allowed to significantly extend the number of CPUs the solver can efficiently use. Here, the solver has been successfully tested on up to 12800 CPU cores for meshes with up to 109 grid points. However, estimations based on presented results show that more than 50000 CPU cores can potentially be exploited.

  • Numerical simulations of turbulent natural convection coupled and uncoupled with radiation

     Capdevila Paramio, Roser; Lehmkuhl Barba, Oriol; Colomer Rey, Guillem; Trias Miquel, Francesc Xavier; Perez Segarra, Carlos David
    International Conference on Computational Heat and Mass Transfer
    p. 1-8
    Presentation's date: 2011-07-18
    Presentation of work at congresses

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    In the present work, turbulent natural convection in a tall differentially heated cavity of aspect ratio 5:1, filled with air (Pr = 0.7) under a Rayleigh number based on the height of 4.5 · 1010, is studied numerically. Two different situations have been analysed. In the first one, the cavity is filled with a transparent medium. In the second one, the cavity contains a grey participating gas. The turbulent flow is described by means of Large Eddy Simulation (LES) using symmetry-preserving discretizations. Simulations are compared with experimental data available in the literature and with Direct Numerical Simulations (DNS). Surface and gas radiation have been simulated using the Discrete Ordinates Method (DOM). The influence of radiation on fluid flow behaviour has also been analysed.

  • Effect of mesh partition on the scalability of the parallel solution of the radiative transfer equation

     Colomer Rey, Guillem; Borrell Pol, Ricard; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
    International Conference on Computational Heat and Mass Transfer
    p. 1-8
    Presentation's date: 2011-07-18
    Presentation of work at congresses

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    The radiative transfer equation is solved in parallel using spatial domain decomposition. The effect of several kinds of mesh partitioning strategies is analyzed in this work. Geometries discretized with both structured and unstructured meshes have been considered, and significant differences in performance have been observed in both cases.

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    Hybrid MPI+OpenMP parallelization of an FFT-based 3D Poisson solver that can reach 100000 CPU cores  Open access

     Gorobets, Andrey; Trias Miquel, Francesc Xavier; Borrell Pol, Ricard; Soria Guerrero, Manel; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 1-5
    Presentation's date: 2011-05-07
    Presentation of work at congresses

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    This work is devoted to the development of efficient parallel algorithms for the direct numerical simulation (DNS) of incompressible flows on modern supercomputers. A Poisson solver for problems with one uniform periodic direction is presented here. It is extended with a two-level hybrid MPI+OpenMP parallelization. Advantages and implementation details for the additional OpenMP parallelization are presented and discussed. This upgrade has allowed to significantly extend the range of efficient scalability. Here, the solver has been tested up to 12800 CPU cores for meshes with up to 10 9 nodes. However, estimations based on the presented results show that this range can be potentially stretched beyond 10 5 cores.

    Postprint (author’s final draft)

  • Numerical simulation of turbulence at lower costs: regularization modeling

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Soria Guerrero, Manel; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 1-5
    Presentation's date: 2011-05-07
    Presentation of work at congresses

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    Parallelization of a DEM/CFD code for the numerical simulation of particle-laden turbulent flows  Open access

     Zhang, Hao; Trias Miquel, Francesc Xavier; Tan, Y.Q.; Sheng, Y.; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 1-5
    Presentation's date: 2011-05-07
    Presentation of work at congresses

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    The interaction between a turbulent fluid flow and particle motion is investigated numerically. A complete direct numerical simulation (DNS) is carried out to solve the governing equations of the fluid phase, to investigate the behavior of inter-particle collision and its effects on particle dispersion, the discrete element method (DEM) is employed to calculate the particle motion.The parallelization strategy of the DNS part is based on a domain decomposition method and uses a hybrid MPI+OpenMP approach. On the other hand, the OpenMP is used for the parallelization of DEM: the total number of particles to be tracked are equally distributed among processors. Finally, the method is tested for a turbulent flow through a square duct.

    Postprint (author’s final draft)

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    FFT-based Poisson Solver for large scale numerical simulations of incompressible flows  Open access

     Borrell Pol, Ricard; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Oyarzun Altamirano, Guillermo; Oliva Llena, Asensio
    International Conference on Parallel Computational Fluid Dynamics
    p. 1-5
    Presentation's date: 2011-05-16
    Presentation of work at congresses

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    In the context of time-accurate numerical simulation of incompressible flows, a Poisson equation needs to be solved at least once per time-step to project the velocity field onto a divergence-free space. Due to the non-local nature of its solution, this elliptic system is one of the most time consuming and difficult to parallelise parts of the code. In this paper, a parallel direct Poisson solver restricted to problems with one uniform periodic direction is presented. It is a combination of a Direct Schur-complement based Decomposition (DSD) and a Fourier diagonalisation. The latter decomposes the original system into a set of mutually independent 2D systems which are solved by means of the DSD algorithm. Since no restrictions are imposed in the non-periodic directions, the overall algorithm is well-suited for solving problems discretised on extruded 2D unstructured meshes. A new overall parallelisation strategy with respect to our earlier works is presented. This has allowed us to solve discrete Poisson equations with up to 109 grid points in less than half a second, using up to 8192 CPU cores of the MareNostrum Supercomputer.

    Postprint (author’s final draft)

  • DESARROLLO CODIGOS Y ALGORITMOS PARALELOS ALTA PRESTACIONES FINES DISEÑO OPTIMIZADO SISTEMAS Y EQUIPOS TERMICOS

     Perez Segarra, Carlos David; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Chiva Segura, Jorge; Gorobets, Andrey; Giraldez Garcia, Hector; Ventosa Molina, Jordi; Oliva Llena, Asensio
    Competitive project

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  • Turbulent flow in a differentially heated cavity: direct numérical simulation and regularization modeling

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Oliva Llena, Asensio; Verstappen, R.W.C.P.
    International Heat Transfer Conference
    p. 1-10
    Presentation's date: 2010-08-09
    Presentation of work at congresses

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    We consider regularizations of the convective term that preserve symmetry and conservation properties exactly. This yields a novel class of regularizations that restrain the convective production of small scales in an unconditionally stable manner Numerically, one of the most critical issues is the discrete filtering; properties required are, in general, not preserved by classical LES filters. Alternatively, here we propose to construct filters with the general form F = I + ΣMm =1 dm ˜Dm where ˜D is the discrete diffusive operator. Then, the coefficients, dm, follow from the requirement that, at the smallest grid scale kc, the damping effect to the wavevector-triple (kc, p,kc− p) interactions must be virtually independent of the p-th Fourier-mode. This allows an optimal control of the subtle balance between convection and diffusion to stop the vortex-stretching. Finally, the proposed method is tested for an air-filled differentially heated cavity of aspect ratio 4 by direct comparison with DNS reference results.

  • Regularization modeling of buoyancy-driven flows

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Oliva Llena, Asensio; Verstappen, R.W.C.P.
    ERCOFTAC Workshop on Direct and Large-Eddy Simulation
    p. 21-26
    DOI: 10.1007/978-94-007-2482-2_4
    Presentation's date: 2010-07-07
    Presentation of work at congresses

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  • Regularization modeling of wall-bounded turbulent flows

     Trias Miquel, Francesc Xavier; Gorobets, Andrey; Verstappen, R.W.C.P.; Oliva Llena, Asensio
    European Conference on Computational Fluid Dynamics
    p. 1-20
    Presentation's date: 2010-06-15
    Presentation of work at congresses

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    Since direct numerical simulations cannot be computed at high Reynolds numbers, a dynamically less complex formulation is sought. In the quest for such a formulation, we consider regularizations of the convective term that preserve the symmetry and conservation properties exactly. This requirement yielded a novel class of regularizations (Computers & Fluids 37 (2008) 887) that restrain the convective production of smaller and smaller scales of motion in an unconditionally stable manner, meaning that the velocity cannot blow up in the energy-norm (in 2D also: enstrophy-norm). The numerical algorithm used to solve the governing equations must preserve the symmetry and conservation properties too. To do so, one of the most critical issues is the discrete filtering. The method requires a list of properties that, in general, are not preserved by classical filters for LES unless they are imposed a posteriori. In the present paper, we propose a novel class of discrete filters that preserves such properties per se. They are based on polynomial functions of the discrete diffusive operator, ˜D, with the general form F = I + PM m=1 dm ˜D m. Then, the coefficients, dm, follow from the requirement that, at the smallest grid scale kc, the amount by which the interactions between the wavevector-triples (kc, kc − q, q) are damped must become virtually independent of the q-th Fourier-mode. This allows an optimal control of the subtle balance between convection and diffusion at the smallest grid scale to stop the vortex-stretching. Finally, the proposed method is tested for an air-filled differentially heated cavity of height aspect ratio 4.

  • Efficiency of large-scale CFD simulations on modern supercomputers using thousands of CPUS and hybrid MPI+OPENMP parallelization

     Gorobets, Andrey; Borrell Pol, Ricard; Trias Miquel, Francesc Xavier; Kozubskaya, T.K.; Oliva Llena, Asensio
    European Conference on Computational Fluid Dynamics
    p. 1-12
    Presentation's date: 2010-06-17
    Presentation of work at congresses

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    This work represents an experience in using the hybrid parallel model to perform large-scale DNS. Advantages of the hybrid approach compared to the MPI-only approach are presented and discussed. The use of OpenMP in addition to MPI is demonstrated for modelling of compressible and incompressible flows using both structured and unstructured meshes. A parallel Poisson solver for incompressible flows with one periodic direction extended with the hybrid parallelization is presented. A two-level domain decomposition approach is considered for improving parallel algorithms for compressible flows. An alternative strategy with partial data replication is represented as well. Several DNS examples with mesh sizes varying from 106 to 108 control volumes are given to demonstrate e±cient usage of the upgraded algorithms. Performance tests and simulations have been carried out on several parallel systems including Marenostrum, MVS-100000 and Lomonosov supercomputers.

  • Parameter-free modelling of a turbulent differentially heated cavity with Rayleigh number up to 10e11

     Trias Miquel, Francesc Xavier; Soria Guerrero, Manel; Gorobets, Andrey; Verstappen, R.W.C.P.
    International Symposium on Turbulence, Heat and Mass Transfer
    p. 523-526
    Presentation's date: 2009-09-16
    Presentation of work at congresses

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    Since direct numerical simulations of natural convection in a differentially heated cavity cannot be performed at high Rayleigh numbers, a dynamically less complex mathematical formulation is sought. In the quest for such a formulation, we consider regularizations (smooth approximations) of the nonlinearity. The regularization method basically alters the convective terms to reduce the production of small scales of motion by means of vortex stretching. In doing so, we propose to preserve the symmetry and conservation properties of the convective terms exactly. This requirement yielded a novel class of regularizations that restrain the convective production of smaller and smaller scales of motion by means of vortex stretching in an unconditional stable manner, meaning that the velocity cannot blow up in the energy-norm (in 2D also: enstrophy-norm). The numerical algorithm used to solve the governing equations preserves the symmetry and conservation properties too. In the present work we propose to determine the filter length dynamically with the requirement that the vortex stretching must be stopped at the scale set by the grid. Finally, the proposed parameter-free regularization model is successfully tested for a turbulent natural convection flow in an air-filled differentially heated cavity of aspect ratio 4 with Rayleigh number up to 10 11.

  • CENTRE TECNOLOGIC TRANSFERENCIA CALOR

     Sadurni Caballol, Alexandre; Rigola Serrano, Joaquim; Perez Segarra, Carlos David; Trias Miquel, Francesc Xavier; Morales Ruiz, Sergio; Jaramillo Ibarra, Julian Ernesto; Capdevila Paramio, Roser; Rodriguez Pérez, Ivette Maria; Soria Guerrero, Manel; Lopez Mas, Joan; Torras Ortiz, Santiago; Carmona Muñoz, Angel; Oliet Casasayas, Carles; Castro Gonzalez, Jesus; Lehmkuhl Barba, Oriol; Ablanque Mejia, Nicolas; Kizildag, Deniz; Borrell Pol, Ricard; Gorobets, Andrey; Mohan Damle, Rashmin; Oliva Llena, Asensio
    Competitive project

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