Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3193
Thu, 26 May 2022 20:02:06 GMT2022-05-26T20:02:06ZDNS of mass transfer in turbulent bubbly flow in a vertical pipe
http://hdl.handle.net/2117/367458
DNS of mass transfer in turbulent bubbly flow in a vertical pipe
Balcázar Arciniega, Néstor; Rigola Serrano, Joaquim; Oliva Llena, Asensio
The present research focuses on the DNS of mass transfer in gravity-driven turbulent bubbly flow in a vertical pipe, at a high Reynolds number (Re approximates to 1000). The objective is to compute the mass transfer coefficient included in the Sherwood number (Sh), as a function of the Reynolds (Re) number, Damkoler (Da) number for first-order chemical reaction, Schmidt (Sc) number, bubble fraction (BF), and confinement ratio (CR). Indeed, Sh = Sh(Re, Sc, BF, Da, CR), where Re=Re(Eo, Mo, BF, CR), Mo is the Morton number, Eo is the Eotvos number, and physical properties ratios are set to 100. A novel unstructured multiple-marker conservative level-set method for mass transfer in bubbly flows is employed to perform present simulations, in order to circunvent the numerical coalescence of bubbles. Navier-Stokes equations, conservative level-set (CLS) and chemical species transport equations are solved by the finite-volume method on collocated unstructured meshes. Thermodynamic equilibrium relates the concentration of chemical species at the interface by the so-called Henry's law. The pressure-velocity coupling is performed by the fractional-step projection method, whereas surface tension is computed by the continuous surface force model extended to the multiple markers CLS method. Verifications and validations of the numerical methods have been reported in our previous works. Based on our last efforts performed to research mass transfer in gravity-driven bubble swarms on unconfined domains, this research is a further step to include the wall's effect through the confinement ratio (CR). Thus, this work unravels the impact of CR on Sh, at Re = O(1000), whereas the remaining parameters are kept constant.
Tue, 17 May 2022 17:24:06 GMThttp://hdl.handle.net/2117/3674582022-05-17T17:24:06ZBalcázar Arciniega, NéstorRigola Serrano, JoaquimOliva Llena, AsensioThe present research focuses on the DNS of mass transfer in gravity-driven turbulent bubbly flow in a vertical pipe, at a high Reynolds number (Re approximates to 1000). The objective is to compute the mass transfer coefficient included in the Sherwood number (Sh), as a function of the Reynolds (Re) number, Damkoler (Da) number for first-order chemical reaction, Schmidt (Sc) number, bubble fraction (BF), and confinement ratio (CR). Indeed, Sh = Sh(Re, Sc, BF, Da, CR), where Re=Re(Eo, Mo, BF, CR), Mo is the Morton number, Eo is the Eotvos number, and physical properties ratios are set to 100. A novel unstructured multiple-marker conservative level-set method for mass transfer in bubbly flows is employed to perform present simulations, in order to circunvent the numerical coalescence of bubbles. Navier-Stokes equations, conservative level-set (CLS) and chemical species transport equations are solved by the finite-volume method on collocated unstructured meshes. Thermodynamic equilibrium relates the concentration of chemical species at the interface by the so-called Henry's law. The pressure-velocity coupling is performed by the fractional-step projection method, whereas surface tension is computed by the continuous surface force model extended to the multiple markers CLS method. Verifications and validations of the numerical methods have been reported in our previous works. Based on our last efforts performed to research mass transfer in gravity-driven bubble swarms on unconfined domains, this research is a further step to include the wall's effect through the confinement ratio (CR). Thus, this work unravels the impact of CR on Sh, at Re = O(1000), whereas the remaining parameters are kept constant.Transient Thermal Management of Vapor Cycles to Simulate Aircraft Electrical Environment Control Systems
http://hdl.handle.net/2117/367457
Transient Thermal Management of Vapor Cycles to Simulate Aircraft Electrical Environment Control Systems
Ablanque Mejía, Nicolás; Torras Ortiz, Santiago; Oliet Casasayas, Carles; Rigola Serrano, Joaquim; Pérez Segarra, Carlos David
A Modelica library has been developed to simulate both transient and steady state of vapor cycle systems (VCS) integrated within Electrical Environment Control Systems (E-ECS) architectures applied in the thermal management of aircrafts. The numerical resolution of each one of different components: heat exchangers with special attention on two-phase due to their non-linearity; compressors based on parametric curves, valves, accumulators, and auxiliary elements, are detailed, looking for multi-level approach and object-oriented nature. Strategies for transient loop resolution system are also analyzed. A compromise between fast and robust resolution with a enough accuracy has been assured. Numerical results obtained are devoted not only to highlight the system and components robustness with low computational time, but also allow having a better understanding of system behavior on heat exchanger performance, refrigerant mass flow management, initialization cases, system control and transient conditions, becoming a virtual tool for real working conditions.
Tue, 17 May 2022 17:11:02 GMThttp://hdl.handle.net/2117/3674572022-05-17T17:11:02ZAblanque Mejía, NicolásTorras Ortiz, SantiagoOliet Casasayas, CarlesRigola Serrano, JoaquimPérez Segarra, Carlos DavidA Modelica library has been developed to simulate both transient and steady state of vapor cycle systems (VCS) integrated within Electrical Environment Control Systems (E-ECS) architectures applied in the thermal management of aircrafts. The numerical resolution of each one of different components: heat exchangers with special attention on two-phase due to their non-linearity; compressors based on parametric curves, valves, accumulators, and auxiliary elements, are detailed, looking for multi-level approach and object-oriented nature. Strategies for transient loop resolution system are also analyzed. A compromise between fast and robust resolution with a enough accuracy has been assured. Numerical results obtained are devoted not only to highlight the system and components robustness with low computational time, but also allow having a better understanding of system behavior on heat exchanger performance, refrigerant mass flow management, initialization cases, system control and transient conditions, becoming a virtual tool for real working conditions.Advanced techniques for grau area mitigation in DES simulations and their effectes on the subsonic round jet acoustic spectra
http://hdl.handle.net/2117/367010
Advanced techniques for grau area mitigation in DES simulations and their effectes on the subsonic round jet acoustic spectra
Duben, Alexey; Ruano Pérez, Jesús; Trias Miquel, Francesc Xavier; Rigola Serrano, Joaquim
The research dedicated to the investigation of different gray-area mitigation approaches towards accurate aerodynamics and aeroacoustics is presented. The recent modifications of hybrid RANS-LES DDES approach based on combinations of new adapting subgrid length scales (~ !, SLA and lsq) and LES models ( and S3QR) are considered. The object of investigation is an immersed subsonic turbulent jet. The simulations are carried out on a set of refining meshes using two different scale-resolving numerical algorithms realized in the compressible codes NOISEtte and OpenFOAM. The evaluation of different approaches is focused on the analysis of far field noise. The results show that all the considered techniques provide appropriate accuracy to predict the noise generated by the turbulent jet. The study clearly demonstrated the importance of both numerical scheme and subgrid turbulence model. The peculiarities of considered approaches are revealed and discussed.
Fri, 06 May 2022 12:38:05 GMThttp://hdl.handle.net/2117/3670102022-05-06T12:38:05ZDuben, AlexeyRuano Pérez, JesúsTrias Miquel, Francesc XavierRigola Serrano, JoaquimThe research dedicated to the investigation of different gray-area mitigation approaches towards accurate aerodynamics and aeroacoustics is presented. The recent modifications of hybrid RANS-LES DDES approach based on combinations of new adapting subgrid length scales (~ !, SLA and lsq) and LES models ( and S3QR) are considered. The object of investigation is an immersed subsonic turbulent jet. The simulations are carried out on a set of refining meshes using two different scale-resolving numerical algorithms realized in the compressible codes NOISEtte and OpenFOAM. The evaluation of different approaches is focused on the analysis of far field noise. The results show that all the considered techniques provide appropriate accuracy to predict the noise generated by the turbulent jet. The study clearly demonstrated the importance of both numerical scheme and subgrid turbulence model. The peculiarities of considered approaches are revealed and discussed.NUMA-Aware Strategies for the Heterogeneous Execution of SPMV on Modern Supercomputers
http://hdl.handle.net/2117/366919
NUMA-Aware Strategies for the Heterogeneous Execution of SPMV on Modern Supercomputers
Álvarez Farré, Xavier; Gorobets, Andrei; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
The sparse matrix-vector product is a widespread operation amongst the scientific computing community. It represents the dominant computational cost in many large-scale simulations relying on iterative methods, and its performance is sensitive to the sparse pattern, the storage format, and kernel implementation, and the target computing architecture. In this work, we are devoted to the efficient execution of the sparse matrix-vector product on (potentially hybrid) modern supercomputers with non-uniform memory access configurations. A hierarchical parallel implementation is proposed to minimize the number of processes participating in distributed-memory parallelization. As a result, a single process per computing node is enough to engage all its hardware and ensure efficient memory access on manycore platforms. The benefits of this approach have been demonstrated on up to 9,600 cores of MareNostrum 4 supercomputer, at Barcelona Supercomputing Center.
Fri, 06 May 2022 07:52:13 GMThttp://hdl.handle.net/2117/3669192022-05-06T07:52:13ZÁlvarez Farré, XavierGorobets, AndreiTrias Miquel, Francesc XavierOliva Llena, AsensioThe sparse matrix-vector product is a widespread operation amongst the scientific computing community. It represents the dominant computational cost in many large-scale simulations relying on iterative methods, and its performance is sensitive to the sparse pattern, the storage format, and kernel implementation, and the target computing architecture. In this work, we are devoted to the efficient execution of the sparse matrix-vector product on (potentially hybrid) modern supercomputers with non-uniform memory access configurations. A hierarchical parallel implementation is proposed to minimize the number of processes participating in distributed-memory parallelization. As a result, a single process per computing node is enough to engage all its hardware and ensure efficient memory access on manycore platforms. The benefits of this approach have been demonstrated on up to 9,600 cores of MareNostrum 4 supercomputer, at Barcelona Supercomputing Center.A General Method to Compute Numerical Dispersion Error
http://hdl.handle.net/2117/366918
A General Method to Compute Numerical Dispersion Error
Ruano Pérez, Jesús; Baez Vidal, Aleix; Rigola Serrano, Joaquim; Trias Miquel, Francesc Xavier
This article presents a new methodology to compute numerical dispersion error. The analysis here presented is not restricted to uniform structured meshes nor linear discrete operators as it does not rely on sinusoids to compute the associated error. When using uniform meshes, the results obtained with the present method collapse onto the obtained with the classic one via an easy change of basis. If non-uniform meshes are used, a new kind of results are obtained which shed some light onto the role stretching has on dispersion error.
Fri, 06 May 2022 07:27:41 GMThttp://hdl.handle.net/2117/3669182022-05-06T07:27:41ZRuano Pérez, JesúsBaez Vidal, AleixRigola Serrano, JoaquimTrias Miquel, Francesc XavierThis article presents a new methodology to compute numerical dispersion error. The analysis here presented is not restricted to uniform structured meshes nor linear discrete operators as it does not rely on sinusoids to compute the associated error. When using uniform meshes, the results obtained with the present method collapse onto the obtained with the classic one via an easy change of basis. If non-uniform meshes are used, a new kind of results are obtained which shed some light onto the role stretching has on dispersion error.On the Interpolation Problem for the Poisson Equation on Collocated Meshes
http://hdl.handle.net/2117/366809
On the Interpolation Problem for the Poisson Equation on Collocated Meshes
Santos Serrano, Daniel; Muela Castro, Jordi; Valle Marchante, Nicolás; Trias Miquel, Francesc Xavier
The appearence of unphysical velocities in highly distorted meshes is a common problem in many simulations. In collocated meshes, this problem arises from the interpolation of the pressure gradient from faces to cells. Using an algebraic form for the classical incompressible Navier-Stokes equations, this problem is adressed. Starting from the work of F. X. Trias et. al. [FX.Trias et al. JCP 258: 246-267, 2014], a new approach for studying the Poisson equation obtained using the Fractional Step Method is found, such as a new interpolator is proposed in order to found a stable solution, which avoid the appearence of these unpleasant velocities. The stability provided by the interpolator is formally proved for cartesian meshes and its rotations, using fully-explicit time discretizations. The construction of the Poisson equation is supported on mimicking the symmetry properties of the differential operators and the Fractional Step Method. Then it is reinterpreted using a recursive application of the Fractional Step Method in order to study the system as an stationary iterative solver. Furthermore, a numerical analysis for unstructured mesh is also provided.
Wed, 04 May 2022 12:52:14 GMThttp://hdl.handle.net/2117/3668092022-05-04T12:52:14ZSantos Serrano, DanielMuela Castro, JordiValle Marchante, NicolásTrias Miquel, Francesc XavierThe appearence of unphysical velocities in highly distorted meshes is a common problem in many simulations. In collocated meshes, this problem arises from the interpolation of the pressure gradient from faces to cells. Using an algebraic form for the classical incompressible Navier-Stokes equations, this problem is adressed. Starting from the work of F. X. Trias et. al. [FX.Trias et al. JCP 258: 246-267, 2014], a new approach for studying the Poisson equation obtained using the Fractional Step Method is found, such as a new interpolator is proposed in order to found a stable solution, which avoid the appearence of these unpleasant velocities. The stability provided by the interpolator is formally proved for cartesian meshes and its rotations, using fully-explicit time discretizations. The construction of the Poisson equation is supported on mimicking the symmetry properties of the differential operators and the Fractional Step Method. Then it is reinterpreted using a recursive application of the Fractional Step Method in order to study the system as an stationary iterative solver. Furthermore, a numerical analysis for unstructured mesh is also provided.NUMA-Aware strategies for the efficient execution of CFD simulations on CPU supercomputers
http://hdl.handle.net/2117/366753
NUMA-Aware strategies for the efficient execution of CFD simulations on CPU supercomputers
Álvarez Farré, Xavier; Gorobets, Andrei; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
The growing variety of computing architectures and the hybridization of high-performance computing systems encourage the research for portable implementations of numerical methods in simulation codes. However, the pursuit of efficient and portable implementations is a rather complex problem. The present work is devoted to the development of portable parallel algorithms, primarily for scale-resolving, time-accurate simulations of incompressible flows with turbulent heat and mass transfer. The heterogeneous computing capability allows for engaging both processors and accelerators efficiently. In addition to computing on accelerators, special attention is paid at efficiency on multiprocessor nodes with significant non-uniform memory access factor. In this work, we study in detail the parallel efficiency and performance for different execution modes on up to ten thousand cores of MareNostrum 4 supercomputer.
Tue, 03 May 2022 18:18:50 GMThttp://hdl.handle.net/2117/3667532022-05-03T18:18:50ZÁlvarez Farré, XavierGorobets, AndreiTrias Miquel, Francesc XavierOliva Llena, AsensioThe growing variety of computing architectures and the hybridization of high-performance computing systems encourage the research for portable implementations of numerical methods in simulation codes. However, the pursuit of efficient and portable implementations is a rather complex problem. The present work is devoted to the development of portable parallel algorithms, primarily for scale-resolving, time-accurate simulations of incompressible flows with turbulent heat and mass transfer. The heterogeneous computing capability allows for engaging both processors and accelerators efficiently. In addition to computing on accelerators, special attention is paid at efficiency on multiprocessor nodes with significant non-uniform memory access factor. In this work, we study in detail the parallel efficiency and performance for different execution modes on up to ten thousand cores of MareNostrum 4 supercomputer.Three-dimensional direct numerical simulation (dns) Of taylor bubbles rising in non-Newtonian environments
http://hdl.handle.net/2117/362608
Three-dimensional direct numerical simulation (dns) Of taylor bubbles rising in non-Newtonian environments
Amani, Ahmad; Castro González, Jesús; Oliva Llena, Asensio
Three-dimensional numerical simulation of Taylor gas bubbles as primary unites of slug flow patterns rising in non-Newtonian environments is performed in the context of Direct Numerical Simulation (DNS) of the governing equations, where the whole physics of fluid motions will be taken into account. State-of-the-art numerical tools are proposed to tackle the numerical challenges in the DNS study of this problem. E.g. a coupled level-set volume-of-fluid (CLSVOF) interface capturing method is used to solve the topological changes of the interface. Physical formulations are integrated with moving-mesh (MM) technique to decrease the computational cost of 3D simulations and adaptivemesh-refinement (AMR) technique to increase the local accuracy around the interface. The governing equations are solved using High-Performance Computing (HPC) parallel approaches. To the best of the
authors’ knowledge, this is the first work dealing with three-dimensional direct numerical simulation of Taylor bubbles rising in non-Newtonian environments.
Fri, 18 Feb 2022 07:32:28 GMThttp://hdl.handle.net/2117/3626082022-02-18T07:32:28ZAmani, AhmadCastro González, JesúsOliva Llena, AsensioThree-dimensional numerical simulation of Taylor gas bubbles as primary unites of slug flow patterns rising in non-Newtonian environments is performed in the context of Direct Numerical Simulation (DNS) of the governing equations, where the whole physics of fluid motions will be taken into account. State-of-the-art numerical tools are proposed to tackle the numerical challenges in the DNS study of this problem. E.g. a coupled level-set volume-of-fluid (CLSVOF) interface capturing method is used to solve the topological changes of the interface. Physical formulations are integrated with moving-mesh (MM) technique to decrease the computational cost of 3D simulations and adaptivemesh-refinement (AMR) technique to increase the local accuracy around the interface. The governing equations are solved using High-Performance Computing (HPC) parallel approaches. To the best of the
authors’ knowledge, this is the first work dealing with three-dimensional direct numerical simulation of Taylor bubbles rising in non-Newtonian environments.Unstructured Level-Set Method For Saturated Liquid-Vapor Phase Change
http://hdl.handle.net/2117/362446
Unstructured Level-Set Method For Saturated Liquid-Vapor Phase Change
Balcázar Arciniega, Néstor; Rigola Serrano, Joaquim; Oliva Llena, Asensio
A novel conservative level-set method for saturated liquid-vapor phase change on unstruc-tured meshes is introduced. Transport equations are discretized by the finite-volume method on col-located unstructured grids. Mass transfer promoted by thermal phase change is computed using theenergy jump condition at the interface, as a function of the temperature gradient. The fractional-stepprojection method is used for solving the pressure-velocity coupling, convective terms are discretized byunstructured flux-limiter schemes, central difference scheme is used for discretization of diffusive terms.Verification and validation cases have been undertaken to prove the accuracy and robustness of the nu-merical methods, including simulation of the Stefan problem, and film boiling on a cylindrical surface.Excellent agreement between numerical solutions against analytical solution and empirical correlationsfrom the literature is reported.
Tue, 15 Feb 2022 17:47:05 GMThttp://hdl.handle.net/2117/3624462022-02-15T17:47:05ZBalcázar Arciniega, NéstorRigola Serrano, JoaquimOliva Llena, AsensioA novel conservative level-set method for saturated liquid-vapor phase change on unstruc-tured meshes is introduced. Transport equations are discretized by the finite-volume method on col-located unstructured grids. Mass transfer promoted by thermal phase change is computed using theenergy jump condition at the interface, as a function of the temperature gradient. The fractional-stepprojection method is used for solving the pressure-velocity coupling, convective terms are discretized byunstructured flux-limiter schemes, central difference scheme is used for discretization of diffusive terms.Verification and validation cases have been undertaken to prove the accuracy and robustness of the nu-merical methods, including simulation of the Stefan problem, and film boiling on a cylindrical surface.Excellent agreement between numerical solutions against analytical solution and empirical correlationsfrom the literature is reported.A highly portable heterogeneous implementation of a Poisson solver for flows with one periodic direction
http://hdl.handle.net/2117/362140
A highly portable heterogeneous implementation of a Poisson solver for flows with one periodic direction
Alsalti Baldellou, Àdel; Trias Miquel, Francesc Xavier; Álvarez Farré, Xavier; Oliva Llena, Asensio
The portability of codes has become a major advantage given the continuous development of new architectures for numerical applications, as well as the progressive incorporation of accelerators in modern supercomputers. Following this trend, we have adopted an algebraic approach in the implementation of a Poisson solver for incompressible flows with one periodic direction. This approach, which basically consists of adapting a reduced set of fundamental operations to any architecture (such as the sparse matrixvector product or the dot product of two vectors), allows us to efficiently port our applications to any heterogeneous supercomputers in an easy manner. More particularly, our three-dimensional solver takes advantage of the existing periodic dimension (by means of a Fourier decomposition) to later execute overlapped data transpositions among devices, which conveniently share the workload with their CPU hosts, and solve the resulting two-dimensional decoupled subsystems.
Fri, 11 Feb 2022 09:29:16 GMThttp://hdl.handle.net/2117/3621402022-02-11T09:29:16ZAlsalti Baldellou, ÀdelTrias Miquel, Francesc XavierÁlvarez Farré, XavierOliva Llena, AsensioThe portability of codes has become a major advantage given the continuous development of new architectures for numerical applications, as well as the progressive incorporation of accelerators in modern supercomputers. Following this trend, we have adopted an algebraic approach in the implementation of a Poisson solver for incompressible flows with one periodic direction. This approach, which basically consists of adapting a reduced set of fundamental operations to any architecture (such as the sparse matrixvector product or the dot product of two vectors), allows us to efficiently port our applications to any heterogeneous supercomputers in an easy manner. More particularly, our three-dimensional solver takes advantage of the existing periodic dimension (by means of a Fourier decomposition) to later execute overlapped data transpositions among devices, which conveniently share the workload with their CPU hosts, and solve the resulting two-dimensional decoupled subsystems.