CTTC - Centre Tecnològic de la Transferència de Calorhttp://hdl.handle.net/2117/31902022-05-19T10:06:52Z2022-05-19T10:06:52ZDNS of mass transfer in turbulent bubbly flow in a vertical pipeBalcázar Arciniega, NéstorRigola Serrano, JoaquimOliva Llena, Asensiohttp://hdl.handle.net/2117/3674582022-05-17T17:30:45Z2022-05-17T17:24:06ZDNS 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.
2022-05-17T17:24:06ZBalcázar 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 SystemsAblanque Mejía, NicolásTorras Ortiz, SantiagoOliet Casasayas, CarlesRigola Serrano, JoaquimPérez Segarra, Carlos Davidhttp://hdl.handle.net/2117/3674572022-05-17T17:20:25Z2022-05-17T17:11:02ZTransient 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.
2022-05-17T17:11:02ZAblanque 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 spectraDuben, AlexeyRuano Pérez, JesúsTrias Miquel, Francesc XavierRigola Serrano, Joaquimhttp://hdl.handle.net/2117/3670102022-05-17T12:52:40Z2022-05-06T12:38:05ZAdvanced 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.
2022-05-06T12:38:05ZDuben, 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 SupercomputersÁlvarez Farré, XavierGorobets, AndreiTrias Miquel, Francesc XavierOliva Llena, Asensiohttp://hdl.handle.net/2117/3669192022-05-17T11:32:58Z2022-05-06T07:52:13ZNUMA-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.
2022-05-06T07:52:13ZÁlvarez 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 ErrorRuano Pérez, JesúsBaez Vidal, AleixRigola Serrano, JoaquimTrias Miquel, Francesc Xavierhttp://hdl.handle.net/2117/3669182022-05-17T10:38:34Z2022-05-06T07:27:41ZA 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.
2022-05-06T07:27:41ZRuano 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 implementation of flux limiters in algebraic frameworksValle Marchante, NicolásÁlvarez Farré, XavierGorobets, AndreiCastro González, JesúsOliva Llena, AsensioTrias Miquel, Francesc Xavierhttp://hdl.handle.net/2117/3669172022-05-17T10:14:27Z2022-05-06T06:54:44ZOn the implementation of flux limiters in algebraic frameworks
Valle Marchante, Nicolás; Álvarez Farré, Xavier; Gorobets, Andrei; Castro González, Jesús; Oliva Llena, Asensio; Trias Miquel, Francesc Xavier
The use of flux limiters is widespread within the scientific computing community to capture shock dis- continuities and are of paramount importance for the temporal integration of high-speed aerodynamics, multiphase flows and hyperbolic equations in general. Meanwhile, the breakthrough of new computing architectures and the hybridization of supercomputer systems pose a huge portability challenge, particularly for legacy codes, since the computing subroutines that form the algorithms, the so-called kernels, must be adapted to various complex parallel program- ming paradigms. From this perspective, the development of innovative implementations relying on a minimalist set of kernels simplifies the deployment of scientific computing software on state-of-the-art supercomputers, while it requires the reformulation of algorithms, such as the aforementioned flux lim- iters. Equipped with basic algebraic topology and graph theory underlying the classical mesh concept, a new flux limiter formulation is presented based on the adoption of algebraic data structures and kernels. As a result, traditional flux limiters are cast into a stream of only two types of computing kernels: sparse matrix-vector multiplication and generalized pointwise binary operators. The newly proposed formulation eases the deployment of such a numerical technique in massively parallel, potentially hybrid, computing systems and is demonstrated for a canonical advection problem.
2022-05-06T06:54:44ZValle Marchante, NicolásÁlvarez Farré, XavierGorobets, AndreiCastro González, JesúsOliva Llena, AsensioTrias Miquel, Francesc XavierThe use of flux limiters is widespread within the scientific computing community to capture shock dis- continuities and are of paramount importance for the temporal integration of high-speed aerodynamics, multiphase flows and hyperbolic equations in general. Meanwhile, the breakthrough of new computing architectures and the hybridization of supercomputer systems pose a huge portability challenge, particularly for legacy codes, since the computing subroutines that form the algorithms, the so-called kernels, must be adapted to various complex parallel program- ming paradigms. From this perspective, the development of innovative implementations relying on a minimalist set of kernels simplifies the deployment of scientific computing software on state-of-the-art supercomputers, while it requires the reformulation of algorithms, such as the aforementioned flux lim- iters. Equipped with basic algebraic topology and graph theory underlying the classical mesh concept, a new flux limiter formulation is presented based on the adoption of algebraic data structures and kernels. As a result, traditional flux limiters are cast into a stream of only two types of computing kernels: sparse matrix-vector multiplication and generalized pointwise binary operators. The newly proposed formulation eases the deployment of such a numerical technique in massively parallel, potentially hybrid, computing systems and is demonstrated for a canonical advection problem.A new general method to compute dispersion errors on Cartesian stretched meshes for both linear and non-linear operatorsRuano Pérez, JesúsBaez Vidal, AleixRigola Serrano, JoaquimTrias Miquel, Francesc Xavierhttp://hdl.handle.net/2117/3668242022-05-17T10:44:29Z2022-05-04T15:07:54ZA new general method to compute dispersion errors on Cartesian stretched meshes for both linear and non-linear operators
Ruano Pérez, Jesús; Baez Vidal, Aleix; Rigola Serrano, Joaquim; Trias Miquel, Francesc Xavier
The present article presents a new analysis for the dispersion error and the methodology to evaluate it numerically. Here we present the spectral properties of several convective schemes, including non-linear ones, on Cartesian stretched grids for linear advection problems. Results obtained with this method when applied to uniform structured meshes, converge to the results obtained with the classical method for all the studied schemes. Additionally, effects on the time step depending on which scheme is used are considered using the proposed method. The extracted conclusions taken into account both errors and computational cost allow to propose an optimal scheme according to the selected meshing strategy.
2022-05-04T15:07:54ZRuano Pérez, JesúsBaez Vidal, AleixRigola Serrano, JoaquimTrias Miquel, Francesc XavierThe present article presents a new analysis for the dispersion error and the methodology to evaluate it numerically. Here we present the spectral properties of several convective schemes, including non-linear ones, on Cartesian stretched grids for linear advection problems. Results obtained with this method when applied to uniform structured meshes, converge to the results obtained with the classical method for all the studied schemes. Additionally, effects on the time step depending on which scheme is used are considered using the proposed method. The extracted conclusions taken into account both errors and computational cost allow to propose an optimal scheme according to the selected meshing strategy.On the Interpolation Problem for the Poisson Equation on Collocated MeshesSantos Serrano, DanielMuela Castro, JordiValle Marchante, NicolásTrias Miquel, Francesc Xavierhttp://hdl.handle.net/2117/3668092022-05-17T12:42:56Z2022-05-04T12:52:14ZOn 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.
2022-05-04T12:52:14ZSantos 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 supercomputersÁlvarez Farré, XavierGorobets, AndreiTrias Miquel, Francesc XavierOliva Llena, Asensiohttp://hdl.handle.net/2117/3667532022-05-17T10:14:00Z2022-05-03T18:18:50ZNUMA-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.
2022-05-03T18:18:50ZÁlvarez 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.Energy and exergy analysis of an absorption system with working pairs LiBr-H2O and Carrol-H2O at applications of cooling and heatingZheng, JianCastro González, JesúsOliva Llena, AsensioOliet Casasayas, Carleshttp://hdl.handle.net/2117/3666022022-05-03T09:12:28Z2022-04-29T12:47:02ZEnergy and exergy analysis of an absorption system with working pairs LiBr-H2O and Carrol-H2O at applications of cooling and heating
Zheng, Jian; Castro González, Jesús; Oliva Llena, Asensio; Oliet Casasayas, Carles
In this work, an air-cooled, single effect solar-driven absorption system is being evaluated from the point of view of 1 and 2 thermodynamic principles for two different applications: absorption chiller and heat pump. One of the most widely used working pairs, LiBr-HO, is applied in this study due to its high performance in the absorption cycle. Their performance is compared with another working pair Carrol-HO (Carrol contains LiBr and EG -Ethylene glycol- with a mass ratio of 4.5:1). The Carrol solution has the advantage of reducing the crystallization risk at the high concentration solution that enters the absorber. The numerical modelling was implemented on a modular object-oriented simulation platform (NEST platform tool), which allows linking different components, considered objects. In the simulations performed, the heat source temperature in the system is in the range of 70–90 C, and the inlet temperature at evaporator secondary circuit at chiller application is fixed in two values, 9C and 14C, and for heat pump application in 0C and -5C. Moreover, EG is added to the evaporator at heat pump application to prevent the refrigerant water from freezing below zero. The studied mass concentration range of EG of 10–40%. The result shows the of an absorption chiller and heat pump are around 0.7 and 1.6, respectively, and the values are 0.2-0.6 at chiller application and 0.5-1.5 at heat pump application. When compared with LiBr system, Carrol system has about 6.4% higher , about 6.3% higher , and a decrease of about 19% of cooling capacity. In the heat pump application, the heat source temperature should be lower than 90C, and EG concentration at evaporator has been chosen as 30% as an optimal value. According to the operation condition, this EG concentration has been determined to avoid freezing in the evaporator in the studied working range. However, too much EG significantly decreases the pressure in the evaporator and increases the viscosity, hence will increase the maintenance of equipment as more vacuum tightness is required.
2022-04-29T12:47:02ZZheng, JianCastro González, JesúsOliva Llena, AsensioOliet Casasayas, CarlesIn this work, an air-cooled, single effect solar-driven absorption system is being evaluated from the point of view of 1 and 2 thermodynamic principles for two different applications: absorption chiller and heat pump. One of the most widely used working pairs, LiBr-HO, is applied in this study due to its high performance in the absorption cycle. Their performance is compared with another working pair Carrol-HO (Carrol contains LiBr and EG -Ethylene glycol- with a mass ratio of 4.5:1). The Carrol solution has the advantage of reducing the crystallization risk at the high concentration solution that enters the absorber. The numerical modelling was implemented on a modular object-oriented simulation platform (NEST platform tool), which allows linking different components, considered objects. In the simulations performed, the heat source temperature in the system is in the range of 70–90 C, and the inlet temperature at evaporator secondary circuit at chiller application is fixed in two values, 9C and 14C, and for heat pump application in 0C and -5C. Moreover, EG is added to the evaporator at heat pump application to prevent the refrigerant water from freezing below zero. The studied mass concentration range of EG of 10–40%. The result shows the of an absorption chiller and heat pump are around 0.7 and 1.6, respectively, and the values are 0.2-0.6 at chiller application and 0.5-1.5 at heat pump application. When compared with LiBr system, Carrol system has about 6.4% higher , about 6.3% higher , and a decrease of about 19% of cooling capacity. In the heat pump application, the heat source temperature should be lower than 90C, and EG concentration at evaporator has been chosen as 30% as an optimal value. According to the operation condition, this EG concentration has been determined to avoid freezing in the evaporator in the studied working range. However, too much EG significantly decreases the pressure in the evaporator and increases the viscosity, hence will increase the maintenance of equipment as more vacuum tightness is required.