Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3193
2017-06-26T15:54:23ZA finite-volume/level-set interface capturing method for unstructured grids: Simulations of bubbles rising through viscous liquids
http://hdl.handle.net/2117/105758
A finite-volume/level-set interface capturing method for unstructured grids: Simulations of bubbles rising through viscous liquids
Balcázar Arciniega, Néstor; Jofre Cruanyes, Lluís; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Castro González, Jesús; Oliva Llena, Asensio
A numerical method is developed for simulating two-phase flows with moving inter-phase boundaries, which is integrated in a finite-volume framework on collocated unstructured grids of arbitrary element type. The location, geometry and the movement of the discontinuities are described by the conservative levelset method. The proposed algorithm is validated with experimental results of the buoyant rise of an isolated bubble. Then the method is applied to simulate the interaction between two bubbles during their buoyant rise. Finally, simulations for a set of bubbles with the same diameter initially placed in a random pattern in a periodic cylindrical duct are also carried out. In general, a good agreement is found between the current simulations and results reported in the literature.
2017-06-23T09:33:15ZBalcázar Arciniega, NéstorJofre Cruanyes, LluísLehmkuhl Barba, OriolRigola Serrano, JoaquimCastro González, JesúsOliva Llena, AsensioA numerical method is developed for simulating two-phase flows with moving inter-phase boundaries, which is integrated in a finite-volume framework on collocated unstructured grids of arbitrary element type. The location, geometry and the movement of the discontinuities are described by the conservative levelset method. The proposed algorithm is validated with experimental results of the buoyant rise of an isolated bubble. Then the method is applied to simulate the interaction between two bubbles during their buoyant rise. Finally, simulations for a set of bubbles with the same diameter initially placed in a random pattern in a periodic cylindrical duct are also carried out. In general, a good agreement is found between the current simulations and results reported in the literature.Conservative discretization of multiphase flow with high density ratios
http://hdl.handle.net/2117/105755
Conservative discretization of multiphase flow with high density ratios
Jofre Cruanyes, Lluís; Lehmkuhl Barba, Oriol; Balcázar Arciniega, Néstor; Castro González, Jesús; Rigola Serrano, Joaquim; Oliva Llena, Asensio
The computation of multiphase flows presenting high density ratios, where the fluids involved are considered immiscible, are of great importance for fundamental physics and industrial applications; such as the study of liquid-gas interfaces, wave motion, simulation of bubbly flows and atomization, injection in diesel engines, chemical processes and others. This work presents and analyzes a collocated and staggered finite-volume mesh discretizations suitable for three-dimensional unstructured meshes, which are able to simulate immiscible multiphase flows with high density ratios. More over, these mesh schemes numerically conserve mass and momentum while minimize errors in the conservation of kinetic energy.
2017-06-23T09:31:59ZJofre Cruanyes, LluísLehmkuhl Barba, OriolBalcázar Arciniega, NéstorCastro González, JesúsRigola Serrano, JoaquimOliva Llena, AsensioThe computation of multiphase flows presenting high density ratios, where the fluids involved are considered immiscible, are of great importance for fundamental physics and industrial applications; such as the study of liquid-gas interfaces, wave motion, simulation of bubbly flows and atomization, injection in diesel engines, chemical processes and others. This work presents and analyzes a collocated and staggered finite-volume mesh discretizations suitable for three-dimensional unstructured meshes, which are able to simulate immiscible multiphase flows with high density ratios. More over, these mesh schemes numerically conserve mass and momentum while minimize errors in the conservation of kinetic energy.Large eddy simulation model assessment of the turbulent flow through dynamic compressor valves
http://hdl.handle.net/2117/105134
Large eddy simulation model assessment of the turbulent flow through dynamic compressor valves
Estruch Pérez, Olga; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio; Pérez Segarra, Carlos David
The present paper attempts the dynamic simulation of the fluid flow through the valve reed taking into account valve movement due to piston displacement. This work widens previous studies based on numerical experiments with static geometry and constant boundary conditions. Hence, in this work attends the newly in-house implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a three-dimensional explicit finite volume fractional-step algorithm formulated in a second-order, conservative and collocated unstructured grid arrangement.
Large eddy simulation is performed to solve the turbulent flow, using the subgrid scale WALE model. A radial basis function interpolation procedure is used to dynamically move the mesh according with the displacement of the valve. A simplified geometry of an axial hole plus a radial diffuser with a piston based inlet condition is considered. The valve dynamics is assumed to be given by a law according modal analysis of valve reed.
2017-06-05T15:51:50ZEstruch Pérez, OlgaLehmkuhl Barba, OriolRigola Serrano, JoaquimOliva Llena, AsensioPérez Segarra, Carlos DavidThe present paper attempts the dynamic simulation of the fluid flow through the valve reed taking into account valve movement due to piston displacement. This work widens previous studies based on numerical experiments with static geometry and constant boundary conditions. Hence, in this work attends the newly in-house implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a three-dimensional explicit finite volume fractional-step algorithm formulated in a second-order, conservative and collocated unstructured grid arrangement.
Large eddy simulation is performed to solve the turbulent flow, using the subgrid scale WALE model. A radial basis function interpolation procedure is used to dynamically move the mesh according with the displacement of the valve. A simplified geometry of an axial hole plus a radial diffuser with a piston based inlet condition is considered. The valve dynamics is assumed to be given by a law according modal analysis of valve reed.Hot run test results of a validation optimized water-ice phase change heat accumulator and comparison to numerical analysis¿X¿¿c
http://hdl.handle.net/2117/105102
Hot run test results of a validation optimized water-ice phase change heat accumulator and comparison to numerical analysis¿X¿¿c
Riccius, Jorg; Leiner, Johannes; Castro González, Jesús; Rigola Serrano, Joaquim
Phase change heat accumulators are essential devices for the thermal management of multiple ignition, electric pump driven in-space propulsion systems such as the Low Cost Cryogenic Propulsion (LCCP) system [1], [2]. For Low Temperature Accumulators (LTAs), water/ice is of special interest as phase change material because of its high heat capacity and high latent heat. Therefore, an analysis of the phase change behaviour of both, this heat storage material and an heat transfer medium were performed in the framework of the ISP1 project [2], [3]. In the experiments shown in the current paper, gaseous nitrogen at 80°C
is injected to the inlet of the heat transfer tube. By passing through the heat transfer tube, it causes the heat storage medium ice to melt and the hot nitrogen is cooled down.
The phase change behaviour of the phase change material ice and the heat transfer process from nitrogen to the ice were analysed experimentally in a qualitative and a quantitative way. Finally, the obtained experimental results are compared to the analysis results of theoretical phase-change models carried out by the ISP-1 partner institution UPC [7], [8], [9].
2017-06-01T15:05:50ZRiccius, JorgLeiner, JohannesCastro González, JesúsRigola Serrano, JoaquimPhase change heat accumulators are essential devices for the thermal management of multiple ignition, electric pump driven in-space propulsion systems such as the Low Cost Cryogenic Propulsion (LCCP) system [1], [2]. For Low Temperature Accumulators (LTAs), water/ice is of special interest as phase change material because of its high heat capacity and high latent heat. Therefore, an analysis of the phase change behaviour of both, this heat storage material and an heat transfer medium were performed in the framework of the ISP1 project [2], [3]. In the experiments shown in the current paper, gaseous nitrogen at 80°C
is injected to the inlet of the heat transfer tube. By passing through the heat transfer tube, it causes the heat storage medium ice to melt and the hot nitrogen is cooled down.
The phase change behaviour of the phase change material ice and the heat transfer process from nitrogen to the ice were analysed experimentally in a qualitative and a quantitative way. Finally, the obtained experimental results are compared to the analysis results of theoretical phase-change models carried out by the ISP-1 partner institution UPC [7], [8], [9].Modelling and experimental validation of the heat accumulator in a Low Trust Cryogenic Propulsion (LTCP) system¿¿e,
http://hdl.handle.net/2117/105100
Modelling and experimental validation of the heat accumulator in a Low Trust Cryogenic Propulsion (LTCP) system¿¿e,
Torras Ortiz, Santiago; Castro González, Jesús; Rigola Serrano, Joaquim; Morales, Sergio; Riccius, Jorg; Leiner, Johannes
The study of one of the components, the heat accumulator, of Low Thrust Cryogenic Propulsion systems (LTCP), is of scientific interest in the framework of ISP-1 project [1]. This device stores thermal energy from the fuel cell that provides electrical energy to the whole system. This thermal energy is employed for the pressurization of the propellant tanks. A numerical model is being developed [2] in order to predict the thermal behaviour of the heat accumulator and having a tool for its design in the next future. The numerical model is validated with experimental results of ISP-1 partners (DLR) [3], [4].
2017-06-01T12:43:04ZTorras Ortiz, SantiagoCastro González, JesúsRigola Serrano, JoaquimMorales, SergioRiccius, JorgLeiner, JohannesThe study of one of the components, the heat accumulator, of Low Thrust Cryogenic Propulsion systems (LTCP), is of scientific interest in the framework of ISP-1 project [1]. This device stores thermal energy from the fuel cell that provides electrical energy to the whole system. This thermal energy is employed for the pressurization of the propellant tanks. A numerical model is being developed [2] in order to predict the thermal behaviour of the heat accumulator and having a tool for its design in the next future. The numerical model is validated with experimental results of ISP-1 partners (DLR) [3], [4].Experimental and numerical investigation of H2O vapor absorption processes in falling film of LiBr aqueous solution in vertical tubes
http://hdl.handle.net/2117/105085
Experimental and numerical investigation of H2O vapor absorption processes in falling film of LiBr aqueous solution in vertical tubes
Castro González, Jesús; Farnós Baulenas, Joan; García Rivera, Eduardo; Oliva Llena, Asensio
The LiBr-H2O absorption systems are used mainly in large cooling capacity applications (industry, large buildings, etc.), therefore require water from cooling towers to reject heat. However, if middle and low capacity are required (commercial and residential systems), absorption machines should be air-cooled in order to become competitive [1-4].
The absorber represents a major critical component in absorption systems and one of the key issues, in it is the combined heat and mass transfer in the absorption process. For this reason the development of mathematical models for the simulation and experimental data for the validation are always useful tools for the design and improvement of falling film vertical absorbers. A testing device has been designed and built for reproducing absorption phenomena in vertical tubes with the primary objective to obtain experimental data in LiBr-H2O vertical absorbers. The versatility of the experiment allows to obtain a wide range of data.
2017-05-31T17:30:56ZCastro González, JesúsFarnós Baulenas, JoanGarcía Rivera, EduardoOliva Llena, AsensioThe LiBr-H2O absorption systems are used mainly in large cooling capacity applications (industry, large buildings, etc.), therefore require water from cooling towers to reject heat. However, if middle and low capacity are required (commercial and residential systems), absorption machines should be air-cooled in order to become competitive [1-4].
The absorber represents a major critical component in absorption systems and one of the key issues, in it is the combined heat and mass transfer in the absorption process. For this reason the development of mathematical models for the simulation and experimental data for the validation are always useful tools for the design and improvement of falling film vertical absorbers. A testing device has been designed and built for reproducing absorption phenomena in vertical tubes with the primary objective to obtain experimental data in LiBr-H2O vertical absorbers. The versatility of the experiment allows to obtain a wide range of data.Large eddy simulation of hydrogen autoignition in a preheated turbulent co-flow
http://hdl.handle.net/2117/105026
Large eddy simulation of hydrogen autoignition in a preheated turbulent co-flow
Muela Castro, Jordi; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio; Ventosa Molina, Jordi
The autoignition process of a hydrogen jet into a preheated turbulent air stream is numerically studied. A Progress-variable (PV) model with the turbulence-chemistry interactions modelled using a Presumed Conditional Moment (PCM) closure has been used. Furthermore, the same case is studied using a Finite Rates model without closure for the reaction rate. The PV-PCM model reproduces satisfactorily the physical behaviour found in the experiments, although the model tends to underpredict the autoignition length. The results of the Finite Rates model also capture accurately the autoignition phenomenology observed experimentally and the autoignition lengths are closer to those obtained in the experiment.
2017-05-30T14:35:02ZMuela Castro, JordiLehmkuhl Barba, OriolOliva Llena, AsensioVentosa Molina, JordiThe autoignition process of a hydrogen jet into a preheated turbulent air stream is numerically studied. A Progress-variable (PV) model with the turbulence-chemistry interactions modelled using a Presumed Conditional Moment (PCM) closure has been used. Furthermore, the same case is studied using a Finite Rates model without closure for the reaction rate. The PV-PCM model reproduces satisfactorily the physical behaviour found in the experiments, although the model tends to underpredict the autoignition length. The results of the Finite Rates model also capture accurately the autoignition phenomenology observed experimentally and the autoignition lengths are closer to those obtained in the experiment.An OpenCL-based parallel CFD code for simulations on hybrid systems with massively-parallel accelerators
http://hdl.handle.net/2117/105006
An OpenCL-based parallel CFD code for simulations on hybrid systems with massively-parallel accelerators
Gorobets, Andrei; Trias Miquel, Francesc Xavier; Oliva Llena, Asensio
A parallel finite-volume CFD algorithm for modeling of incompressible flows on hybrid supercomputers is presented. It is based on
a symmetry-preserving high-order numerical scheme for structured meshes. A multilevel approach that combines di erent parallel
models is used for large-scale simulations on computing systems with massively-parallel accelerators. MPI is used on the first
level within the distributed memory model to couple computing nodes of a supercomputer. On the second level OpenMP is used to
engage multiple CPU cores of a computing node. The third level exploits the computing potential of massively-parallel accelerators
such as GPU (Graphics Processing Units) of AMD and NVIDIA, or Intel Xeon Phi accelerators of the MIC (Many Integrated Core)
architecture. The hardware independent OpenCL standard is used to compute on accelerators of di erent architectures within a
general model for a combination of a central processor and a math co-processor.
2017-05-29T14:55:57ZGorobets, AndreiTrias Miquel, Francesc XavierOliva Llena, AsensioA parallel finite-volume CFD algorithm for modeling of incompressible flows on hybrid supercomputers is presented. It is based on
a symmetry-preserving high-order numerical scheme for structured meshes. A multilevel approach that combines di erent parallel
models is used for large-scale simulations on computing systems with massively-parallel accelerators. MPI is used on the first
level within the distributed memory model to couple computing nodes of a supercomputer. On the second level OpenMP is used to
engage multiple CPU cores of a computing node. The third level exploits the computing potential of massively-parallel accelerators
such as GPU (Graphics Processing Units) of AMD and NVIDIA, or Intel Xeon Phi accelerators of the MIC (Many Integrated Core)
architecture. The hardware independent OpenCL standard is used to compute on accelerators of di erent architectures within a
general model for a combination of a central processor and a math co-processor.Parallel large eddy simulations of wind farms with the actuator line method
http://hdl.handle.net/2117/105005
Parallel large eddy simulations of wind farms with the actuator line method
Baez Vidal, Aleix; Lehmkuhl Barba, Oriol; Martínez Valdivieso, Daniel; Pérez Segarra, Carlos David
Parallel Computation of wind farm Large Eddy Simulations (LES) requires the use of with Wind Turbine Models (WTM). CFD and WTM demand different domain decompositions as optimal CFD and WTM decompositions do not necessarily coincide. Nevertheless, data exchange between CFD and WTM must not penalize overall simulation performance. A coupling strategy for data exchange is described and has been tested. It enables the parallel simulation of wind farms with WTM. Simulations of wind turbine wakes have been achieved. Preliminary results show the parallelization works properly but that the simulations do not resolve flows with enough accuracy.
2017-05-29T14:26:00ZBaez Vidal, AleixLehmkuhl Barba, OriolMartínez Valdivieso, DanielPérez Segarra, Carlos DavidParallel Computation of wind farm Large Eddy Simulations (LES) requires the use of with Wind Turbine Models (WTM). CFD and WTM demand different domain decompositions as optimal CFD and WTM decompositions do not necessarily coincide. Nevertheless, data exchange between CFD and WTM must not penalize overall simulation performance. A coupling strategy for data exchange is described and has been tested. It enables the parallel simulation of wind farms with WTM. Simulations of wind turbine wakes have been achieved. Preliminary results show the parallelization works properly but that the simulations do not resolve flows with enough accuracy.On the CFD&HT of the flow around a parabolic trough solar collector under real working conditions
http://hdl.handle.net/2117/105000
On the CFD&HT of the flow around a parabolic trough solar collector under real working conditions
Amine Hachicha, Ahmed; Rodríguez Pérez, Ivette María; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio
Parabolic trough solar collector is currently one of the most mature and prominent solar applications for production of electricity.
These systems are usually located in open terrain where strong winds may occur and affect their stability and optical performance, as well as, the heat exchange between the solar receiver and the ambient air. In this context, a wind flow analysis around a parabolic trough solar collector under real working conditions is performed. A numerical aerodynamic and heat transfer study based on Large Eddy Simulations is carried out to characterize the wind loads and the heat transfer coefficients.
Computations are performed for two Reynolds number ReW1=3.9×10^5 and ReW2=1×10^6 and various pitch angles. The effects of wind speed and pitch angle on the averaged and instantaneous flow have been assessed. The aerodynamic coefficients are calculated around the solar collectorand validated with measurements performed in wind tunnel tests. The variation of the heat transfer coefficient around the heat collector element with the Reynolds number is presented and compared to the circular cylinder in cross flow.
2017-05-29T12:24:14ZAmine Hachicha, AhmedRodríguez Pérez, Ivette MaríaLehmkuhl Barba, OriolOliva Llena, AsensioParabolic trough solar collector is currently one of the most mature and prominent solar applications for production of electricity.
These systems are usually located in open terrain where strong winds may occur and affect their stability and optical performance, as well as, the heat exchange between the solar receiver and the ambient air. In this context, a wind flow analysis around a parabolic trough solar collector under real working conditions is performed. A numerical aerodynamic and heat transfer study based on Large Eddy Simulations is carried out to characterize the wind loads and the heat transfer coefficients.
Computations are performed for two Reynolds number ReW1=3.9×10^5 and ReW2=1×10^6 and various pitch angles. The effects of wind speed and pitch angle on the averaged and instantaneous flow have been assessed. The aerodynamic coefficients are calculated around the solar collectorand validated with measurements performed in wind tunnel tests. The variation of the heat transfer coefficient around the heat collector element with the Reynolds number is presented and compared to the circular cylinder in cross flow.