CTTC  Centre Tecnològic de la Transferència de Calor
http://hdl.handle.net/2117/3190
Wed, 26 Jul 2017 01:03:49 GMT
20170726T01:03:49Z

An eulerianlagrangian modeling of fluidized bed
http://hdl.handle.net/2117/106316
An eulerianlagrangian modeling of fluidized bed
Zhang, Hao; YuanQiang, Tan; DongMin, Yang; Trias Miquel, Francesc Xavier; Sheng, Yong; Oliva Llena, Asensio
The particle motions in a fluidized bed were numerically simulated using a EulerianLagrangian model.
The solid phase was modelled via the Discrete Element Method (DEM) while the hydrodynamic model of the fluid
phase was based on the volumeaveraged NavierStokes equations. A fluid densitybased buoyancy (FDB) model was
adopted to calculate the solidfluid interaction force. In this paper, the complex ‘four way coupled’ interaction as
proposed by Elghobashi in 1991 was modelled, namely the dominant effect of gas phase on the dispersed particles,
the back influence of the particle phase on the gas phase, and interactions between particles such as collision,
agglomeration and breakup. A stable succession of bubble formation and disappearance was captured. Obtained
pressure drop and interparticle contact number had a good agreement with those reported in previous reference
Mon, 10 Jul 2017 11:03:07 GMT
http://hdl.handle.net/2117/106316
20170710T11:03:07Z
Zhang, Hao
YuanQiang, Tan
DongMin, Yang
Trias Miquel, Francesc Xavier
Sheng, Yong
Oliva Llena, Asensio
The particle motions in a fluidized bed were numerically simulated using a EulerianLagrangian model.
The solid phase was modelled via the Discrete Element Method (DEM) while the hydrodynamic model of the fluid
phase was based on the volumeaveraged NavierStokes equations. A fluid densitybased buoyancy (FDB) model was
adopted to calculate the solidfluid interaction force. In this paper, the complex ‘four way coupled’ interaction as
proposed by Elghobashi in 1991 was modelled, namely the dominant effect of gas phase on the dispersed particles,
the back influence of the particle phase on the gas phase, and interactions between particles such as collision,
agglomeration and breakup. A stable succession of bubble formation and disappearance was captured. Obtained
pressure drop and interparticle contact number had a good agreement with those reported in previous reference

Advanced CFD&HT numerical modeling of solar tower receivers
http://hdl.handle.net/2117/106302
Advanced CFD&HT numerical modeling of solar tower receivers
Colomer Rey, Guillem; Chiva Segura, Jorge; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio
This paper presents an advanced methodology for the detailed modeling of the heat transfer and fluid dynamics phenomena in solar tower receivers. It has been carried out in the framework of a more ambitious enterprise which aims at modeling all the complex heat transfer and fluid dynamics phenomena present in central solar receivers. The global model is composed of 4 submodels (heat conduction, twophase flow, thermal radiation and natural convection) which are described.
Mon, 10 Jul 2017 09:29:58 GMT
http://hdl.handle.net/2117/106302
20170710T09:29:58Z
Colomer Rey, Guillem
Chiva Segura, Jorge
Lehmkuhl Barba, Oriol
Oliva Llena, Asensio
This paper presents an advanced methodology for the detailed modeling of the heat transfer and fluid dynamics phenomena in solar tower receivers. It has been carried out in the framework of a more ambitious enterprise which aims at modeling all the complex heat transfer and fluid dynamics phenomena present in central solar receivers. The global model is composed of 4 submodels (heat conduction, twophase flow, thermal radiation and natural convection) which are described.

Numerical study of Taylor bubbles rising in a stagnant liquid using a levelset/movingmesh method
http://hdl.handle.net/2117/105970
Numerical study of Taylor bubbles rising in a stagnant liquid using a levelset/movingmesh method
Gutiérrez González, Ernesto; Balcázar Arciniega, Néstor; Bartrons Casademont, Eduard; Rigola Serrano, Joaquim
An Arbitrary LagrangianEulerian formulation has been posed to solve the challenging problem of the threedimensional Taylor bubble, within a Conservative Level Set (CLS) framework. By employing a domain optimization method (i.e. the moving mesh method), smaller domains can be used to simulate rising bubbles, thus saving computational resources. As the method requires the use of open boundaries, a careful treatment of both inflow and outflow boundary conditions has been carried out. The coupled CLS  moving mesh method has been verified by means of extensive numerical tests. The challenging problem of the full threedimensional Taylor bubble has then been thoroughly addressed, providing a detailed description of its features. The study also includes a sensitivity analyses with respect to the initial shape of the bubble, the initial volume of the bubble, the flow regime and the inclination of the channel.
Thu, 29 Jun 2017 08:29:59 GMT
http://hdl.handle.net/2117/105970
20170629T08:29:59Z
Gutiérrez González, Ernesto
Balcázar Arciniega, Néstor
Bartrons Casademont, Eduard
Rigola Serrano, Joaquim
An Arbitrary LagrangianEulerian formulation has been posed to solve the challenging problem of the threedimensional Taylor bubble, within a Conservative Level Set (CLS) framework. By employing a domain optimization method (i.e. the moving mesh method), smaller domains can be used to simulate rising bubbles, thus saving computational resources. As the method requires the use of open boundaries, a careful treatment of both inflow and outflow boundary conditions has been carried out. The coupled CLS  moving mesh method has been verified by means of extensive numerical tests. The challenging problem of the full threedimensional Taylor bubble has then been thoroughly addressed, providing a detailed description of its features. The study also includes a sensitivity analyses with respect to the initial shape of the bubble, the initial volume of the bubble, the flow regime and the inclination of the channel.

Towards a direct numerical simulation of a lifted CH4air diffusion flame
http://hdl.handle.net/2117/105953
Towards a direct numerical simulation of a lifted CH4air diffusion flame
Ventosa Molina, Jordi; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David; Oliva Llena, Asensio
The near field jet of a selfigniting methaneair diffusion jet flame is studied by means of Direct Numerical Simulation (DNS) and a Flamelet/ProgressVariable (FPV) model to include detailed chemistry. Hence, all flow and transport scales are resolved and chemical reactions are assumed to take place in thin layers. Key aspects in the creation of the flamelet database, prior to the DNS simulation, are considered. Inclusion of differential diffusion effects are discussed by analysing the Sshaped curve and autoignition delay times. Similarly, the influence on these parameters of two detailed mechanism, the GRI2.11 and GRI3.0, is assessed. The definition of the progressvariable used in the FPV is analysed and a new definition is proposed. Results of the near jet, up to 20 jet diameters, are shown for the two detailed mechanism.
Wed, 28 Jun 2017 14:21:19 GMT
http://hdl.handle.net/2117/105953
20170628T14:21:19Z
Ventosa Molina, Jordi
Lehmkuhl Barba, Oriol
Pérez Segarra, Carlos David
Oliva Llena, Asensio
The near field jet of a selfigniting methaneair diffusion jet flame is studied by means of Direct Numerical Simulation (DNS) and a Flamelet/ProgressVariable (FPV) model to include detailed chemistry. Hence, all flow and transport scales are resolved and chemical reactions are assumed to take place in thin layers. Key aspects in the creation of the flamelet database, prior to the DNS simulation, are considered. Inclusion of differential diffusion effects are discussed by analysing the Sshaped curve and autoignition delay times. Similarly, the influence on these parameters of two detailed mechanism, the GRI2.11 and GRI3.0, is assessed. The definition of the progressvariable used in the FPV is analysed and a new definition is proposed. Results of the near jet, up to 20 jet diameters, are shown for the two detailed mechanism.

A finitevolume/levelset interface capturing method for unstructured grids: Simulations of bubbles rising through viscous liquids
http://hdl.handle.net/2117/105758
A finitevolume/levelset 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 twophase flows with moving interphase boundaries, which is integrated in a finitevolume 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.
Fri, 23 Jun 2017 09:33:15 GMT
http://hdl.handle.net/2117/105758
20170623T09:33:15Z
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 twophase flows with moving interphase boundaries, which is integrated in a finitevolume 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 liquidgas 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 finitevolume mesh discretizations suitable for threedimensional 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.
Fri, 23 Jun 2017 09:31:59 GMT
http://hdl.handle.net/2117/105755
20170623T09:31:59Z
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 liquidgas 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 finitevolume mesh discretizations suitable for threedimensional 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.

A 3D volumeoffluid advection method based on cellvertex velocities for unstructured meshes
http://hdl.handle.net/2117/105736
A 3D volumeoffluid advection method based on cellvertex velocities for unstructured meshes
Jofre Cruanyes, Lluís; Lehmkuhl Barba, Oriol; Castro González, Jesús; Oliva Llena, Asensio
A new geometrical VolumeofFluid (VOF) method for capturing interfaces on threedimensional (3D) Cartesian and unstructured meshes is introduced. The method reconstructs interfaces as first and secondorder piecewise planar approximations (PLIC), and advects volumes in a single unsplit Lagrangian–Eulerian (LE) geometrical algorithm based on constructing flux polyhedrons by tracing back the Lagrangian trajectories of the cellvertex velocities. In this way, the situations of overlapping between flux polyhedrons are minimized, consequently, the accuracy in the solution of the advection equation is improved by minimizing the creation of overshoots (volume fractions over one), undershoots (volume fractions below zero) and wisps (fluid in void regions or vice versa). However, if not treated carefully, the use of cellvertex velocities may result in the construction of flux polyhedrons that contain nonplanar faces and that do not conserve volume. Therefore, this work explains in detail a set of geometric algorithms necessary to overcome these two drawbacks. In addition, the new VOF method is analyzed numerically on 3D Cartesian and unstructured meshes, first, by reconstructing the interface of spherical geometries and, second, by evaluating the final advection result of a sphere placed in a rotation, shear and deformation field.
Thu, 22 Jun 2017 14:39:33 GMT
http://hdl.handle.net/2117/105736
20170622T14:39:33Z
Jofre Cruanyes, Lluís
Lehmkuhl Barba, Oriol
Castro González, Jesús
Oliva Llena, Asensio
A new geometrical VolumeofFluid (VOF) method for capturing interfaces on threedimensional (3D) Cartesian and unstructured meshes is introduced. The method reconstructs interfaces as first and secondorder piecewise planar approximations (PLIC), and advects volumes in a single unsplit Lagrangian–Eulerian (LE) geometrical algorithm based on constructing flux polyhedrons by tracing back the Lagrangian trajectories of the cellvertex velocities. In this way, the situations of overlapping between flux polyhedrons are minimized, consequently, the accuracy in the solution of the advection equation is improved by minimizing the creation of overshoots (volume fractions over one), undershoots (volume fractions below zero) and wisps (fluid in void regions or vice versa). However, if not treated carefully, the use of cellvertex velocities may result in the construction of flux polyhedrons that contain nonplanar faces and that do not conserve volume. Therefore, this work explains in detail a set of geometric algorithms necessary to overcome these two drawbacks. In addition, the new VOF method is analyzed numerically on 3D Cartesian and unstructured meshes, first, by reconstructing the interface of spherical geometries and, second, by evaluating the final advection result of a sphere placed in a rotation, shear and deformation field.

A lowdissipation convection scheme for the stable discretization of turbulent interfacial flow
http://hdl.handle.net/2117/105415
A lowdissipation convection scheme for the stable discretization of turbulent interfacial flow
Schillaci, Eugenio; Jofre Cruanyes, Lluís; Balcázar Arciniega, Néstor; Antepara Zambrano, Óscar; Oliva Llena, Asensio
This paper analyzes a lowdissipation discretization for the resolution of immiscible, incompressible multiphase flow by means of interfacecapturing schemes. The discretization is built on a threedimensional, unstructured finitevolume framework and aims at minimizing the differences in kinetic energy preservation with respect to the continuous governing equations. This property plays a fundamental role in the case of flows presenting significant levels of turbulence. At the same time, the hybrid form of the convective operator proposed in this work incorporates localized lowdispersion characteristics to limit the growth of spurious flow solutions. The lowdissipation discrete framework is presented in detail and, in order to expose the advantages with respect to commonly used methodologies, its conservation properties and accuracy are extensively studied, both theoretically and numerically. Numerical tests are performed by considering a threedimensional vortex, an exact sinusoidal function, and a spherical drop subjected to surface tension forces in equilibrium and immersed in a swirling velocity field. Finally, the turbulent atomization of a liquidgas jet is numerically analyzed to further assess the capabilities of the method.
© 2017. This version is made available under the CCBYNCND 4.0 license http://creativecommons.org/licenses/byncnd/4.0/
Wed, 14 Jun 2017 12:46:47 GMT
http://hdl.handle.net/2117/105415
20170614T12:46:47Z
Schillaci, Eugenio
Jofre Cruanyes, Lluís
Balcázar Arciniega, Néstor
Antepara Zambrano, Óscar
Oliva Llena, Asensio
This paper analyzes a lowdissipation discretization for the resolution of immiscible, incompressible multiphase flow by means of interfacecapturing schemes. The discretization is built on a threedimensional, unstructured finitevolume framework and aims at minimizing the differences in kinetic energy preservation with respect to the continuous governing equations. This property plays a fundamental role in the case of flows presenting significant levels of turbulence. At the same time, the hybrid form of the convective operator proposed in this work incorporates localized lowdispersion characteristics to limit the growth of spurious flow solutions. The lowdissipation discrete framework is presented in detail and, in order to expose the advantages with respect to commonly used methodologies, its conservation properties and accuracy are extensively studied, both theoretically and numerically. Numerical tests are performed by considering a threedimensional vortex, an exact sinusoidal function, and a spherical drop subjected to surface tension forces in equilibrium and immersed in a swirling velocity field. Finally, the turbulent atomization of a liquidgas jet is numerically analyzed to further assess the capabilities of the method.

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 inhouse implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a threedimensional explicit finite volume fractionalstep algorithm formulated in a secondorder, 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.
Mon, 05 Jun 2017 15:51:50 GMT
http://hdl.handle.net/2117/105134
20170605T15:51:50Z
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 inhouse implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a threedimensional explicit finite volume fractionalstep algorithm formulated in a secondorder, 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 waterice 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 waterice 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 inspace 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 phasechange models carried out by the ISP1 partner institution UPC [7], [8], [9].
Thu, 01 Jun 2017 15:05:50 GMT
http://hdl.handle.net/2117/105102
20170601T15:05:50Z
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 inspace 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 phasechange models carried out by the ISP1 partner institution UPC [7], [8], [9].