Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3193
Thu, 22 Feb 2018 13:05:11 GMT2018-02-22T13:05:11ZNumerical simulation of turbulence at lower costs: regularization modeling
http://hdl.handle.net/2117/111300
Numerical simulation of turbulence at lower costs: regularization modeling
Trias Miquel, Francesc Xavier; Gorobets, Andrei; Soria Guerrero, Manel; Oliva Llena, Asensio
This work is devoted to the development of efficient methods for the numerical
simulation of incompressible flows on modern supercomputers. Direct simulation
of the Navier-Stokes equations is nowadays an essential tool to provide new
insights into the physics of turbulence and indispensable data for the development of
better turbulence models. However, since DNS simulations at high Reynolds numbers
are not feasible because the convective term produces far too many scales of
motion, a dynamically less complex mathematical formulation is sought. In the quest
for such a formulation, we consider regularizations of the convective term that preserve
symmetry and conservation properties exactly. This yields a novel class of
regularizations that restrain the convective production of small scales of motion in an
unconditionally stable manner. In this way, the new set of equations is dynamically
less complex than the original Navier-Stokes equations, and therefore more amenable
to be numerically solved. The only additional ingredient is a self-adjoint linear filter
whose local filter length is determined from the requirement that vortex-stretching
must be stopped at the scale set by the grid. Here, the performance of the method is
tested by means of direct comparison with several DNS reference simulations.
Tue, 28 Nov 2017 18:09:36 GMThttp://hdl.handle.net/2117/1113002017-11-28T18:09:36ZTrias Miquel, Francesc XavierGorobets, AndreiSoria Guerrero, ManelOliva Llena, AsensioThis work is devoted to the development of efficient methods for the numerical
simulation of incompressible flows on modern supercomputers. Direct simulation
of the Navier-Stokes equations is nowadays an essential tool to provide new
insights into the physics of turbulence and indispensable data for the development of
better turbulence models. However, since DNS simulations at high Reynolds numbers
are not feasible because the convective term produces far too many scales of
motion, a dynamically less complex mathematical formulation is sought. In the quest
for such a formulation, we consider regularizations of the convective term that preserve
symmetry and conservation properties exactly. This yields a novel class of
regularizations that restrain the convective production of small scales of motion in an
unconditionally stable manner. In this way, the new set of equations is dynamically
less complex than the original Navier-Stokes equations, and therefore more amenable
to be numerically solved. The only additional ingredient is a self-adjoint linear filter
whose local filter length is determined from the requirement that vortex-stretching
must be stopped at the scale set by the grid. Here, the performance of the method is
tested by means of direct comparison with several DNS reference simulations.Numerical resolution in a PCM accumulator in cryogenic conditions
http://hdl.handle.net/2117/111298
Numerical resolution in a PCM accumulator in cryogenic conditions
Morales Ruíz, Sergio; Rigola Serrano, Joaquim; Castro González, Jesús; Oliva Llena, Asensio
A numerical study of the thermal and fluid-dynamic behaviour of the two-phase flow inside ducts working
under cryogenic conditions, coupled with the analysis of a phase change material PCM accumulator is
presented. The numerical analysis is based on: i) a one-dimensional and transient integration of the
conservative equations (mass, momentum and energy) in case of the fluid flow inside tubes, and ii) a twodimensional
and transient integration of the conservative equations in case of the PCM accumulator. The
discretization of the governing equations has been developed by means of the finite volume technique. The
discretized governing equations are solved using a Semi-Implicit Method for Pressure-Linked Equations
(SIMPLE). The two-fluid model has been used to simulate the two-phase flow phenomena inside tubes,
which is an inter-penetrating model capable to define the behavior of the velocity, the pressure, the
temperature and the distribution of each one of the phases (gas and liquid), separately. A group of
parameters, used in the numerical model proposed, are evaluated by means of empirical correlations, which
have been obtained from the technical literature in the cryogenic field. Numerical results of the whole system
are shown, where the temperature distribution of the fluid flow, the wall pipe, and the PCM accumulator are
presented
Tue, 28 Nov 2017 17:52:25 GMThttp://hdl.handle.net/2117/1112982017-11-28T17:52:25ZMorales Ruíz, SergioRigola Serrano, JoaquimCastro González, JesúsOliva Llena, AsensioA numerical study of the thermal and fluid-dynamic behaviour of the two-phase flow inside ducts working
under cryogenic conditions, coupled with the analysis of a phase change material PCM accumulator is
presented. The numerical analysis is based on: i) a one-dimensional and transient integration of the
conservative equations (mass, momentum and energy) in case of the fluid flow inside tubes, and ii) a twodimensional
and transient integration of the conservative equations in case of the PCM accumulator. The
discretization of the governing equations has been developed by means of the finite volume technique. The
discretized governing equations are solved using a Semi-Implicit Method for Pressure-Linked Equations
(SIMPLE). The two-fluid model has been used to simulate the two-phase flow phenomena inside tubes,
which is an inter-penetrating model capable to define the behavior of the velocity, the pressure, the
temperature and the distribution of each one of the phases (gas and liquid), separately. A group of
parameters, used in the numerical model proposed, are evaluated by means of empirical correlations, which
have been obtained from the technical literature in the cryogenic field. Numerical results of the whole system
are shown, where the temperature distribution of the fluid flow, the wall pipe, and the PCM accumulator are
presentedSimulaton of absorption of H2O in falling film of LiBr aqueous in vertical tubes in wavy regime
http://hdl.handle.net/2117/111296
Simulaton of absorption of H2O in falling film of LiBr aqueous in vertical tubes in wavy regime
García-Rivera, Eduardo; Castro González, Jesús; Farnós Baulenas, Joan; Oliva Llena, Asensio
A mathematical model of falling film absorption of H2O by LiBr aqueous solutions which considers
wavy regimes has been implemented. The model is semi-empirical, based on Navier Stokes
equations together with energy and mass species simplified under the boundary layer hypotheses.
The coupled equations are solved by means of finite difference method in a step by step procedure.
The wavy profile is introduced by solving Free Surface Deflection Equation in each grid step, the
smooth film thickness is recalculated in function of the amplitude value of the wave profile and the
mass absorbed. In order to validate the model developed, a comparison is performed with a simple
model based on empirical information for heat and mass transfer coefficients for laminar smooth a
wavy regimes. Numerical results are compared between smooth thickness film and wavy profile.
Tue, 28 Nov 2017 16:44:12 GMThttp://hdl.handle.net/2117/1112962017-11-28T16:44:12ZGarcía-Rivera, EduardoCastro González, JesúsFarnós Baulenas, JoanOliva Llena, AsensioA mathematical model of falling film absorption of H2O by LiBr aqueous solutions which considers
wavy regimes has been implemented. The model is semi-empirical, based on Navier Stokes
equations together with energy and mass species simplified under the boundary layer hypotheses.
The coupled equations are solved by means of finite difference method in a step by step procedure.
The wavy profile is introduced by solving Free Surface Deflection Equation in each grid step, the
smooth film thickness is recalculated in function of the amplitude value of the wave profile and the
mass absorbed. In order to validate the model developed, a comparison is performed with a simple
model based on empirical information for heat and mass transfer coefficients for laminar smooth a
wavy regimes. Numerical results are compared between smooth thickness film and wavy profile.Coupling CFD models of airflow with building simulation with an object-oriented and parallel infrastructure
http://hdl.handle.net/2117/111285
Coupling CFD models of airflow with building simulation with an object-oriented and parallel infrastructure
Damle, Rashmin; Lehmkuhl Barba, Oriol; Rodríguez Pérez, Ivette María; Oliva Llena, Asensio
Integrating CFD & HT models with the general building program raises the computational time of
building simulations as these simulations are usually performed over a period of one year. Within
this context, our aim is to couple a object-oriented modular building program with CFD & HT for
airflow and parallelize the simulation with numerous processors for reducing computational time.
Also the modular nature of the code will allow to resolve selective critical zones with CFD & HT
models while employing simple models for airflow in less critical zones. Thus, there are different
levels of modelling different rooms/elements of the building system depending on the requirements
of a specific case.
Tue, 28 Nov 2017 15:33:42 GMThttp://hdl.handle.net/2117/1112852017-11-28T15:33:42ZDamle, RashminLehmkuhl Barba, OriolRodríguez Pérez, Ivette MaríaOliva Llena, AsensioIntegrating CFD & HT models with the general building program raises the computational time of
building simulations as these simulations are usually performed over a period of one year. Within
this context, our aim is to couple a object-oriented modular building program with CFD & HT for
airflow and parallelize the simulation with numerous processors for reducing computational time.
Also the modular nature of the code will allow to resolve selective critical zones with CFD & HT
models while employing simple models for airflow in less critical zones. Thus, there are different
levels of modelling different rooms/elements of the building system depending on the requirements
of a specific case.Study of turbulent natural convection in a tall differentially heated cavity filled with either non-participating, participating grey and participating semigrey media
http://hdl.handle.net/2117/111281
Study of turbulent natural convection in a tall differentially heated cavity filled with either non-participating, participating grey and participating semigrey media
Capdevila Paramio, Roser; Lehmkuhl Barba, Oriol; Colomer Rey, Guillem; Pérez Segarra, Carlos David
Turbulent natural couvection in a tall differentially heated cavity of aspect ratio 5:1, filled with air under a Rayleigh number based on the height of 4.5.10(10), is studied numerically. Three different situations have been analysed. In the first one, the cavity is filled with a transparent medium. In the second one, the cavity is filled with a semigrey participating mixture, of air mid water vapour. In the List (me the cavity contains a grey participating gas. The turbulent flow is described by means of Large Eddy Simulation (LES) using symmetry-preserving discretizations. Simulations are compared with experimental data available in the literature and with Direct Numerical Simulations (DNS). Surface and gas radiation have been simulated using the Discrete Ordinates Method (DOM). The influence of radiation on fluid flow behaviour has been analysed.
Tue, 28 Nov 2017 15:19:08 GMThttp://hdl.handle.net/2117/1112812017-11-28T15:19:08ZCapdevila Paramio, RoserLehmkuhl Barba, OriolColomer Rey, GuillemPérez Segarra, Carlos DavidTurbulent natural couvection in a tall differentially heated cavity of aspect ratio 5:1, filled with air under a Rayleigh number based on the height of 4.5.10(10), is studied numerically. Three different situations have been analysed. In the first one, the cavity is filled with a transparent medium. In the second one, the cavity is filled with a semigrey participating mixture, of air mid water vapour. In the List (me the cavity contains a grey participating gas. The turbulent flow is described by means of Large Eddy Simulation (LES) using symmetry-preserving discretizations. Simulations are compared with experimental data available in the literature and with Direct Numerical Simulations (DNS). Surface and gas radiation have been simulated using the Discrete Ordinates Method (DOM). The influence of radiation on fluid flow behaviour has been analysed.Numerical solutions for the fluid flow and the heat transfer of viscoplastic-type non-Newtonian fluids
http://hdl.handle.net/2117/111280
Numerical solutions for the fluid flow and the heat transfer of viscoplastic-type non-Newtonian fluids
Carmona Muñoz, Ángel; Pérez Segarra, Carlos David; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio
The aim of this work is to provide numerical solutions for the fluid flow and the heat transfer generated in closed systems containing viscoplastic-type non-Newtonian fluids. A lid driven cavity (LDC) and a differentially heated cavity (DHC) are used as test cases. These numerical solutions can be an appropriate tool for verifying CFD codes which have been developed or adapted to deal with this kind of non-Newtonian fluids. In order to achieve this objective, an in-house CFD code has been implemented and correctly verified by the method of manufactured solutions and by some numerical solutions too. Furthermore, a high-performance CFD code (Termo Fluids S.L.) has been adapted and properly verified, by the corresponding numerical solutions, to deal with this kind of non-Newtonian fluids.
The viscoplastic behaviour of certain non-Newtonian fluids will be generated from a viscous stress which has been defined by a potential-type rheological law. The pseudoplastic and dilatant behaviours will be studied. On this matter, the influence of different physical aspects on the numerical simulations will be analysed, e.g. different exponent values in the potential-type rheological law and different values of the non-dimensional numbers. Moreover, the influence of different numerical aspects on the numerical simulations will also be analysed, e.g. unstructured meshes, conservative numerical schemes and more efficient and parallel algorithms and solvers.
Tue, 28 Nov 2017 15:09:41 GMThttp://hdl.handle.net/2117/1112802017-11-28T15:09:41ZCarmona Muñoz, ÁngelPérez Segarra, Carlos DavidLehmkuhl Barba, OriolOliva Llena, AsensioThe aim of this work is to provide numerical solutions for the fluid flow and the heat transfer generated in closed systems containing viscoplastic-type non-Newtonian fluids. A lid driven cavity (LDC) and a differentially heated cavity (DHC) are used as test cases. These numerical solutions can be an appropriate tool for verifying CFD codes which have been developed or adapted to deal with this kind of non-Newtonian fluids. In order to achieve this objective, an in-house CFD code has been implemented and correctly verified by the method of manufactured solutions and by some numerical solutions too. Furthermore, a high-performance CFD code (Termo Fluids S.L.) has been adapted and properly verified, by the corresponding numerical solutions, to deal with this kind of non-Newtonian fluids.
The viscoplastic behaviour of certain non-Newtonian fluids will be generated from a viscous stress which has been defined by a potential-type rheological law. The pseudoplastic and dilatant behaviours will be studied. On this matter, the influence of different physical aspects on the numerical simulations will be analysed, e.g. different exponent values in the potential-type rheological law and different values of the non-dimensional numbers. Moreover, the influence of different numerical aspects on the numerical simulations will also be analysed, e.g. unstructured meshes, conservative numerical schemes and more efficient and parallel algorithms and solvers.Three dimensional numerical simulations of combined conduction and radiation in transparent insulation material
http://hdl.handle.net/2117/111259
Three dimensional numerical simulations of combined conduction and radiation in transparent insulation material
Kessentini, Hamdi; Capdevila Paramio, Roser; Castro González, Jesús; Oliva Llena, Asensio
A coupled radiative and conductive three dimensional numerical model of transparent insulation
material (TIM) is presented and the simulation results are compared with experimental results
found in the literature. Since the studied TIM structure has the form of honeycomb that consists
of a cellular array of repetitive nature, we considered a single isolated cell with opaque and
adiabatic walls. The combined radiation and conduction heat transfer across the isolated cell is
treated by solving the energy equation coupled to the radiative transfer equation (RTE). For the
resolution of the RTE, the Finite Volume Method is used. The boundary conditions for the
intensity of radiation are considered as diffusely emitting, specularly reflecting opaque surfaces.
The detailed simulation of the TIM cells allows to obtain simplified correlations of the heat
losses through the TIM that then will be introduced into a general model of flat plate solar
collector with TIM.
Mon, 27 Nov 2017 18:21:02 GMThttp://hdl.handle.net/2117/1112592017-11-27T18:21:02ZKessentini, HamdiCapdevila Paramio, RoserCastro González, JesúsOliva Llena, AsensioA coupled radiative and conductive three dimensional numerical model of transparent insulation
material (TIM) is presented and the simulation results are compared with experimental results
found in the literature. Since the studied TIM structure has the form of honeycomb that consists
of a cellular array of repetitive nature, we considered a single isolated cell with opaque and
adiabatic walls. The combined radiation and conduction heat transfer across the isolated cell is
treated by solving the energy equation coupled to the radiative transfer equation (RTE). For the
resolution of the RTE, the Finite Volume Method is used. The boundary conditions for the
intensity of radiation are considered as diffusely emitting, specularly reflecting opaque surfaces.
The detailed simulation of the TIM cells allows to obtain simplified correlations of the heat
losses through the TIM that then will be introduced into a general model of flat plate solar
collector with TIM.Low Mach Navier-Stokes equations on unstructured meshes
http://hdl.handle.net/2117/111253
Low Mach Navier-Stokes equations on unstructured meshes
Ventosa Molina, Jordi; Chiva Segura, Jorge; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David; Oliva Llena, Asensio
Numerical methods for fluxes with strong
density variations but with speeds much lower
than the sound speed, known as low Mach
flows, present some particularities with respect to
incompressible formulations. Despite having similar
application ranges, incompressible formulations
using the Boussinesq approximation with constant
fluid properties cannot correctly describe fluxes with
high density variations. According to Gray and
Giorgini [1], use of the Boussinesq approximation
can be considered valid for variations of the density
up to 10% with respect to the mean value, so when
strong density variations are present, variable density
formulations are required. In the low Mach number
Navier-Stokes equations the velocity divergence is
not zero and acoustic waves are not considered. Also,
the pressure is split into a dynamic pressure and a
thermodynamic part. The latter is used to evaluate
the density, by means of the ideal gas state law.
Here will be presented an extension of an
incompressible pressure projection-type algorithm
(fractional-step) to simulate low Mach fluxes, using
a Runge-Kutta/Crank-Nicolson time integration
scheme, similar to the one presented by Najm
et al. [2] and Nicoud in [3]. The use of
a predictor-corrector substeps is related to the
instabilities introduced by the density time derivative
into the constant coefficient Poisson equation, as
reported in [2, 3]. The spatial discretisation is
performed by means of an unstructured finite volume
technique, using both the collocated formulation by
Felten [4] and the staggered formulation by Perot [5].
Finally, the algorithm is tested against benchmark
test cases, such as the differentially heated cavity
with large temperature differences and cases with
reactive fluxes.
Mon, 27 Nov 2017 15:21:43 GMThttp://hdl.handle.net/2117/1112532017-11-27T15:21:43ZVentosa Molina, JordiChiva Segura, JorgeLehmkuhl Barba, OriolPérez Segarra, Carlos DavidOliva Llena, AsensioNumerical methods for fluxes with strong
density variations but with speeds much lower
than the sound speed, known as low Mach
flows, present some particularities with respect to
incompressible formulations. Despite having similar
application ranges, incompressible formulations
using the Boussinesq approximation with constant
fluid properties cannot correctly describe fluxes with
high density variations. According to Gray and
Giorgini [1], use of the Boussinesq approximation
can be considered valid for variations of the density
up to 10% with respect to the mean value, so when
strong density variations are present, variable density
formulations are required. In the low Mach number
Navier-Stokes equations the velocity divergence is
not zero and acoustic waves are not considered. Also,
the pressure is split into a dynamic pressure and a
thermodynamic part. The latter is used to evaluate
the density, by means of the ideal gas state law.
Here will be presented an extension of an
incompressible pressure projection-type algorithm
(fractional-step) to simulate low Mach fluxes, using
a Runge-Kutta/Crank-Nicolson time integration
scheme, similar to the one presented by Najm
et al. [2] and Nicoud in [3]. The use of
a predictor-corrector substeps is related to the
instabilities introduced by the density time derivative
into the constant coefficient Poisson equation, as
reported in [2, 3]. The spatial discretisation is
performed by means of an unstructured finite volume
technique, using both the collocated formulation by
Felten [4] and the staggered formulation by Perot [5].
Finally, the algorithm is tested against benchmark
test cases, such as the differentially heated cavity
with large temperature differences and cases with
reactive fluxes.Direct numerical simulation of the turbulent natural convection flow in an open cavity of aspect ratio 4
http://hdl.handle.net/2117/111187
Direct numerical simulation of the turbulent natural convection flow in an open cavity of aspect ratio 4
Chiva Segura, Jorge; Lehmkuhl Barba, Oriol; Borrell Pol, Ricard; Oliva Llena, Asensio
In this paper, three-dimensional turbulent natural convection heat transfer in an open cavity with an
isothermal wall facing the overture has been studied. The aspect ratio chosen for the cavity has been 4 to complement
the studies by Trias et al. [1, 2] of closed cavities with the same aspect ratio. Direct numerical simulations
(DNS) of the cavity are presented and analyzed. Rayleigh numbers up to Ra = 1012 has been considered.
Fri, 24 Nov 2017 18:00:33 GMThttp://hdl.handle.net/2117/1111872017-11-24T18:00:33ZChiva Segura, JorgeLehmkuhl Barba, OriolBorrell Pol, RicardOliva Llena, AsensioIn this paper, three-dimensional turbulent natural convection heat transfer in an open cavity with an
isothermal wall facing the overture has been studied. The aspect ratio chosen for the cavity has been 4 to complement
the studies by Trias et al. [1, 2] of closed cavities with the same aspect ratio. Direct numerical simulations
(DNS) of the cavity are presented and analyzed. Rayleigh numbers up to Ra = 1012 has been considered.Large-eddy simulation of turbulent dynamic fluid-structure interaction
http://hdl.handle.net/2117/111178
Large-eddy simulation of turbulent dynamic fluid-structure interaction
Estruch Pérez, Olga; Lehmkuhl Barba, Oriol; Borrell Pol, Ricard; Pérez Segarra, Carlos David
Fri, 24 Nov 2017 16:29:36 GMThttp://hdl.handle.net/2117/1111782017-11-24T16:29:36ZEstruch Pérez, OlgaLehmkuhl Barba, OriolBorrell Pol, RicardPérez Segarra, Carlos David