Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3193
2015-07-30T10:21:04ZImprovements on the numerical analysis of viscoplastic-type non-Newtonian fluid flows
http://hdl.handle.net/2117/27318
Improvements on the numerical analysis of viscoplastic-type non-Newtonian fluid flows
Carmona Muñoz, Ángel; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David; Oliva Llena, Asensio
The aim of this work is to delve into the numerical analysis of viscoplastic-type non-Newtonian fluid flows with the objective of carrying out more advanced numerical simulations for them. Specifically, improvements in the spatial discretization schemes and the temporal integration methods are proposed to overcome the numerical problems introduced by the transpose diffusive term and associated with the velocity field discontinuity, the artificial viscous diffusion and the transpose viscous coupling.
2014-01-01T00:00:00ZSpectrally-consistent regularization of turbulent Rayleigh-Bénard convection
http://hdl.handle.net/2117/26901
Spectrally-consistent regularization of turbulent Rayleigh-Bénard convection
Dabbagh, Firas; Trias Miquel, Francesc Xavier; Gorobets, Andrei; Oliva Llena, Asensio
Direct numerical simulation (DNS) of turbulent Rayleigh-Bénard convection in an air filled (Pr = 0,7) rectangular cell of squared cross-section with periodic boundary conditions in the span-wise direction, has been carried out at Ra = 10^8. A fourth-order energy-conserving discretizations have been used that ensure non-physical dissipative effects introduced usually in other numerical schemes. The two sensitive fine-scales kinetic and thermal dissipation rates have been studied statistically to reveal high correlation within the thermal boundary layers and equilibrium zones of the two dissipations at strong thermal and kinetic interactions. It has been found that the foregoing zones could mark the plumes since these last reflect significant correlation regions of the kinetic and thermal fields. Afterwards, a novel class of symmetry-preserving regularization models that restrain the convective production of small scales of motion in unconditionally stable manner, have been applied on the studied problem. The obtained results are compared directly with the DNS ones to show a reasonable correspondence with and without model at this kind of moderate turbulence.
2014-01-01T00:00:00ZUnstructured 3D numerical modeling of the melting of a PCM contained in a spherical capsule
http://hdl.handle.net/2117/26897
Unstructured 3D numerical modeling of the melting of a PCM contained in a spherical capsule
Galione Klot, Pedro Andrés; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Pérez Segarra, Carlos David; Oliva Llena, Asensio
2014-01-01T00:00:00ZDirect numerical simulation of the flow over a spherical bubble in a turbulent pipe flow
http://hdl.handle.net/2117/26896
Direct numerical simulation of the flow over a spherical bubble in a turbulent pipe flow
Jofre Cruanyes, Lluís; Balcázar Arciniega, Néstor; Lehmkuhl Barba, Oriol; Borrell Pol, Ricard; Castro González, Jesús
This work aims at investigating, by means of a direct numerical simulation, the flow over a clean spherical bubble fixed on the axis of a turbulent pipe flow. The simulation is performed by means of a parallel unstructured symmetry-preserving formulation on a mesh of 5.4M cells. The main features of the turbulent flow are described by analyzing the time-averaged data collected over a significant period of time. The numerical results conclude that the bubble generates a wake, similarly to the case of a solid sphere, however, it differs in the fact that the fluid slips through the surface of the bubble instead of stopping, thus, no boundary layer is created. Moreover, due to viscosity, a transfer of momentum from the fluid surrounding the bubble to the fluid inside of it is produced. This transfer of momentum generates a turbulent toroidal vortex inside the bubble. In consequence, two short recirculation zones are found at the extremes of the bubble’s diameter, while in between, the axial velocity inverts its sign.
2014-01-01T00:00:00ZNumerical modeling of simultaneous heat and moisture transfer under complex geometry for refrigeration purposes
http://hdl.handle.net/2117/26805
Numerical modeling of simultaneous heat and moisture transfer under complex geometry for refrigeration purposes
Hou, Xiaofei; Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Oliet Casasayas, Carles; Pérez Segarra, Carlos David
The aim of the paper is to gain a better insight into heat and moisture transfer in refrigerator and to do fundamental study for water evaporation and condensation in refrigeration application. The governing transport equations (continuity, momentum, energy and concentration equations) in 3D Cartesian coordinates are firstly introduced. As the mixed convection is simulated in the paper, buoyancy forces caused by both temperature and concentration gradient are considered and are also included in momentum equation. Numerical results are carried out by using Termofluids code. The pressure-velocity linkage is solved by means of an explicit finite volume fractional step procedure. In order to validate the code, a humid air flowing in a horizontal 3D rectangular duct case is carried out and compared with the published numerical and experimental results. The contour of temperature and vapor density of air at a cross section is provided and analyzed. Finally, the heat and mass transfer process during the moist air flow through complicated geometry is simulated and temperature and humidity distributions are obtained.
2012-01-01T00:00:00ZOn the IBM approximation for the wheel aerodynamic simulation
http://hdl.handle.net/2117/26777
On the IBM approximation for the wheel aerodynamic simulation
Aljure Osorio, David E.; Lehmkuhl Barba, Oriol; Martínez Valdivieso, Daniel; Favre Samarra, Federico; Oliva Llena, Asensio
Challenging large eddy simulations (CLES) are performed to the flow around simplified wheels in wheelhouses. Wheel geometry is modelled using immersed boundary methods.
Results are compared to previous numerical simulations. Instantaneous flows results and turbulent structures are analysed to asses the viability of this boundary treatment on the resolution of a rotating wheel.
2014-01-01T00:00:00ZLarge eddy simulation of a turbulent jet diffusion flame using the Flamelet-Progress Variable model
http://hdl.handle.net/2117/22039
Large eddy simulation of a turbulent jet diffusion flame using the Flamelet-Progress Variable model
Ventosa, Jordi; Lehmkuhl Barba, Oriol; Pérez Segarra, Carlos David; Oliva Llena, Asensio
In this work an hydrogen enriched methane flame in a non-premixed configuration is studied, which corresponds to the DLR flame A. Large Eddy Simulation (LES) will be used to numerically analyse the case. Unstructured meshes are used and coupled with conservative discretisations of the differential operators. Chemical kinetics are modelled using the Flamelet/Progress-Variable model, taking into account differential diffusion effects. Computed first and second moments of the transported variables are shown to be in agreement with the experimental data.
2013-01-01T00:00:00ZStudy of the autoignition of a hydrogen jet in a turbulent co-flow of heated air using LES modelling
http://hdl.handle.net/2117/22038
Study of the autoignition of a hydrogen jet in a turbulent co-flow of heated air using LES modelling
Muela Castro, Jordi; Ventosa, Jordi; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio
The autoignition process of a hydrogen jet into a preheated turbulent air stream is numerically studied. A Progress-variable model with the turbulence-chemistry interaction s 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 also capture accurately the autoignition phenomenology observed experimentally and the autoignition lengths are closer to those obtained in the experiment.
2013-01-01T00:00:00ZLarge-eddy simulations of turbulent flow around a wall-mounted cube using an adaptive mesh refinement approach
http://hdl.handle.net/2117/22037
Large-eddy simulations of turbulent flow around a wall-mounted cube using an adaptive mesh refinement approach
Antepara Zambrano, Óscar; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio; Favre, Federico
In the present work two LES models for predicting turbulent flow and an Adaptive Mesh Refinement (AMR) technique are proposed and tested for a fully 3D geometry: turbulent flow around a wall-mounted cube at Reh=7235. The wall-adapting eddy viscosity model within a variational multiscale method (VMS-WALE) and the QR model are tested to predict the flow around the body. The numerical algorithm used to solve the governing equations preserves the symmetry and conservation properties. AMR algorithm is applied to get enough grid-resolution to solve the vortical structures near the body, adapting the mesh according to physics-based refinement criteria. High order conservative schemes are applied in the connection between coarse and fine regions. The numerical results obtained are assessed and compared to the results of the direct numerical simulations (DNS) on the basis of first and second order statistics.
2013-01-01T00:00:00ZBlending regularization and large-eddy simulation. From homogeneous isotropic turbulence to wind farm boundary layers
http://hdl.handle.net/2117/22034
Blending regularization and large-eddy simulation. From homogeneous isotropic turbulence to wind farm boundary layers
Folch Flórez, David; Trias Miquel, Francesc Xavier; Gorobets, Andrei; Oliva Llena, Asensio
The incompressible Navier-Stokes equations form an excellent mathematical model for turbulent flows. However, direct simulations at high Reynolds numbers are not feasible because the convective term produces far too many relevant scales of motion.
Therefore, in the foreseeable future numerical simulations of turbulent flows will have to resort to models of the small scales. Large-eddy simulation (LES) and regularization models are examples thereof. In the present work, we propose to combine both approaches.
Restoring the Galilean invariance of the regularization method results into an additional hyperviscosity term. This approach provides a natural blending between regularization and LES. The performance of these recent improvements will be assessed through application to homogeneous isotropic turbulence, a turbulent channel flow and a wind-farm turbulent boundary layer.
2013-01-01T00:00:00Z