Person: Pinelli, Alfredo
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First Name
Alfredo
Last Name
Pinelli
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Matemáticas
Department
Area
Matemática Aplicada
Identifiers
25 results
Search Results
Now showing 1 - 10 of 25
Item Toward direct numerical simulation of reacting fluidized beds(Proceedings of the 3rd European Combustion Meeting, 2003) Uhlmann, Markus; Pinelli, Alfredo; GarcÃa Ybarra, P. L.Nowadays, the most used techniques to design dense gas-solid flow reactors rely upon numerical predictions obtained from hydrodynamic models, usually derived through some averaging processes of the complete conservation equations. The averaging process leads to unknown correlation terms that need further modeling for the final closure of the equations. Many of these terms represent complex interactions between phases and are usually modeled through semi-empirical relations. Direct Numerical Simulation (DNS) of idealized situations can help in grasping the basic mechanisms governing these systems, therefore fostering the development of improved models.Item Two-dimensional thermal convection flow with variable viscosity and embedded boundaries(2003) Uhlmann, Markus; Pinelli, AlfredoA two-dimensional model capable of simulating thermal convection flow in complex geometries has been implemented in a finite-difference setting and using a fictitious domain method of type “direct explicit forcing". The Boussinesq approximation is supposed to hold; the coupling between velocity and temperature fields is explicit; spatially varying viscosity is accounted for. The computation of a model for the thermally-induced flow in a three-chamber fuel tank reveals that the present method does not allow for sufficiently large time steps when the viscosity varies strongly.Item Interaction of multiple flapping filaments for cylinder wake modification using the Lattice Boltzmann Method(ICCFD7 : International Conference On Computational Fluid Dynamics, July 9-13, 2012, Mauna Lani Bay Hotel, Island of Hawaii, 2012) Revell, A.; Favier, J.; Pinelli, AlfredoThis paper introduces the recent work undertaken on the development of a code based on the combination of the Lattice Boltzmann Method (LBM) with a recent version of the Immersed Boundary Method (IBM). The code is first validated against existing results, before being applied to investigate the different modes of flapping behaviour for single and multiple filaments at various separation distances. The work proceeds to investigate the cylinder wake modification for moderate Reynolds number when groups of said filaments are attached to the ley-side of a circular cylinder.Item The instability of streaks in near-wall turbulence(Center for Turbulence Research, Annual Research Briefs, 1998) Kawahara, Genta; Jiménez, Javier; Uhlmann, Markus; Pinelli, AlfredoItem Control of the separated flow around an airfoil using a wavy leading edge inspired by humpback whale flippers(Comptes rendus. Mécanique, 2012) Favier, J.; Pinelli, Alfredo; Piomelli, U.The influence of spanwise geometrical undulations of the leading edge of an infinite wing is investigated numerically at low Reynolds number, in the context of passive separation control and focusing on the physical mechanisms involved. Inspired by the tubercles of the humpback whale flippers, the wavy leading edge is modeled using a spanwise sinusoidal function whose amplitude and wavelength constitute the parameters of control. A direct numerical simulation is performed on a NACA0020 wing profile in a deep stall configuration (α=20°), with and without the presence of the leading edge waviness. The complex solid boundaries obtained by varying the sinusoidal shape of the leading edge are modeled using an immersed boundary method (IBM) recently developed by the authors [Pinelli et al., J. Comput. Phys. 229 (2010) 9073–9091]. A particular set of wave parameters is found to change drastically the topology of the separated zone, which becomes dominated by streamwise vortices generated from the sides of the leading edge bumps. A physical analysis is carried out to explain the mechanism leading to the generation of these coherent vortical structures. The role they play in the control of boundary layer separation is also investigated, in the context of the modifications of the hydrodynamic performances which have been put forward in the literature in the last decade.Item Turbulent channel flow concentration profile and wall deposition of a large Schmidt number passive scalar(Comptes rendus. Mécanique, 2006) GarcÃa Ybarra, P. L.; Pinelli, AlfredoThe transport of a passive scalar within a turbulent plane channel flow has been theoretically analyzed by assuming that the Schmidt number Sc, associated to the molecular diffusivity of the passive scalar, is a large parameter. Throughout most of the channel cross-section the mean passive scalar density is constant, but adjacent to the walls a thin boundary layer develops embedded in the viscous sublayer, with a relative thickness of order Sc(-1/3). In this narrow region a passive scalar profile arises due to the non-vanishing flux normal to the wall. This profile is parameter independent (universal) and leads to a constant flux of passive scalar that results from the addition of both the molecular diffusion flux and the turbulent transport one. The Sc-asymptotic matching of this profile with the constant core value provides an analytical expression for the wall-normal flux that depends on the fluid dynamics of the carrier flow. By using a DNS code to solve the external turbulent flow, the analytical expression has been quantified and compared with empifical expressions based on experimental data, showing excellent agreement.Item Immersed-boundary methods for general finite-difference and finite-volume Navier-Stokes solvers(Journal of Computational Physics, 2010) Pinelli, Alfredo; Naqavi, I.Z.; Piomelli, U.; Favier, J.We present an immersed-boundary algorithm for incompressible flows with complex boundaries, suitable for Cartesian or curvilinear grid system. The key stages of any immersed-boundary technique are the interpolation of a velocity field given on a mesh onto a general boundary (a line in 2D, a surface in 3D), and the spreading of a force field from the immersed boundary to the neighboring mesh points, to enforce the desired boundary conditions on the immersed-boundary points. We propose a technique that uses the Reproducing Kernel Particle Method [W.K. Liu, S. Jun, Y.F. Zhang, Reproducing kernel particle methods, Int. J. Numer. Methods Fluids 20(8) (1995) 1081-1106] for the interpolation and spreading. Unlike other methods presented in the literature, the one proposed here has the property that the integrals of the force field and of its moment on the grid are conserved, independent of the grid topology (uniform or non-uniform, Cartesian or curvilinear). The technique is easy to implement, and is able to maintain the order of the original underlying spatial discretization. Applications to two- and three-dimensional flows in Cartesian and non-Cartesian grid system, with uniform and non-uniform meshes are presented.Item Characterisation of marginally turbulent square duct flow(Advances in Turbulence XI, 2007) Uhlmann, Markus; Pinelli, Alfredo; Sekimoto, Atshushi; Kawahara, Genta; Palma, J.L.M.L.; Silva Lopes, A.Item Immersed boundary method for generalised finite volume and finite difference Navier-Stokes solvers(ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting, 2010) Pinelli, Alfredo; Naqavi, I.Z.; Piomelli, U.In Immersed Boundary Methods (IBM) the effect of complex geometries is introduced through the forces added in the Navier-Stokes solver at the grid points in the vicinity of the immersed boundaries. Most of the methods in the literature have been used with Cartesian grids. Moreover many of the methods developed in the literature do not satisfy some basic conservation properties (the conservation of torque, for instance) on non-uniform meshes. In this paper we will follow the RKPM method originated by Liu et al. [1] to build locally regularized functions that verify a number of integral conditions. These local approximants will be used both for interpolating the velocity field and for spreading the singular force field in the framework of a pressure correction scheme for the incompressible Navier-Stokes equations. We will also demonstrate the robustness and effectiveness of the scheme through various examples.Item LES and RANS simulations of the MUST experiment. Study of incident wind direction effects on the flow and plume dispersion(7th International Conference on Urban Climate, 2007) Santiago, J. L.; Dejoan, A.; Martilli, A.; MartÃn , F.; Pinelli, AlfredoIn this study, we propose to assess and compare the performance of LES and RANS methodologies for the simulation of pollutant dispersion in an urban environment by making use of field and wind tunnel measurements of the MUST experiment configuration. First, the proposed analysis addresses the relevance of taking into account the small geometrical irregularities of the obstacle array in the computations. For this, local and spatial averaged time mean flow properties are compared for two geometries, one with a perfect alignment of the containers and another one including the irregularities present in the experiment. In both geometries the incident flow is orthogonal to the front array of obstacles. The second part of this study presents simulations with different approaching wind directions to analyse the effect of small changes in the incident wind direction on the flow and on the plume dispersion. In this second part, the mean concentration field is compared with the experimental data and an analysis that relates the channelling effects with the plume deflection is provided.