Pinelli, Alfredo

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Universidad Complutense de Madrid
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Ciencias Matemáticas
Matemática Aplicada
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Now showing 1 - 5 of 5
  • Publication
    Block tridiagonal solvers on heterogeneous architectures
    (IEEE, 2012) Valero Lara, P.; Pinelli, Alfredo; Favier, J.; Matías, M.P.
    Modern multi-core and many-core systems offer a very impressive cost/performance ratio. In this paper a set of new parallel implementations for the solution of linear systems with block-tridiagonal coefficient matrix on current parallel architectures is proposed and evaluated: one of them on multi-core, others on many-core and finally, a new heterogeneous implementation on both architectures. The results show a speedup higher than 6 on certain parts of the problem, being the heterogeneous implementation the fastest.
  • Publication
    Control of the separated flow around an airfoil using a wavy leading edge inspired by humpback whale flippers
    (Elsevier France-editions Scientifiques Medicales Elsevier, 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.
  • Publication
    A fast Lagrangian tracking method capturing finite-size effects in particulate flows
    (American Physical Society, 2011) Wu, M.; Favier, J.; Pinelli, Alfredo
    We present a new method to capture the finite-size effects induced by particles transported by a fluid flow, with a low computational cost compared to available fully-resolved methods, thus allowing to tackle configurations with high volume fractions of particles. The basic idea consists in tracking a source/sink of momentum occurring within a compact support of the mesh, centered on the particle and taking the form of a mollified Dirac kernel, or blob. In the spirit of the immersed boundary method, the shape and the intensity of the kernel are found by imposing appropriate reproducing conditions on the blob (to model accurately a Dirac pulse) and spreading on the mesh cells a volume force determined by the desired boundary condition. The particles occupy a finite-size volume of fluid, therefore introducing a two-way coupled behavior, for the computational cost of only one Lagrangian point. To build the blobs, we will either spread a zero-velocity condition at the blob center, or spread a zero-velocity condition averaged on the fluid parcel enclosed within the support. Both methods are discussed and validated by comparing with free falling fully-resolved particles, in 2D and 3D.
  • Publication
    Immersed-boundary methods for general finite-difference and finite-volume Navier-Stokes solvers
    (Elsevier, 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.
  • Publication
    Interaction of multiple flapping filaments for cylinder wake modification using the Lattice Boltzmann Method
    (2012) Revell, A.; Favier, J.; Pinelli, Alfredo
    This 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.