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
36 results
Search Results
Now showing 1 - 10 of 36
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 The role of the forcing term in the large eddy simulation of equilibrium channel flow(Engineering Turbulence Modeling and Experiments, 1990) Benocci, C.; Pinelli, AlfredoItem Marginally turbulent flow in a square duct(Journal of fluid mechanics, 2007) Uhlmann, Markus; Pinelli, Alfredo; Kawahara, Genta; Sekimoto, AtshushiA direct numerical simulation of turbulent flow in a straight square duct was performed in order to determine the minimal requirements for self-sustaining turbulence. It was found that turbulence can be maintained for values of the bulk Reynolds number above approximately 1100, corresponding to a friction-velocity-based Reynolds number of 80. The minimum value for the streamwise period of the computational domain is around 190 wall units, roughly independently of the Reynolds number. We present a characterization of the flow state at marginal Reynolds numbers which substantially differs from the fully turbulent one: the marginal state exhibits a four-vortex secondary flow structure alternating in time whereas the fully turbulent one presents the usual eight-vortex pattern. It is shown that in the regime of marginal Reynolds numbers buffer-layer coherent structures play a crucial role in the appearance of secondary flow of Prandtl's second kind.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 Reynolds number dependence of mean flow structure in square duct turbulence - CORRIGENDUM(Journal of fluid mechanics, 2010) Pinelli, Alfredo; Uhlmann, Markus; Sekimoto, Atshushi; Kawahara, GentaItem Chebyshev collocation method and multidomain decomposition for the incompressible Navier‐Stokes equations(International journal for numerical methods in fluids, 1994) Pinelli, Alfredo; Vacca, A.The two-dimensional incompressible Navier-Stokes equations in primitive variables have been solved by a pseudospectral Chebyshev method using a semi-implicit fractional step scheme. The latter has been adapted to the particular features of spectral collocation methods to develop the monodomain algorithm. In particular, pressure and velocity collocated on the same nodes are sought in a polynomial space of the same order; the cascade of scalar elliptic problems arising after the spatial collocation is solved using finite difference preconditioning. With the present procedure spurious pressure modes do not pollute the pressure field. As a natural development of the present work a multidomain extent was devised and tested. The original domain is divided into a union of patching sub-rectangles. Each scalar problem obtained after spatial collocation is solved by iterating by subdomains. For steady problems a C1 solution is recovered at the interfaces upon convergence, ensuring a spectrally accurate solution. A number of test cases have been solved to validate the algorithm in both its single-block and multidomain configurations. The preliminary results achieved indicate that collocation methods in multidomain configurations might become a viable alternative to the spectral element technique for accurate flow prediction.Item Buoyancy effects on low-Reynolds-number turbulent flow in a horizontal square duct(Turbulence, Heat and Mass Transfer 6. Proceedings of the Sixth International Symposium On Turbulence, Heat and Mass Transfer - Rome, Italy, 14-18 September, 2009, 2009) Sekimoto, Atshushi; Sekiyama, K.; Kawahara, Genta; Uhlmann, Markus; Pinelli, AlfredoDirect numerical simulations of fully developed low-Reynolds-number turbulent flow in a horizontal square duct heated from below are performed at Richardson numbers 0 ≤ Ri ≤ 1.03 to investigate the buoyancy effects on the coherent structures near the walls, i.e. streamwise vortices and associated streaks, and on turbulence-driven secondary flow of Prandtl's second kind. It is found that cross-streamwise thermal convection which is represented by single large-scale circulation appears to affect the coherent structures and the mean secondary flow for Ri ≥ 0.02. As Ri is increased, the nearwall coherent structures are observed to appear more frequently in the region near one of the two corners on the wall, since they are swept along the wall towards the corner by the large-scale convection. The localization of the near-wall structures affects the profile of skin friction and heat transfer rate on the wall.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 A preconditioning technique for Chebyshev collocated advection diffusion operators(Computationa, Computational fluid dynamics' 92; Proceedings of the European Computational Fluid Dynamics Conference, 1st, Brussels, Belgium, Sep. 7-11, 1992, 1992) Pinelli, Alfredo; Benocci, C.; Deville, M.An original method for preconditioning Chebyshev collocated advection-diffusion operators is proposed. The preconditioner, based on an upwind finite difference approximation, is tested on one and two dimensional problems with both Neumann and Dirichlet boundary conditions.Item Performance of various fluid-solid coupling methods for DNS of particulate flow(IUTAM Symposium on Computational Approaches to Multiphase Flow, 2006) Uhlmann, Markus; Pinelli, Alfredo