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Paulo Zandonade

Bio: Paulo Zandonade is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Turbulence & Reynolds number. The author has an hindex of 6, co-authored 10 publications receiving 1142 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the spectra and correlations of the velocity fluctuations in turbulent channels, especially above the buffer layer, were analyzed using direct numerical simulations with friction Reynolds numbers up to Re at very large ones.
Abstract: The spectra and correlations of the velocity fluctuations in turbulent channels, especially above the buffer layer, are analysed using new direct numerical simulations with friction Reynolds numbers up to Re at very large ones.

717 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the organization of vortex clusters above the buffer layer of turbulent channels using direct numerical simulations at friction Reynolds numbers up to Re τ = 1900, where Re τ is the Reynolds number of vortex heads.
Abstract: The organization of vortex clusters above the buffer layer of turbulent channels is analysed using direct numerical simulations at friction Reynolds numbers up to Re τ = 1900. Especial attention is paid to a family of clusters that reach from the logarithmic layer to the near-wall region below y + = 20. These tall attached clusters are markers of structures of the turbulent fluctuating velocity that are more intense than their background. Their lengths and widths are proportional to their heights Ay and grow self-similarly with time after originating at different wall-normal positions in the logarithmic layer. Their influence on the outer region is measured by the variation of their volume density with Δ y . That influence depends on the vortex identification threshold, and becomes independent of the Reynolds number if the threshold is low enough. The clusters are parts of larger structures of the streamwise velocity fluctuations whose average geometry is consistent with a cone tangent to the wall along the streamwise axis. They form groups of a few members within each cone, with the larger individuals in front of the smaller ones. This behaviour is explained considering that the streamwise velocity cones are 'wakes' left behind by the clusters, while the clusters themselves are triggered by the wakes left by yet larger clusters in front of them. The whole process repeats self-similarly in a disorganized version of the vortex-streak regeneration cycle of the buffer layer, in which the clusters and the wakes spread linearly under the effect of the background turbulence. These results characterize for the first time the structural organization of the self-similar range of the turbulent logarithmic region.

389 citations

01 Nov 2003
TL;DR: In this article, the spectra and correlations of the velocity fluctuations in turbulent channels, especially above the buffer layer, were analyzed using direct numerical simulations with friction Reynolds numbers up to Re at very large ones.
Abstract: The spectra and correlations of the velocity fluctuations in turbulent channels, especially above the buffer layer, are analysed using new direct numerical simulations with friction Reynolds numbers up to Re at very large ones.

81 citations

Journal ArticleDOI
TL;DR: In this paper, the feasibility of an optimal finite-volume large-eddy simulation (LES) model for isotropic turbulence is evaluated, based on the approximation of the ideal LES by a stochastic estimate of the fluxes in a finite volume representation of the Navier-Stokes equation.
Abstract: The feasibility of an optimal finite-volume large-eddy simulation (LES) model for isotropic turbulence is evaluated. This modeling approach is based on the approximation of the ideal LES by a stochastic estimate of the fluxes in a finite-volume representation of the Navier–Stokes equation. Stochastic estimation of the fluxes allows for the simultaneous treatment of Navier–Stokes, discretization and subgrid effects, yielding a compact, yet accurate scheme for the large eddy simulation of isotropic turbulence. Both global and local models based on optimal finite-volume LES are developed and used in a priori tests guiding the choice of stencil geometry and model inputs. The most promising models in the a priori exams are tested in actual simulations (i.e., a posteriori) and the results compared with those for filtered direct numerical simulation (DNS) and the dynamic Smagorinsky model. The a posteriori performance of the optimal finite-volume LES models, evaluated by the energy spectrum and third-order struc...

38 citations

Journal ArticleDOI
TL;DR: In this article, it is shown that the Kolmogorov inertial range theory, along with an assumption of small-scale isotropy, the application of the quasinormal approximation and a mild modeling assumption regarding the three-point third-order correlation are sufficient to determine all the correlation data required for optimal large eddy simulation.
Abstract: Large eddy simulation (LES), in which the large scales of turbulence are simulated while the effects of the small scales are modeled, is an attractive approach for predicting the behavior of turbulent flows. However, there are a number of modeling and formulation challenges that need to be addressed for LES to become a robust and reliable engineering analysis tool. Optimal LES is a LES modeling approach developed to address these challenges. It requires multipoint correlation data as input to the modeling, and to date these data have been obtained from direct numerical simulations (DNSs). If optimal LES is to be generally useful, this need for DNS statistical data must be overcome. In this paper, it is shown that the Kolmogorov inertial range theory, along with an assumption of small-scale isotropy, the application of the quasinormal approximation and a mild modeling assumption regarding the three-point third-order correlation are sufficient to determine all the correlation data required for optimal LES m...

33 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a publisher's version of an article published in Journal of Fluid Mechanics © 2007 Cambridge University Press, Cambridge, UK. www.cambridge.edu.org/
Abstract: This is a publisher’s version of an article published in Journal of Fluid Mechanics © 2007 Cambridge University Press. www.cambridge.org/

1,197 citations

Journal ArticleDOI
TL;DR: The hairpin vortex paradigm of Theodorsen coupled with the quasistreamwise vortex paradigm have gained considerable support from multidimensional visualization using particle image velocimetry and direct numerical simulation experiments as discussed by the authors.
Abstract: Coherent structures in wall turbulence transport momentum and provide a means of producing turbulent kinetic energy. Above the viscous wall layer, the hairpin vortex paradigm of Theodorsen coupled with the quasistreamwise vortex paradigm have gained considerable support from multidimensional visualization using particle image velocimetry and direct numerical simulation experiments. Hairpins can autogenerate to form packets that populate a significant fraction of the boundary layer, even at very high Reynolds numbers. The dynamics of packet formation and the ramifications of organization of coherent structures (hairpins or packets) into larger-scale structures are discussed. Evidence for a large-scale mechanism in the outer layer suggests that further organization of packets may occur on scales equal to and larger than the boundary layer thickness.

1,176 citations

Journal ArticleDOI
TL;DR: In this article, a new numerical simulation of a turbulent channel in a large box at Reτ=2003 is described and briefly compared with simulations at lower Reynolds numbers and with experiments.
Abstract: A new numerical simulation of a turbulent channel in a large box at Reτ=2003 is described and briefly compared with simulations at lower Reynolds numbers and with experiments. Some of the fluctuation intensities, especially the streamwise velocity, do not scale well in wall units, both near and away from the wall. Spectral analysis traces the near-wall scaling failure to the interaction of the logarithmic layer with the wall. The present statistics can be downloaded from http://torroja.dmt.upm.es/ftp/channels. Further ones will be added to the site as they become available.

1,018 citations

Journal ArticleDOI
TL;DR: In this paper, a direct numerical simulation of incompressible channel flow at a friction Reynolds number of 5186 has been performed, and the flow exhibits a number of the characteristics of high-Reynolds-number wall-bounded turbulent flows.
Abstract: A direct numerical simulation of incompressible channel flow at a friction Reynolds number ( ) of 5186 has been performed, and the flow exhibits a number of the characteristics of high-Reynolds-number wall-bounded turbulent flows. For example, a region where the mean velocity has a logarithmic variation is observed, with von Karman constant . There is also a logarithmic dependence of the variance of the spanwise velocity component, though not the streamwise component. A distinct separation of scales exists between the large outer-layer structures and small inner-layer structures. At intermediate distances from the wall, the one-dimensional spectrum of the streamwise velocity fluctuation in both the streamwise and spanwise directions exhibits dependence over a short range in wavenumber . Further, consistent with previous experimental observations, when these spectra are multiplied by (premultiplied spectra), they have a bimodal structure with local peaks located at wavenumbers on either side of the range.

910 citations

01 Apr 1992
TL;DR: In this paper, the authors proposed a monotone integrated large eddy simulation approach, which incorporates a form of turbulence modeling applicable when the large-scale flows of interest are intrinsically time dependent, thus throwing common statistical models into question.
Abstract: Fluid dynamic turbulence is one of the most challenging computational physics problems because of the extremely wide range of time and space scales involved, the strong nonlinearity of the governing equations, and the many practical and important applications. While most linear fluid instabilities are well understood, the nonlinear interactions among them makes even the relatively simple limit of homogeneous isotropic turbulence difficult to treat physically, mathematically, and computationally. Turbulence is modeled computationally by a two-stage bootstrap process. The first stage, direct numerical simulation, attempts to resolve the relevant physical time and space scales but its application is limited to diffusive flows with a relatively small Reynolds number (Re). Using direct numerical simulation to provide a database, in turn, allows calibration of phenomenological turbulence models for engineering applications. Large eddy simulation incorporates a form of turbulence modeling applicable when the large-scale flows of interest are intrinsically time dependent, thus throwing common statistical models into question. A promising approach to large eddy simulation involves the use of high-resolution monotone computational fluid dynamics algorithms such as flux-corrected transport or the piecewise parabolic method which have intrinsic subgrid turbulence models coupled naturally to the resolved scales in the computed flow. The physical considerations underlying and evidence supporting this monotone integrated large eddy simulation approach are discussed.

849 citations