Search results for "Stokes"

An improved immersed boundary method for curvilinear grids

2009

Abstract In the present paper we propose an extension of the direct-forcing immersed boundary technique, recently developed and employed by Verzicco and co-authors [Fadlun EA, Verzicco R, Orlandi P, Mohd-Yusof J. Combined immersed-boundary finite-difference methods for three-dimensional complex flow simulations. J Comput Phys 2000;161:35–60; Verzicco R, Fatica M, Iaccarino G, Moin P, Khalighi B. Large eddy simulation of a road vehicle with drag-reduction devices. AIAA J 2002;40(12):2447–55; Cristallo A, Verzicco R. Combined immersed boundary/large-eddy-simulations of incompressible three-dimensional complex flows. Flow Turbul Combust 2006;77(1–4):3–26.] and successively improved by Balaras …

Adaptive control of a seven mode truncation of the Kolmogorov flow with drag

2009

Abstract We study a seven dimensional nonlinear dynamical system obtained by a truncation of the Navier–Stokes equations for a two dimensional incompressible fluid with the addition of a linear term modelling the drag friction. We show the bifurcation sequence leading from laminar steady states to chaotic solutions with increasing Reynolds number. Finally, we design an adaptive control which drives the state of the system to the equilibrium point representing the stationary solution.

High Reynolds number Navier-Stokes solutions and boundary layer separation induced by a rectilinear vortex

2013

Abstract We compute the solutions of Prandtl’s and Navier–Stokes equations for the two dimensional flow induced by a rectilinear vortex interacting with a boundary in the half plane. For this initial datum Prandtl’s equation develops, in a finite time, a separation singularity. We investigate the different stages of unsteady separation for Navier–Stokes solution at different Reynolds numbers Re = 103–105, and we show the presence of a large-scale interaction between the viscous boundary layer and the inviscid outer flow. We also see a subsequent stage, characterized by the presence of a small-scale interaction, which is visible only for moderate-high Re numbers Re = 104–105. We also investi…

The natural compound chrysosplenol-D is a novel, ultrasensitive optical sensor for detection of Cu(II)

2020

Abstract Herein, we introduce a novel, ultrasensitive optical sensor for determination of Cu(II) ions over the concentration range of 0 to 1 μM Cu(II). The optical sensor is based on the natural molecule chrysosplenol-D (Chp-D) extracted from the flowering plant Chiliadenus montanus (Vahl.) Brullo. Free Chp-D emits fluorescence at 566 nm when excited at 292 nm. Chp-D chelates Cu(II) ions to form a 1:1 (metal:ligand) complex, which quenches the fluorescence emission peak of the free probe at 566 nm. “Turn-off” luminescence could be easily determined and provided distinct proof of the chelation of Cu(II) ions by Chp-D. This novel optical sensor offers a considerable fluorescence mechanism (ch…

The Riesz Representation Theorem and Extension of Vector Valued Additive Measures

2001

Contrôle quantique adiabatique : technique de passage adiabatique parallèle et systèmes dissipatifs

2011

The first part of this thesis is devoted to the theoretical analysis of adiabatic processes allowing the transfer of population from an initial state to a target state of a quantum system. The strategy of parallel adiabatic passage, in which the coupling parameters are specifically designed to optimize the adiabatic passage corresponding to parallel eigenvalues at all times, allows one to combine the energetically efficiency of pi-pulse and related strategies with the robustness of standard adiabaticpassage. The second part of this thesis concerns the effects of the dissipation in adiabatic passage. The non-adiabatic transition probability formula of a two state system with dissipation is e…

High resolution CARS spectrum and analysis of the v1bandQ-branch of carbon dioxide

1988

High resolution coherent anti-Stokes Raman spectroscopy (CARS) has been applied to the study of the Q-branch of the fundamental vibrational v 1 band of CO2 in the Fermi resonance region near 1285·5 cm-1. Thanks to the use of high spectral quality (linewidth = 6 MHz) injection-locked flashlamp-pumped dye lasers, it was possible to resolve this band for the first time. The spectrum was recorded at a pressure of 5 kPa (37·5 Torr) at room temperature. We measured the line positions and collisional widths for the transitions with J values from 8 to 38. Our experimental line positions are in excellent agreement with those derived from molecular constants given on the literature. The observed line…

High-resolution non-linear Raman spectroscopy in gases

1990

The resolution in the Raman spectra of gases has been greatly improved by the development of the different methods of non-linear Raman scattering. When two laser beams, one of which has a tunable frequency, are focused in a sample, a stimulated Raman process occurs as soon as the frequency difference between the two lasers is equal to a Raman-active rovibrational or rotational transition frequency. The Raman resonance can be detected in different ways: by coherent anti-Stokes Raman scattering (CARS) or the corresponding Stokes process (CSRS), by a gain in one of the beams (stimulated Raman gain spectroscopy, SRGS) or a loss in the other (inverse Raman spectroscopy, IRS), or even by detectio…

Communication modes in vector diffraction

2010

The communication modes, which mathematically correspond to singular value decomposition, have proven a useful concept in optical scalar-field diffraction, with applications in resolution studies, image synthesis, and wave propagation. For optical near-field geometries the communication modes have to be extended to electromagnetic field accounting for the polarization properties. In this paper we present the vector-valued communication modes method based on the rigorous electric-field diffraction integral. As a special case the transverse-electric scalar field modes are obtained. The intensity and polarization properties of the leading electromagnetic communication modes in near-field arran…

CFD simulations of dense solid–liquid suspensions in baffled stirred tanks: Prediction of solid particle distribution

2013

Abstract Industrial tanks devoted to the mixing of solid particles into liquids are often operated at an impeller speed N less than Njs (defined as the lowest speed allowing the suspension of all particles): under such conditions the distribution of solid-particles is very far from being homogeneous and very significant concentration gradients exist. The present work is devoted to assessing the capability of Computational Fluid Dynamics (CFD) in predicting the particle distribution throughout the tank. The CFD model proposed by Tamburini et al. [58] and successfully applied to the prediction of the sediment amount and shape was adopted here to simulate the particle distribution under partia…