Search results for "Stokes"

Long time behavior for a dissipative shallow water model

2013

We consider the two-dimensional shallow water model derived by Levermore and Sammartino (Nonlinearity 14,2001), describing the motion of an incompressible fluid, confined in a shallow basin, with varying bottom topography. We construct the approximate inertial manifolds for the associated dynamical system and estimate its order. Finally, considering the whole domain R^2 and under suitable conditions on the time dependent forcing term, we prove the L^2 asymptotic decay of the weak solutions.

Infrared and Raman spectroscopy of WO3 and CdWO4

2001

Abstract Infrared reflection and Raman spectroscopy have been applied to study the vibrational modes of tungsten trioxide (WO 3 ) and cadmium tungstate (CdWO 4 ). Kramers–Kronig relations are employed to yield the refractive index as well as TO and LO functions of these materials at frequencies from 50 to 1200 cm −1 . The symmetry of the vibrations of CdWO 4 is reported.

Chydenius-Instituutti alueensa tuotantovoimana : instituutin vaikuttavuus sidosryhmien näkökulmasta

2000

Tutkimuksen tavoitteena on ymmärtää ja jäsentää Chydenius-Instituutin alueellista vaikuttavuutta paneutumalla ensisijaisesti instituutin keskeisten sidosryhmien puheisiin ja niiden kantamiin merkiryksiin. Huomion kohteina ovat instituutin vaikuttavuutta koskevat hallitsevat ja marginaaliset puhetavat. Toissijainen aineisto koostuu keskipohjalaisille kunnanvaltuutetuille osoitetusta kyselystä, jossa tiedusteltiin heidän käsityksiään Chydenius-Instituutin tunnettuudesta ja vaikuttavuudesta. Tutkimuksen käytännöllisenä tarkoituksena on oivaltaa ja sommitella Chydenius-Instituutista sellaisia todellisuuskuvia, joiden asetelmissa ja väreissä instituutti kykenee entisestään vahvistumaan, kehittym…

Zero Viscosity Limit for Analytic Solutions of the Navier-Stokes Equation on a Half-Space.¶ II. Construction of the Navier-Stokes Solution

1998

This is the second of two papers on the zero-viscosity limit for the incompressible Navier-Stokes equations in a half-space in either 2D or 3D. Under the assumption of analytic initial data, we construct solutions of Navier-Stokes for a short time which is independent of the viscosity. The Navier-Stokes solution is constructed through a composite asymptotic expansion involving the solutions of the Euler and Prandtl equations, which were constructed in the first paper, plus an error term. This shows that the Navier-Stokes solution goes to an Euler solution outside a boundary layer and to a solution of the Prandtl equations within the boundary layer. The error term is written as a sum of firs…

Weld pool surface temperature measurement from polarization state of thermal emission

2014

This paper presents a passive polarimetry method using a division of aperture optical device in order to measure the temperature distribution at the weld pool surface. Thermal emission from a hot liquid metal was investigated at a near-infrared wavelength corresponding to a blind spectral window of a helium plasma generated during gas tungsten arc welding process. The refractive index of liquid metal and the surface radiance are deduced from the polarisation state of thermal emissions. Based upon the knowledge of both characteristics, the temperature distribution can be calculated. Conseil Régional de Bourgogne

A DERIVATION OF THE VLASOV-NAVIER-STOKES MODEL FOR AEROSOL FLOWS FROM KINETIC THEORY

2016

This article proposes a derivation of the Vlasov-Navier-Stokes system for spray/aerosol flows. The distribution function of the dispersed phase is governed by a Vlasov-equation, while the velocity field of the propellant satisfies the Navier-Stokes equations for incompressible fluids. The dynamics of the dispersed phase and of the propellant are coupled through the drag force exerted by the propellant on the dispersed phase. We present a formal derivation of this model from a multiphase Boltzmann system for a binary gaseous mixture, involving the droplets/dust particles in the dispersed phase as one species, and the gas molecules as the other species. Under suitable assumptions on the colli…

High-Resolution Stimulated Raman Spectroscopy of Methane 13CD4 in the Pentad Region

1988

Abstract We present the first Raman spectrum of 13CD4 recorded at room temperature in the pentad region by inverse Raman spectroscopy, thus including the ν1 (A1), 2ν2 (A1), 2ν4 (A1), and ν2 + ν4(F1 + F2) Q branches. It is noteworthy that the overtone bands 2ν2 and 2ν4 are observed for the first time in a methane-like molecule by a coherent Raman process. The wide frequency range investigated, covering 45 cm−1 in three parts, contains more than 300 lines with uncertainty less than 10−3 cm−1 in most cases. These Raman data are combined with high-resolution infrared data in a weighted least-squares fit of the vibration-rotation constants of the pentad, thanks to a relevant partially reduced ef…

2020

Abstract. Quantifying the hydraulic properties of single fractures is a fundamental requirement to understand fluid flow in fractured reservoirs. For an ideal planar fracture, the effective flow is proportional to the cube of the fracture aperture. In contrast, real fractures are rarely planar, and correcting the cubic law in terms of fracture roughness has therefore been a subject of numerous studies in the past. Several empirical relationships between hydraulic and mechanical aperture have been proposed based on statistical variations of the aperture field. However, often, they exhibit non-unique solutions, attributed to the geometrical variety of naturally occurring fractures. In this st…

Transient absorption with a femtosecond tunable excitation pump reveals the emission kinetics of color centers in amorphous silica.

2021

We report a set of femtosecond (fs) transient absorption (TA) measurements following the dynamics of the so-called nonbridging oxygen hole center in silica, a model color center in wide bandgap amorphous solids, characterized by a very large Stokes shift between the UV excitation and its associated red emission at 1.9 eV. The changes in the TA spectrum were probed in the UV-visible range at various delays after photoexcitation and analyzed as a function of the UV excitation energy, in single-photon absorption conditions. The combination of the experiments helps to clarify the defect photocycle, highlighting how TA measurements with tunable UV excitation could represent a powerful tool to in…

The methane Raman spectrum from 1200 to 5500 cm(-1): A first step toward temperature diagnostic using methane as a probe molecule in combustion syste…

2005

International audience; We present a study of the spontaneous Raman spectra of (CH4)-C-12 from 1200 to 5500 cm(-1) at various temperatures. This study is of interest from a fundamental as well as from a practical point of view with regards to the temperature diagnostic in hydrocarbon combustion. The present investigation shows that the spontaneous (CH4)-C-12 Raman spectra are very sensitive to temperature and that the complexity of methane spectra is not an obstacle to use methane as a probe molecule in laser-diagnostic techniques. Our study consists in determining the polarisability parameters of methane (CH4)-C-12, unknown at the present time, from spontaneous Raman spectra recorded at pr…