Search results for "VISCOSITY"
showing 10 items of 542 documents
Local Viscosity in the Vicinity of a Wall Coated by Polymer Brush from Green-Kubo Relations
2008
When fluids are confined in slit pores between parallel walls, their static structures and their dynamical properties exhibit inhomogeneity in the z-direction perpendicular to the wall. Of particular interest are local bulk viscosity η b (z) and shear viscosity η s (z). Here, we discuss an algorithm to estimate these quantities from Green-Kubo relations using equilibrium molecular dynamics. As an application example, a polymer brush (macromolecules end-grafted to a substrate at z= 0) interacting with a solvent formed from point-like particles is given.
Next-to-leading order improved perturbative QCD + saturation + hydrodynamics model for A + A collisions
2014
We calculate initial conditions for the hydrodynamical evolution in ultrarelativistic heavy-ion collisions at the LHC and RHIC in an improved next-to-leading order perturbative QCD + saturation framework. Using viscous relativistic hydrodynamics, we show that we obtain a good simultaneous description of the centrality dependence of charged particle multiplicities, transverse momentum spectra and elliptic flow at the LHC and at RHIC. In particular, we discuss how the temperature dependence of the shear viscosity is constrained by these data.
Collective dynamics in relativistic nuclear collisions
2014
Abstract I will review the current status of describing spacetime evolution of the relativistic nuclear collisions with fluid dynamics, and of determining the transport coefficients of strongly interacting matter. The fluid dynamical models suggest that shear viscosity to entropy density ratio of the matter is small. However, there are still considerable challenges in determining the transport coefficients, and especially their temperature dependence is still poorly constrained.
Flow analysis with 3-dim ultra-relativistic hydro
2009
We review how flow observables of ultra-relativistic heavy-ion collisions are influenced by the initial condition, the description of the fluid dynamical (FD) stage and freeze-out (FO). We discuss the effects of the resolution of the FD treatment, the arising smoothing and numerical viscosity, as well as the consequences of final FO. This final FO stage includes confinement and simultaneous formation of constituent quarks. From the energy and momentum conservation at the FO stage pressure change and flow velocity may occur, which further modifies the observables.
Haematocrit in metabolic syndrome
2004
In this paper are described normal and insulin resistant subjects, correlating the haematocrit value with M-index during euglycaemic hyperinsulinaemic clamp. The haematocrit value is related negatively with the M-value. We conclude that insulin resistance is a possible factor in determinating the blood viscosity in relation with the red cells/plasma ratio.
Dielectric behaviour of a γ-irradiated polycarbonate
1980
Dielectric measurements on a γ-irradiated polycarbonate in a dose range 0–20 Mrad and at test frequencies of 103 and 104 Hz have been carried out. The glass transition temperature shows a maximum at 3.5 Mrad and then decreases at larger doses. This result is in line with other experiments (intrinsic viscosity, dynamic-mechanical measurements, etc) already reported: the Tg values are however larger in the present results. This is probably due to the plasticizing action of the absorbed moisture present in the previous tests. A Tg vs 1/[n]2 plot (1/[n]2 is proportional to 1/m ) allows to find the value of the glass transition point at an infinite molecular weight and the dependency of Tg on mo…
Toward more realistic viscosity measurements of tyre rubber–bitumen blends
2014
AbstractThe measurement of rheological properties of the tyre rubber bitumen blends is often challenging due to presence of suspended tyre rubber’s crumbs. Furthermore, the phase separation during the course of measurements makes the viscosity of these non-homogeneous blends difficult to ascertain. In this study, a new dual helical impeller was designed and manufactured to be used with a rotational viscometer in order to have a real-time control of the viscosity while performing a laboratory mixing of the blends. Layer based manufacturing techniques showed to be a convenient method to produce complex shaped impeller prototypes before manufacturing the more expensive stainless steel assembly…
13C spin-lattice relaxation study of chlorinated alkanes
1987
The spin-lattice relaxation of ten polychloroalkanes (ethanes to pentanes) have been studied both neat and in a 50% solution in CDCl3. The T1 values for the CH2, CH2Cl and CHCl2 carbons decrease with increasing molecular weight in accordance with a dipolar-dominated mechanism, whereas those of the CCl3 carbons showed no dependence on molecular weight. In chloropentanes, with chlorine substitution at one end only, the frequency of segmental motion begins to compete with that of overall tumbling of the molecule. Consequently, the T1 minimum is shifted from the middle towards the heavier end of the molecule, and also a relatively large T1 for the terminal methyl is observed. It was also demons…
Dynamics of pistachio oils by proton nuclear magnetic resonance relaxtion dispersion
2011
A number of pistachio oils were selected in order to test the efficacy of nuclear magnetic resonance relaxation dispersion (NMRD) technique in the evaluation of differences among oils (1) obtained from seeds subjected to different thermal desiccation processes, (2) retrieved from seeds belonging to the same cultivar grown in different geographical areas and (3) produced by using seed cultivars sampled in the same geographical region. NMRD measures relaxation rate values which are related to the dynamics of the chemical components of complex food systems. Results not only allowed to relate kinematic viscosity to relaxometry parameters but also were successful in the differentiation among the…
Rheological and Flocculation Analysis of Microfibrillated Cellulose Suspension Using Optical Coherence Tomography
2018
A sub-micron resolution optical coherence tomography device was used together with a pipe rheometer to analyze the rheology and flocculation dynamics of a 0.5% microfibrillated cellulose (MFC) suspension. The bulk behavior of the MFC suspension showed typical shear thinning (power-law) behavior. This was reflected in a monotonously decreasing floc size when the shear stress exceeded the yield stress of the suspension. The quantitative viscous behavior of the MFC suspension changed abruptly at the wall shear stress of 10 Pa, which was reflected in a simultaneous abrupt drop of the floc size. The flocs were strongly elongated with low shear stresses. With the highest shear stresses, the flocs…