The results of research on the effect of the presence of viscosity on evolution of perturbations in the system of colliding plates are presented in this work. The range of amplitudes of the initial ...perturbations wavelengths, at which the effect of viscosity may be neglected, are determined. Comparison of analytical and numerical results are shown.
•CFD-PBM model was developed to simulate bubble column with viscous liquids.•Two mass transfer models were used to calculate mass transfer coefficient kl.•Slip penetration model gave better ...predictions of kla than eddy cell model.•Effect of liquid viscosity was well predicted by CFD-PBM model in a wide range.
It is important to understand the gas–liquid mass-transfer performance for the reactor design and scale-up of bubble columns. Air-water bubble columns have been extensively simulated, however the simulation of bubble columns with often used high-viscosity liquids are limited. Here, the CFD-PBM coupled model was developed to simulate the mass transport characteristics in a bubble column with liquid viscosity from 1.0 to 39.6 mPa·s and superficial gas velocity from 0.02 to 0.3 m/s. The gas-liquid interfacial area a was estimated from the simulated local gas holdup and bubble size distribution. Two typical theoretical mass transport models were used to calculate the liquid-side mass transfer coefficient kl. The volumetric mass transfer coefficient kla, calculated from a and kl, significantly decreased with increasing liquid viscosity. Overall, the coupled model accurately predicted the effect of liquid viscosity on mass transport in a wide liquid viscosity.
The viscosity of the slag constituted by 55%CaF2–20%CaO–3%MgO–22%Al2O3–x%B2O3 (mass fraction: x ≤ 3) was measured by rotating cylinder method during the electroslag remelting (ESR) of 9CrMoCoB steel ...to analyze the effects of the B2O3 content on slag viscosity, break point temperature, and activation energy for viscous flow. Meanwhile, the slag’s structural characteristics were studied by Raman spectrometry. Results indicated that when T ≥ 1663 K, the viscosity changed gently with temperature, showing the value of about 0.055 Pa·s, which was rarely affected by w(B2O3). However, with the increase of w(B2O3) in the slag, the Ca3B2O6 with a low melting point was formed, reducing the slag’s break point temperature from 1628 K to 1563 K. According to the NBO/T value and Raman spectra, B2O3, as a network generating oxide, improved the slag’s degree of polymerization, thus strengthening and complicating its network structure at high temperatures. In addition, as the w(B2O3) increased from 0 to 3%, the activation energy for viscous flow rose from 64 kJ·mol−1 to 94 kJ·mol−1 in the slag.
The expressions of the shear viscosity and the bulk viscosity components in the presence of an arbitrary external magnetic field for a system of hot charged scalar bosons (spin 0) as well as for a ...system of hot charged Dirac fermions (spin 1/2) have been derived by employing the one-loop Kubo formalism. This is done by explicitly evaluating the thermomagnetic spectral functions of the energy-momentum tensors using the real time formalism of finite temperature field theory and the Schwinger proper time formalism. In the present work, a rich quantum field theoretical structure in the expressions of the viscous coefficients in nonzero magnetic field are found, which are different from their respective expressions obtained earlier via kinetic-theory-based calculations; though, in the absence of a magnetic field, the one-loop Kubo and the kinetic-theory-based expressions for the viscosities are known to be identical. We have identified that Kubo and kinetic-theory-based results of viscosity components follow a similar kind of temperature and magnetic field dependency. The relaxation time and the synchrotron frequency in the kinetic theory formalism are realized to be connected, respectively, with the thermal width of propagator and the transitions among the Landau levels of the charged particles in the Kubo formalism. We believe that the connection of the latter quantities is quite new and probably the present work is the first time addressing this interpretation along with the new expressions of viscosity components, not seen in existing works.
Serial crystallography of membrane proteins often employs high‐viscosity injectors (HVIs) to deliver micrometre‐sized crystals to the X‐ray beam. Typically, the carrier medium is a lipidic cubic ...phase (LCP) media, which can also be used to nucleate and grow the crystals. However, despite the fact that the LCP is widely used with HVIs, the potential impact of the injection process on the LCP structure has not been reported and hence is not yet well understood. The self‐assembled structure of the LCP can be affected by pressure, dehydration and temperature changes, all of which occur during continuous flow injection. These changes to the LCP structure may in turn impact the results of X‐ray diffraction measurements from membrane protein crystals. To investigate the influence of HVIs on the structure of the LCP we conducted a study of the phase changes in monoolein/water and monoolein/buffer mixtures during continuous flow injection, at both atmospheric pressure and under vacuum. The reservoir pressure in the HVI was tracked to determine if there is any correlation with the phase behaviour of the LCP. The results indicated that, even though the reservoir pressure underwent (at times) significant variation, this did not appear to correlate with observed phase changes in the sample stream or correspond to shifts in the LCP lattice parameter. During vacuum injection, there was a three‐way coexistence of the gyroid cubic phase, diamond cubic phase and lamellar phase. During injection at atmospheric pressure, the coexistence of a cubic phase and lamellar phase in the monoolein/water mixtures was also observed. The degree to which the lamellar phase is formed was found to be strongly dependent on the co‐flowing gas conditions used to stabilize the LCP stream. A combination of laboratory‐based optical polarization microscopy and simulation studies was used to investigate these observations.
This is a study of the phase changes detected in monoolein samples under constant flow using a high‐viscousity injector. The sample behaviour was studied using X‐ray techniques while light microscopy and modelling studies were used to help interpret some of the effects observed in the data.
The ratio of the dispersed phase viscosity to that of the continuous phase is a critical parameter for microfluidic two‐phase flows. Here, the influence of the viscosity ratio on liquid‐liquid flow ...in T‐shaped microchannels is studied experimentally. Three basic flow patterns, i.e., parallel, plug, and droplet flow, are observed for different sets of immiscible liquids. Flow pattern maps are plotted and generalized using a combination of Weber and Ohnesorge dimensionless numbers. In the plug flow pattern, interface deformations occur for low viscosity ratios. Existing correlations from the literature are tested against experimental data for plug velocity and lengths. Despite the significant plug interface deformations, the influence of the viscosity ratio on the plug length and velocity is negligible.
The influence of the viscosity ratio, λ = μd/μc, on the flow patterns in liquid‐liquid microfluidic flows in T‐shaped microchannels was investigated experimentally. Flow pattern maps are plotted and generalized using the Weber and Ohnesorge dimensionless numbers. Despite the significant plug interface deformations, the influence of the viscosity ratio on the plug length and velocity is negligible.
This study examines the volumetric, viscometric and UV–vis characteristics of L-Citrulline in water and aqueous saccharides at atmospheric pressure across the whole concentration range and the ...absorber operating temperature range of 293.15 K -313.15 K. Density, partial molar volume, apparent molar isobaric expansion, Hepler's constant and hydration number were among the examined volumetric parameters, and viscosity coefficients, viscosity deviation and free energy for viscous flow activation were among the examined viscometric parameters. Stronger interactions between L-Citrulline and L-Arabinose were indicated by the increase in the transfer characteristics in the following order: L-Arabinose > D-xylose. A comparison of the taste behaviours of L-Citrulline in water and in an aqueous solution of saccharides has also been attempted. L-Citrulline interacts with all solvents in a significant way, as evidenced by the UV–visible spectra suggested by the shift in UV–visible absorption maxima that correspond with a rise in L-Citrulline content in the solvent systems chosen.
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•Solvation behaviour of L-Citrulline was examined via volumetric, viscometric and UV–vis study.•L-Arabinose interacted strongly with L-citrulline as compared to D-xylose.•L-Citrulline is likely to have a tendency to break structural bonds in aqueous solutions.•Over hydrophobic–hydrophobic interactions, ion-hydrophilic interactions predominate.
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Nanofluids as heat transfer fluids have shown huge potential in heat exchange systems. How to balance effective thermal conductivity, dispersion stability and viscosity has become one ...of crucial issues for the application of nanofluids. MXene nanosheets with high aspect ratio coupled with high thermal conductivity and hydrophilic properties are expected to be potential fluids fillers. In this study, comprehensive performance of ethylene glycol (EG) based nanofluids containing multilayer and delaminated single layer Ti3C2Tx MXene are investigated in detail. The thermal conductivity of nanofluids with 5 vol% of multilayer and single layer Ti3C2Tx increase by 53.1% and 64.9% compared with EG, respectively. It is interesting that the viscosity of 1 vol% of MXene nanofluids is much lower than those of graphene and multi-walled carbon nanotube with 0.1 vol% due to the excellent self-lubricating properties. Single layer Ti3C2Tx-EG nanofluids also exhibit excellent stability and no obvious sedimentation in 30 days. The detailed study on MXene nanofluids will provide a strategy for heat transfer fluids development.
Viscosity versus shear rate curves have been measured up to 10
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for a range of VM solutions and fully formulated oils of known composition at several temperatures. This shows large differences ...in the shear thinning tendencies of different engine oil VMs. It has been found that viscosity versus shear rate data at different temperatures can be collapsed onto a single master curve using time–temperature superposition based on a shear rate shift factor. This enables shear thinning equations to be derived that are able to predict the viscosity of a given oil at any shear rate and temperature within the range originally tested. One of the tested lubricants does not show this time temperature superposition collapse. This fluid also exhibits extremely high viscosity index and shear thins more easily at high than at low temperature, unlike all the other solutions tested. This unusual response may originate from the presence on the VM molecules of two structurally and chemically different components. In a companion paper, the master shear thinning curves obtained in this paper are used to explore how VMs impact film thickness and friction in a steadily loaded, isothermal journal bearing
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