28 research outputs found
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Molecular dynamics simulation of plane poiseuille flow in nanochannels
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.This paper presents new techniques and results of simulating microflows in plane channels by the molecular dynamics (MD) method. Mass forces and thermostat are not used in these techniques. The flows are simulated by both hard-sphere molecules and molecules with the Lennard-Jones intermolecular potential. Flow at a given fluid flow rate is implemented. In this case, the initial shock profile is transformed to a parabolic type profile. However, unlike in ordinary Poiseuille flows, a slip effect is recorded on the channel walls. It is shown that, in a nanochannel, a linear pressure gradient occurs. Fluid structuring is studied. The effects of fluid density, accommodation coefficients, and channel dimensions on flow properties are investigated.This work was supported in part by the Russian Foundation for Basic Researches (grant No. 07-08-00164) and by the grant of
the President of the Russian Federation for
Support of Leading Scientific Schools (project no. NSh-454.2008.1)
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Micromixers simulation
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.A method for simulating fluid flows in microchannels is proposed. The method is tested using available experimental data obtained in micro-PIV studies of microchannel flows. Flow regimes in Y- and Ttype micromixers are studied. Passive and active mixers are considered. The dependence of the mixing efficiency on the Peclet number is examined, and the possibility of using hydrophobic and ultrahydrophobic
coatings is analyzed. An active mixing method using a T-mixer with a harmonically varying flow rate at one of the inlet channels is studied. The dependence of the mixing efficiency on the frequency and amplitude of flow rate variation is determined.This work was supported in part by the Russian Foundation for Basic Researches (grant No. 07-08-00164) and by the grant of the President of the Russian Federation for Support of Leading Scientific Schools (project no. NSh-454.2008.1)
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Viscosity and thermal conductivity of nanofluids
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.The purpose of the present work was to study the momentum and energy transport processes in nanofluids by the molecular dynamics (MD) method. The MD-simulation results were compared with known formulae and experimental data. Unlike for suspensions with Brownian and other macroscopic particles, the viscosity and thermal conductivity of nanofluids were found to depend not only on the volume fraction of
nanoparticles but also on the mass and radius of nanoparticles. The possible mechanisms of the nanoparticle effect on the transport coefficients of nanofluids are discussed.This work was supported in part by the RFBR grant No. 07-08-00164)
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Self-diffusion and viscosity coefficient of fluids in nanochannels
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Fluid viscosity and molecular diffusion in nanochannels were studied by molecular dynamics simulation. Transport processes in a plane channel, a channel of rectangular cross-section, and in porous media were investigated. The channel height was varied from 2 to 50 nm. The interaction between molecules was simulated using the hard sphere (HS) and the Lennard-Jones (LJ) intermolecular potentials. The porous matrix was modeled by cubic packing of spheres of the same radius, and the packing density and the grain size were varied. The dependence of the transport coefficients on the fluid density and channel characteristics (channel height, channel aspect ratio, porosity of the porous medium, accommodation coefficients, etc.) was investigated.Russian Foundation for Basic Research (Grant
No. 10-01-00074) and the Federal Special
Program “Scientific and scientific-pedagogical personnel of innovative Russia in 2009-2013” (projects No. P230 and No. 14.740.11.0579, No. 14.740.11.0103)
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Mixing in a T-type micromixer at high Reynolds numbers
This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Flow regimes and mixing performance in a T-type micromixer at high Reynolds numbers were
studied by numerical solution of the Navier–Stokes equations. The Reynolds number was varied from one to one thousand. The cross section of the mixing channel was 100 μm×200 μm, and its length was 1400 μm. The transverse inlet channels were symmetric about the mixing channel, and their cross-section was 100 μm×100 μm, and the total length was 800 μm. Five different flow regimes were identified: (i) stationary vortex-free flow (Re 400). Maximum mixing efficiency was obtained for stationary asymmetric vortex flow. In this case, an S-shaped vortex structure formed in the flow field. The effect of the slip conditions on the flow pattern and mixing efficiency are studied.The Russian Foundation for Basic Research (Grant No. 10-01-00074) and the Federal Special Program “Scientific and scientific-pedagogical personnel of innovative Russia in 2009-2013” (projects No. P230, No. 14.740.11.0579 and No. 14.740.11.0103)
Characterization techniques for studying the properties of nanocarriers for systemic delivery
Nanocarriers have attracted a huge interest in the last decade as efficient drug delivery systems and diagnostic tools. They enable effective, targeted, controlled delivery of therapeutic molecules while lowering the side effects caused during the treatment. The physicochemical properties of nanoparticles determine their in vivo pharmacokinetics, biodistribution and tolerability. The most analyzed among these physicochemical properties are shape, size, surface charge and porosity and several techniques have been used to characterize these specific properties. These different techniques assess the particles under varying conditions, such as physical state, solvents etc. and as such probe, in addition to the particles themselves, artifacts due to sample preparation or environment during measurement. Here, we discuss the different methods to precisely evaluate these properties, including their advantages or disadvantages. In several cases, there are physical properties that can be evaluated by more than one technique. Different strengths and limitations of each technique complicate the choice of the most suitable method, while often a combinatorial characterization approach is needed