Viscosity Of Silicone Oil Research Articles

Experimental characterization of three-dimensional corner flows at low Reynolds numbers

AbstractWe investigate experimentally the characteristics of the flow field that develops at low Reynolds numbers ($\mathit{Re}\ll 1$) around a sharp $9{0}^{\ensuremath{\circ} } $ corner bounded by channel walls. Two-dimensional planar velocity fields are obtained using particle image velocimetry (PIV) conducted in a towing tank filled with a silicone oil of high viscosity. We find that, in the vicinity of the corner, the steady-state flow patterns bear the signature of a three-dimensional secondary flow, characterized by counter-rotating pairs of streamwise vortical structures and identified by the presence of non-vanishing transverse velocities (${u}_{z} $). These results are compared to numerical solutions of the incompressible flow as well as to predictions obtained, for a similar geometry, from an asymptotic expansion solution (Guglielmini et al., J. Fluid Mech., vol. 668, 2011, pp. 33–57). Furthermore, we discuss the influence of both Reynolds number and aspect ratio of the channel cross-section on the resulting secondary flows. This work represents, to the best of our knowledge, the first experimental characterization of the three-dimensional flow features arising in a pressure-driven flow near a corner at low Reynolds number.

Characteristics of the breakup and fragmentation of an electrohydrodynamic melt jet

In this study, the breakup of a melt jet into a viscous medium is investigated in the presence of an intense electric field. Fragmentation of the melt jet occurs due to both hydrodynamic and electrohydrodynamic (EHD) forces within two kinds of silicone oil of different viscosities. The size and shape characteristics of the produced particles have been studied using SEM images, and the particle size distributions were found to exhibit considerable variations when a voltage was applied and when both the viscosity and temperature of the base fluid were changed. The morphologies of the particles were also affected by the same parameters. For instance, by applying EHD force, significant enhancements in size reduction and increased roundness of the particles occurred. The breakup process of the melt jet was found to be dominant by hydrodynamic or electrohydrodynamic instabilities, depending on the situation. Governing mechanisms (instability) in the cases of pure hydrodynamic and electrohydrodynamic fragmentations are discussed.

SYNTHESIS OF TITANATE/POLYPYRROLE COMPOSITE ROD-LIKE PARTICLES AND THE ROLE OF CONDUCTING POLYMER ON ELECTRORHEOLOGICAL EFFICIENCY

In this paper, we study the preparation of titanate/polypyrrole core-shell rod-like composite particles. The mere titanate rod-like particles were prepared as core material and PPy was polymerized on their surface in different amounts. Rheological measurements showed that under an applied external electric field, shear stress of these materials significantly increased with amount of PPy in the shell layer. The yield stresses obtained from the Cho-Choi-Jhon model were correlated with dielectric properties of suspensions. Polarizability as a measure of particle polarization obtained from Havriliak–Negami model of dielectric spectra increases with the content of PPy in the samples. Furthermore, role of particle concentration and silicone oil viscosity was also investigated.

Experimental investigation of the effect of liquid viscosity on slug flow in small diameter bubble column

The effect of liquid viscosity on slug flow in a 50 mm diameter bubble column was investigated experimentally using air-silicone oil as operating fluid with silicone oil of viscosities 5, 100, 1000 and 5000 mPa.s. Data was collected using Electrical Capacitance Tomography (ECT), a non-intrusive advanced instrumentation measuring technique and the high Speed Video Camera, through which the slug parameters such as length of Taylor bubbles and liquid slug, void fraction in Taylor bubbles and liquid slug, slug frequency, film thickness and pressure gradient in the slug, were measured and analyzed. The analysis was done using the void fraction time series, probability density function and power spectral density plots. Superficial gas velocities of 0.02≤Ugs ≤0.361 m/s were used in the experiment. It was also observed that as viscosity increases, slug frequency, structure velocity, length of liquid slug, void fraction in liquid slug and void fraction in Taylor bubbles decreases; while the length of Taylor bubble, film thickness and pressure gradient in the slug increases.

The 7-channel FIR HCN interferometer on J-TEXT tokamak

A seven-channel far-infrared hydrogen cyanide (HCN) laser interferometer has been established aiming to provide the line integrated plasma density for the J-TEXT experimental scenarios. A continuous wave glow discharge HCN laser designed with a cavity length 3.4 m is used as the laser source with a wavelength of 337 μm and an output power up to 100 mW. The system is configured as a Mach-Zehnder type interferometer. Phase modulation is achieved by a rotating grating, with a modulation frequency of 10 kHz which corresponds to the temporal resolution of 0.1 ms. The beat signal is detected by TGS detector. The phase shift induced by the plasma is derived by the comparator with a phase sensitivity of 0.06 fringe. The experimental results measured by the J-TEXT interferometer are presented in details. In addition, the inversed electron density profile done by a conventional approach is also given. The kinematic viscosity of dimethyl silicone and vibration control is key issues for the system performance. The laser power stability under different kinematic viscosity of silicone oil is presented. A visible improvement of measured result on vibration reduction is shown in the paper.

0205 高粘度MR流体のマグネトレオロジー効果(OS2 機能性流体とその先進応用,オーガナイズドセッション)

Magnetorheological (MR) fluids have many attractive features, including high yield strength, low viscosity and stable hysteretic behavior over a broad temperature range. In general, low viscosity MR fluids are widely acceptable to the applications to industrial devices with low energy loss under no magnetic field. While, although high viscosity MR fluids are suitable for some applications such as torque converters, viscous couplings, and damping devices which need fail-safe, there is almost no research to investigate the properties of high viscous MR fluids. In this research, the rheological properties and particle settling rate of high viscous MR fluids have been investigated, focusing on the effects of the MR fluid viscosity on its induced yield stress, flow curves and particle settling rate. The tested MR fluids are suspensions of micron-sized carbonyl iron particles dispersed into high viscosity silicone oils and mineral oil. The rheological properties in constant rpm tests and oscillatory tests have been measured using a HAAKE RSI50 parallel disk rheometer with magnetic circuit. An effective means of producing a stable MR fluid is by the increase of viscosity and the addition of anti-settling agent.

Lubrication of Microelectromechanical Devices Using Liquids of Different Viscosities

Lubrication of contacting and sliding surfaces in MEMS (microelectromechanical systems) is particularly challenging because of the predominance of surface forces at the microscale. The current paper explores the possibility of using liquid lubrication in this application. Measurements of friction and lubricant film thickness have been made for liquid lubricants of different viscosities, including low viscosity silicone oil, hexadecane, squalane, and water. Testing was carried out using a newly developed MEMS tribometer in which a rotating silicon disk is loaded against a stationary silicon disk. Two different test setups were used: one where both disks are flat, and the other where the stationary disk is structured as in a thrust pad bearing. In all tests the disks were fully submerged in the lubricant. With the flat-on-patterned disk combination, the variation of friction with rotation speed was found to follow classical Stribeck curves for all the lubricants tested. The friction at high speeds also decreased with increasing normal load, in accordance with hydrodynamic lubrication theory. For the least viscous lubricants, it was found that the hydrodynamic friction coefficients remained relatively low even at higher speeds. In particular, for water the friction coefficient for water was around 0.1 at 10,000 rpm. However, boundary friction was found to be unacceptably high at low speeds where there was insufficient lubricant entrainment. The experimental results have been compared with a finite difference solution of Reynolds equation and reasonable agreement is seen between theory and experiment. The results indicate that liquid lubrication is potentially an effective means of lubricating MEMS components with high levels of sliding.

Electrorheological properties of suspensions of hollow globular titanium oxide/polypyrrole particles

Hollow globular clusters of titanium oxide (TiO2) nanoparticles were synthesized by a simple hydrothermal method. The prepared particles were consequently coated by in situ polymerization of conductive polymer polypyrrole (PPy) to obtain novel core–shell structured particles as a dispersed phase in electrorheological (ER) suspensions. The X-ray diffraction analysis and scanning electron microscopy provided information on particle composition and morphology. It appeared that PPy coating improved the compatibility of dispersed particles with silicone oil which results in higher sedimentation stability compared to that of mere TiO2 particles-based ER suspension. The ER properties were investigated under both steady and oscillatory shears. It was found that TiO2/PPy particles-based suspension showed higher ER activity than that of mere TiO2 hollow globular clusters. These observations were elucidated well in view of their dielectric spectra analysis; a larger dielectric loss enhancement and faster interfacial polarization were responsible for a higher ER activity of core–shell structured TiO2/PPy-based suspensions. Investigation of changes in ER properties of prepared suspensions as a function of particles concentration, viscosity of silicone oil used as a suspension medium, and electric field strength applied was also performed.

Selective control method for multiple magnetic helical microrobots

Microrobots have been investigated in recent years with the objective of discovering applications in the biomedical industry. The selective control of multiple microrobots is a challenging task; however, such control would allow for the dexterous manipulation of microscale objects. In this paper, we present a novel control method for the selective actuation of microrobots using only an external magnetic field. Such selective actuation of microrobots can be achieved by combining two types of external magnetic field rotations and two microrobotic designs, one with a bar-shaped head and the other with a cross-shaped head. After the type of rotation is chosen, the bar-shaped or the cross-shaped head can be individually actuated or both of them can be actuated simultaneously. To demonstrate the feasibility of the proposed method, millimeter-sized prototypes were fabricated and their individual actuation was successfully demonstrated in silicone oil. The prototypes showed the ability to swim in silicone oil (viscosity: 100 cSt) with a synchronized frequency of up to 0.25 Hz. This result suggests that the proposed method can be used in water at high input frequencies while taking the scaling effect into consideration. Hence, this method is expected to have many practical applications.

Behavior explanation and a new model for nonlinear viscous fluid dampers with a simple annular orifice

Viscous fluid dampers have been used in many building and bridge construction projects for earthquake damage mitigation. Previous study has shown that silicone oil properties, such as the fluid shear-thinning and relaxation effects, play important roles for the annular-orificed fluid damper behavior, and the Navier-Stokes equations based on these mechanisms were developed. In the current study, attempts are made to explain the effects of frequency, damper dimensions, and viscosity of silicone oil on the damper stiffness behavior using the developed equations. It is found that the developed equations successfully explain the observed phenomena. To avoid the complicated fluid dynamics analyses for damper parameters, such as the damping factor and the velocity power exponent, a new four-parameter equation considering both the fluid shear-thinning and stiffness effects, with a form similar to the widely used two- or three-parameter equation is proposed. The results of the new model successfully capture the damper behavior both at low and high frequencies and show an advantage that better consistent results can be obtained in the velocity range for the building and bridge applications.

Effect of the Viscosity of Silicone Oil on the Aggregation Behavior of C:F Clusters on a Silicone Oil Liquid Substrate

We investigate the effect of silicone oil viscosity on the aggregation behavior of C:F clusters deposited on silicone oil liquid substrates with viscous coefficients of 100, 350 and 500mm2/s by C4F8 dual-frequency capacitively coupled plasma. The aggregated C:F clusters all exhibit a branch-like fractal structure. However, the fractal dimension decreases from 1.67 to 1.45 with the silicone oil viscous coefficient increasing from 100mm2/s to 500 mm2/s. Owing to the fractal dimension of 1.67 and 1.45, corresponding to the diffusion-limited-aggregation (DLA) model and the cluster-cluster-aggregation (CCA) model respectively, the results show that the increase of silicone oil viscosity can lead to the change of C:F clusters aggregating on a silicone oil liquid substrate from DLA to CCA growth.

Rheological Behaviors of Nanofluids Containing Multi-Walled Carbon Nanotube

Stable nanofluids containing multi-walled carbon nanotubes (MWNTs) treated by concentrated acid and mechanical mill technology have been prepared. Water, ethylene glycol, glycerol, and silicone oil were used as base fluids. The rheological behaviors of the obtained nanofluids with different MWNT volume fractions and at different temperatures were investigated in details. The glycerol based and silicone oil based fluids behave Newtonian manner in all studied MWNT volume fractions and temperatures. The dispersant hexamethyldisiloxane added in silicone oil decreases the silicone oil viscosity but has no effect on the rheological properties of nanofluids. For the water based nanofluids, MWNTs act as lubricative function when the MWNT volume fraction is lower. Furthermore, for the ethylene glycol based and glycerol based fluid, almost no viscosity augmentation appears when the temperature is higher than 55°C.

Liquid lens using acoustic radiation force

A liquid lens is proposed that uses acoustic radiation force with no mechanical moving parts. It consists of a cylindrical acrylic cell filled with two immiscible liquids (degassed water and silicone oil) and a concave ultrasound transducer. The focal point of the transducer is located on the oil-water interface, which functions as a lens. The acoustic radiation force is generated when there is a difference in the acoustic energy densities of different media. An acoustic standing wave was generated in the axial direction of the lens and the variation of the shape of the oil-water interface was observed by optical coherence tomography (OCT). The lens profile can be rapidly changed by varying the acoustic radiation force from the transducer. The kinematic viscosity of silicone oil was optimized to minimize the response times of the lens. Response times of 40 and 80 ms when switching ultrasonic radiation on and off were obtained with a kinematic viscosity of 200 cSt. The path of a laser beam transmitted through the lens was calculated by ray-tracing simulations based on the experimental results obtained by OCT. The transmitted laser beam could be focused by applying an input voltage. The liquid lens could be operated as a variable-focus lens by varying the input voltage.

The viscosity of dimethyl silicone oil and the concentration of absorbed air

AbstractWe studied the viscosity behavior of 500 cSt dimethyl silicone oil with considerable concentration of absorbed air. For this purpose, a Couette rheometer with a transparent rotating outer cylinder and a fixed inner cylinder was established, in which the ambient pressure is controlled by a piston–cylinder apparatus. Careful torque calibration and equilibrium examination for the air–silicone–oil mixture were carried out. In the range of ambient pressure from 1 to 5 atm, corresponding to the air molar fraction from 11 to 35%, it was found that viscosity of the silicone oil decreases monotonically as the air concentration increases. The viscosity variation can be explained by the Eyring's model in which the free energy of activation is modified to account for the nonideality of the air–silicone–oil mixture. The excess free energy used to fit the viscosity variation is approximately equal to that used in the Krichevsky–Ilinskaya equation, which accounts for the nonideal solubility of the air–silicone–oil solution. The activation energy in the Arrhenius equation for viscosity–temperature relationship is identified as the activation enthalpy. © 2011 American Institute of Chemical Engineers AIChE J, 2011

Influence of intravitreous silicone oil on refractive state of eye and its relevant factors

目的 评估有晶状体或无晶状体囊膜是否保留的不同状态下硅油填充对眼屈光状态的影响,进一步探讨可能影响硅油填充眼屈光度改变的相关因素.方法 将行玻璃体硅油填充并拟行硅油取出的69眼依据晶状体的情况分为有晶状体眼组(n=34)、无晶状体囊膜保留完整组(n=22)和无晶状体无囊膜组(n=13).硅油取出前后行屈光度、视力、眼压、B型超声和超声生物显微镜(UBM)检查.采用多元回归法分析硅油取出前后术眼的屈光度差值与患者年龄、性别、眼别、术前屈光度、硅油填充时间和眼压的相关性.结果 有晶状体组、无晶状体囊膜(前或后)保留完整组及无晶状体无囊膜组硅油取出后屈光度的改变量分别为(-9.23±2.82)、(+1.09±2.50)、(+5.47±2.97)D,3组间屈光差值的差异有统计学意义(F=160.89,P=0.000).在有晶状体组中,硅油取出术后屈光度的改变量与年龄(r=-0.140,P=1.000)、性别(r=-0.164,P=0.982)、眼别(r=-0.008,P=0.981)、硅油填充时间(r=-289,P=0.997)和眼压(r=-0.038,P=1.000)间均无明显相关,但与硅油填充前屈光度呈负相关(r=-0.558,P=0.000).B型超声检查显示,坐位时硅油泡完全与后极部视网膜贴伏.UBM检查显示,在有晶状体眼及无晶状体眼中囊膜后均有玻璃体残留.结论 在晶状体、囊膜的不同状态下硅油取出术后的屈光度改变量各不相同.在有晶状体眼中,屈光度改变与硅油填充前术眼的屈光度有关.囊膜后玻璃体残留、囊膜的自身状态影响了硅油泡前表面的形态,导致个体差异性的产生。

Injectability of silicone oil-based tamponade agents

Background/aimsHigh viscosity silicone oils are used as tamponade agents to increase the resistance to emulsification; however, this makes the oils more difficult to inject. Increasing the extensional viscosity is one...

Friction Modifier Behaviour in Lubricated MEMS Devices

Low viscosity fluids could provide reliable lubrication for certain microelectromechanical system’s (MEMS) applications where high-sliding speeds and/or high sliding distances occur. However, while the use of low viscosity fluids leads to reduced hydrodynamic friction, high boundary friction can be a significant issue at low entrainment speeds. This article describes a series of tests of low viscosity fluids, blended with a friction modifier additive so as to provide a combination of both low hydrodynamic and low boundary friction at MEMS scales. The low viscosity fluids tested were hexadecane, low viscosity silicone oil, toluene and water. With the exception of water, the addition of the organic friction modifier octadecylamine to all these lubricating fluids produced a significant reduction in boundary friction. For a MEMS contact lubricated with silicone oil for instance, boundary friction was reduced from 0.5 to close to 0.05. The presence of the amine dissolved in the toluene had the effect of reducing boundary friction from 0.75 to 0.55; this was further reduced to 0.25 after the specimens had been immersed in the toluene-additive blend for 48 h. A water-soluble additive, diethylamine, was added to de-ionized water, at 0.1% by weight concentration. Although an initial reduction in boundary friction was observed (0.45–0.25), under these conditions the rapid onset of severe wear negated these effects. It is suggested that corrosion of silicon by water, followed by abrasion, is the cause of this accelerated wear.

A Study on the Spiral Polishing of the Inner Wall of Stainless Bores

This study investigates a spiral polishing mechanism in polishing the inner wall of stainless bore with the mixture grinding material of silicon carbide and polystyrene. The delicate polishing process is verified to be more efficient, cost-saving, and environment friendly than traditional processes. Varied sets of polishing parameters, including SiC grain size, SiC weight, polystyrene(PS) weight, viscosity of silicon oil, revolution speed of the driving screw, and machining time, are examined through the Taguchi Methods for optimum polishing effects. Impacts of different combinations of the six polishing parameters on surface roughness and texture are probed into and analyzed in the process of the experiment. The findings suggest that with the increase of time, the fluidity and stickiness of the abrasive medium improve, resulting in a finer polished surface within delicate spiral polishing process. It appears that significant differences are observed through the use of a mixture of 60 grams of SiC (with size of 7 μm) and 70 grams of polystyrene, silicon oil of 1000 mm2/s viscosity under the speed of 3500 rpm screw revolution speed for 30-minute machining time, improving the surface roughness from 0.90 μm to 0.158 μm Ra. The finding thus lends support to the effect of spiral polishing mechanism, which can be further developed.

Oxygen-selective immobilized liquid membranes for operation of lithium-air batteries in ambient air

In this work, nonaqueous electrolyte-based Li-air batteries with an O 2-selective membrane have been developed for operation in ambient air of 20–30% relative humidity (RH). The O 2 gas is continuously supplied through a membrane barrier layer at the interface of the cathode and ambient air. The membrane allows O 2 to permeate through while blocking moisture. Such membranes can be prepared by loading O 2-selective silicone oils into porous supports such as porous metal sheets and Teflon (PTFE) films. It was found that the silicone oil of high viscosity shows better performance. The immobilized silicone oil membrane in the porous PTFE film enabled the Li-air batteries with carbon black air electrodes to operate in ambient air (at 20% RH) for 16.3 days with a specific capacity of 789 mAh g −1 carbon and a specific energy of 2182 Wh kg −1 carbon. Its performance is much better than a reference battery assembled with a commercial, porous PTFE diffusion membranes as the moisture barrier layer on the cathode, which only had a discharge time of 5.5 days corresponding to a specific capacity of 267 mAh g −1 carbon and a specific energy of 704 Wh kg −1 carbon. The Li-air battery with the present selective membrane barrier layer even showed better performance in ambient air operation (20% RH) than the reference battery tested in the dry air box (<1% RH).

Investigation of the Mixing‐ and Devolatilization Behavior in a Continuous Twin‐Shaft Kneader

AbstractSummary: The technical synthesis and processing of polymer materials is the basis for major branches of the chemical industry. Well introduced for high‐viscosity processes are screw extruders. However, in case of large residence times a large volume kneader is more appropriate, but the latter still requires further understanding for intensification purposes. To achieve this, silicone oil of high viscosity is used as kneading material. First, the axial mixing behavior is characterized by studying the residence time distribution. The response functions show that the classical dispersion model leads to an appropriate description of the experimental data. By means of a fast chemical reaction of second order the radial mixing behavior including transport on the molecular scale is studied. The amount of detected product is a measure for the contact‐area produced by kneading and therefore for the mixing efficiency. Furthermore, the mass transfer from the silicone oil phase to the gas phase is investigated in two cases. Firstly, the transfer component is dissolved in the liquid phase and, secondly, it is dispersed in it. Both industry relevant cases are experimentally and theoretically investigated. The kneader enables high surface renewal and larger concentration gradients for the efficient mass transfer.