Synchronization of flexible sheets

It has been long known that drilling fluid viscoelastic properties have a significant impact on various elements of drilling hydraulics design (e.g., assessment of frictional pressure loss, particle settling velocity, hole cleaning, etc.). However, efforts for considering the viscoelastic fluid properties in drilling hydraulics design are traditionally hindered by the fact that there was no practical methodology to measure these critical fluid properties in the field. Previous studies have highlighted the advantages of using the concept of “energy dissipation” for the quantitative evaluation of fluid elasticity. Energy dissipation theory provides a more comprehensive description of the fluid elasticity by considering the two characteristics of the fluid simultaneously; stretchiness (oscillation strain % at the crossover point of G’ and G” curves) and the stress corresponding to crossover point (i.e., flow point). In a recent study, we have shown that the “energy dissipation” of viscoelastic fluids can be correlated to fluid physical properties such as apparent viscosity and funnel viscosity, which can be conveniently measured using standard field-testing equipment (i.e., Rotational Viscometer and Funnel viscometer). Based on these findings, a new methodology for the field assessment of drilling fluid viscoelasticity has been developed, opening new opportunities to develop improved hydraulics models. In this paper, using the new methodology developed in a recent study, we present a new generalized model for the field assessment of the particle settling velocity in viscoelastic fluids. The main objectives of the study were to: 1) Develop a generalized model for the field assessment of particle settling velocity in shear-thinning viscoelastic fluids by using the energy dissipation concept as an indicator of the fluid viscoelasticity; 2) Investigate the significant factors that influence the particle settling velocity to help provide a solution to the potential problem encountered in field drilling operations. We prepared ten different fluids, which were divided into two groups based on their shear viscosity values. In each group, five fluids were having similar shear viscosity and variable elasticity values. Nineteen different spherical particles were used to conduct particle settling experiments with a density range from 2700 kg/m3 to 6000kg/m3 and a diameter range from 1mm to 4mm. Rheological characterizations of the fluids have been conducted by using funnel viscometer, API Rotational viscometer, controlled shear rate, and amplitude sweep test measurements. Based on the experimental results and theory of the particle settling in non-Newtonian fluids, we developed a new model that can be used for predicting particle settling velocity in viscoelastic fluids. The statistical analyses had shown that the root means square error and mean absolute percentage error of model predictions were 0.0032 m/s and 4.1 percent, respectively.

Sonochemistry and sonoelectrochemistry are typically undertaken in a bulk fluid with sonication of sufficient intensity to generate visible cavitation. Sonoelectrochemistry was undertaken in a thin layer of fluid with a quartz crystal oscillator. In the thin layer configuration, no cavitation is visible and mass transport is not impacted, but impacts on electron transfer kinetics are observed. Because there is no visible cavitation, cyclic voltammetric responses typical of a quiescent electrolyte are observed. From the voltammograms for species that undergo rapid heterogeneous electron transfer such as outer sphere Ru(bpy)₃²⁺⇌Ru(bpy)₃³⁺+e, voltammetric morphology is unchanged on sonication of a thin layer of fluid. For Fe³+e⇌ Fe² that undergoes quasireversible (slower) electron transfer under cyclic voltammetric perturbation, sonication in a thin layer is found to increase the rate of heterogeneous electron transfer by roughly an order of magnitude. Sonoelectrochemical catalysis for inherently slow heterogeneous electron transfer processes is generated and observed in a thin layer of electrolyte. In the experiments reported here, the fluid layer was less than the wavelength of sonication. The aqueous electrolyte contains redox species and acid. Experiments were undertaken at a platinum wire electrode using a 41 kHz quartz crystal oscillator. For the same experimental conditions, no impact on the electron transfer reversible Ru(bpy)₃²⁺ was observed. All data were collected at a fixed frequency; impacts varied with oscillator intensity. As with many sonoelectrochemical experiments, subtle variation in experimental parameters complicate generation of reproducible results. Here, data generated by two different experimentalists yield similar outcomes. Best operating conditions differed slightly for the two experimentalists but the pattern of increased interfacial electron transfer rates for iron on sonication was found by both. Reference [1] Johna Leddy, Chester G. Duda, Jacob Lyon, and William J. Leddy III, "Thin Layer Sonoelectrochemistry and Sonoelectrochemistry Devices and Methods," published 28 May 2015 as US Patent Application 20150147594 A1.

An energy model for the transient flow boiling crisis under highly subcooled conditions at atmospheric pressure

In order to predict the fluid in thin layer precisely, this paper proposed a high-resolution method for fluid prediction. The method used geostatistical inversion with lithology masks to calculate water saturation. We applied this method to theoretical model and real data. The result was compared with that of prestack AVA simultaneous inversion for fluid prediction. It showed that this method had high resolution both in vertical and lateral directions for fluid prediction and could also predict the fluid in thin layer efficiently.

We consider the flow of two immiscible fluids lying between concentric cylinders when the outer cylinder is fixed and the inner one rotates. The interface is assumed to be concentric with the cylinders, and gravitational effects are neglected. We present a numerical study of the effect of different viscosities, different densities and surface tension on the linear stability of the Couette flow. Our results indicate that, with surface tension, a thin layer of the less-viscous fluid next to either cylinder is linearly stable and that it is possible to have stability with the less dense fluid lying outside. The stable configuration with the less-viscous fluid next to the inner cylinder is more stable than the one with the less-viscous fluid next to the outer cylinder. The onset of Taylor instability for one-fluid flow may be delayed by the addition of a thin layer of less-viscous fluid on the inner wall and promoted by a thin layer of more-viscous fluid on the inner wall.

Experimental investigation of surface instability of a thin layer of a magnetic fluid

The most obvious symmetry breaking in Nature is the left-right asymmetry of living beings: sugars and amino acids are almost exclusively represented by one of their stereoisomers (D-isomer for sugars and L-isomer for amino acids) at the expense of other possible isomers. In our experiment we studied the aqueous solutions of tartaric acid, alanine, and cysteine in the function of temperature by positron lifetime spectroscopy. The results were compared with those obtained in pure water under similar conditions. We always observed a sharp minimum of the positron lifetime at around 41 °C in water and in the solutions of the natural stereo-isomers. On the other hand, the same minimum occurred at considerably lower temperatures in the solutions of the “unnatural” isomers.

On closer analysis, the apparently simple act of sliding two contacting substrates relative to one another reveals a myriad of fundamental physical questions that have a broad technical application. Present semiconductor manufacturing imperatives require that planarization uniformity be maintained over length scales spanning 8 orders of magnitude, 1 from gate lengths of 32 nm to wafer diameters of 300 mm. Economic realities continue to drive yield targets ever higher. In this environment, process engineers seek to improve all manufacturing techniques, including chemical mechanical planarization CMP. Stick-slip behavior, and the large lateral forces associated with it, is an indication of reduced polish quality. 2,3 Stick-Slip As two surfaces slide past one another, their relative motion can be categorized into two regimes. The smooth polishing regime exhibits a stable, unchanging relative velocity, whereas stick-slip is identified by a relative velocity that alternates between near zero and some nonzero value at a high frequency. Hence, the stick-slip name, the surface alternates between sticking to the substrate and sliding past the substrate. 4 In many applications, to avoid stick-slip, a thin layer of fluid is introduced between the two surfaces, eliminating contact. This relative motion in which one surface is supported by a thin fluid layer is often characterized as hydrodynamic lubrication. 5 However, material removal during CMP requires some degree of contact; thus, process engineers must walk a fine line between acceptable contact and removal rates vs unacceptably high contact and the resultant stick-slip. 6,7 Intuitively, it is easy to postulate an increase in defectivity and reduction in polish quality resulting from stick-slip. Nevertheless, literature is sparse in this regard, indicating a possible avenue for investigation. CoF

Understanding the properties of hydraulic fractures, for example their growth mechanism, is a main task in their investigation. We model a hydraulic fracture by a thin layer of an ideal fluid which is embedded between an elastic and isotropic solid with identical properties on each side of the crack. The main goal of this work is to find reflection coefficients for a wave reflected at this thin fluid layer. We present full analytical solutions for the reflections of an incident P-wave, the P-P and P-S reflection coefficients, as well as for an incident S-wave, the S-S and S-P reflection coefficients. We find that for parameters in the range of microseismic needs, which means a layer thickness of h=0.001-0.01m and frequencies of f=50-400Hz, the reflection coefficients change with Poisson's ratio. Furthermore the reflections of an incident S-wave are significantly high. This allows us to image hydraulic fractures using microseismic events as a source. The results presented in this paper will help to understand the properties of hydraulic fractures and can be used to characterize reservoirs or improve the imaging of hydraulic fractures.

We model a hydraulic fracture by a thin layer of an ideal fluid which is embedded between an elastic and isotropic solid with identical properties on each side of the crack. The main goal is to describe and analyze reflection coefficients for a wave reflected at this thin fluid layer. We present full analytical solutions for the reflections of an incident P-wave, the P-P and P-S reflection coefficients, as well as for an incident S-wave, the S-S and S-P reflection coefficients. We find that for parameters in the range of microseismic needs, which means a layer thickness of h = 0.001 − 0.01m and frequencies of f = 50 − 400Hz, reflection coefficients of an incident S-wave are remarkably high. This allows us to image hydraulic fractures using microseismic events as a source. It also suggests to solve the inverse problem, which means to interpret reflection coefficients extracted from microseismic data in terms of reservoir properties. We compare the analytical solutions for the P-P reflections with synthetic data that is derived using Finite Difference modeling and find that the modeling confirms our theoretical approach.

A theoretical description of the low-Reynolds-number collision and rebound of two rigid or elastic spheres separated by a thin layer of viscous fluid with pressure-dependent physical properties is presented. It has previously been shown by Davis et al. (1986) that the hydrodynamic pressure which builds up in the thin fluid layer must become large enough to elastically deform the spheres near the axis of symmetry, if they are to rebound subsequent to colliding. Under these extreme pressures, however, it is expected that the fluid may also compress and that its viscosity may increase by several orders of magnitude. It is shown that these pressure-dependent effects may significantly alter the minimum separation reached during approach of the spheres, as well as the maximum separation and relative velocity attained during rebound of the spheres. In particular, the pressure buildup during the collision process is predicted to become sufficiently large under some conditions so that the corresponding viscosity increase causes the fluid in the gap between the colliding spheres to behave nearly as a solid and to limit the close approach of the opposing surfaces. Also, the storage of energy via the compression of the fluid in the gap allows rigid spheres to bounce as this energy is released subsequent to their collision. However, it is found that this rebound is very weak relative to that which is predicted for elastic spheres.

We present a microscopic model of the interface between liquid water and a hydrophilic, solid surface, as obtained from ab initio molecular dynamics simulations. In particular, we focused on the (100) surface of cubic SiC, a leading semiconductor candidate for biocompatible devices. Our results show that in the liquid in contact with the clean substrate, molecular dissociation occurs in a manner unexpectedly similar to that observed in the gas phase. After full hydroxylation takes place, the formation of a thin (approximately 3 A) interfacial layer is observed, which has higher density than bulk water and forms stable hydrogen bonds with the substrate. The presence of this thin layer points at rather weak effects on the structural properties of water induced by a one-dimensional confinement between approximately 1.3 nm hydrophilic substrates. In addition, our results show that the liquid does not uniformly wet the surface, but molecules preferably bind along directions parallel to the Si dimer rows.

In this paper we consider a strongly coupled fourth order parabolic system modelling the motion of two thin fluid layers in the presence of gravity and surface tension. In the non-degenerate case we prove existence and uniqueness of strong solutions and study the stability of the equilibria for various fluid–fluid configurations.

Waves in thin fluid layers are important in various stellar and planetary problems. Due to rapid rotation such systems will become oblate, with a latitudinal variation in the gravitational acceleration across the surface of the object. In the case of accreting neutron stars, rapid rotation could lead to a polar radius smaller than the equatorial radius by a factor ∼0.8. We investigate how the oblateness and a changing gravitational acceleration affect different hydrodynamic modes that exist in such fluid layers through analytic approximations and numerical calculations. The wave vectors of g modes and Yanai modes increase for more oblate systems compared to spherical counterparts, although the impact of variations in the changing gravitational acceleration is effectively negligible. We find that for increased oblateness, Kelvin modes show less equatorial confinement and little change in their wave vector. For r modes, we find that for more oblate systems the wave vector decreases. The exact manner of these changes for the r modes depends on the model for the gravitational acceleration across the surface.

Upon the impact of a droplet onto a thin fluid layer, the fluid is pushed away around the impact point until it reaches a certain radius to go upward to form a thin liquid wall. At the tip of the liquid wall, the circumferential instability creates a several droplets, which is commonly known as The size and the height of the crown and the number of the tip droplets are affected by the conditions of a droplet and of a fluid layer. Presently, the fundamental characteristics of the milk crown have been extensively investigated based on the flow visualization by the high-speed camera. Moreover, the motions of the fluid layer and the liquid film have been measured with the aid of PIV. The result reveals several interesting features of the formation of a milk crown.