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This study examines the flow behavior as well as the cuttings transport of non-Newtonian drilling fluid in the geometry of an eccentric annulus, accounting for what impacts drill pipe rotation might have on fluid velocity, as well as annular eccentricity on axial and tangential distributions of velocity. A two-phase Eulerian–Eulerian model was developed by using computational fluid dynamics to simulate drilling fluid flow and cuttings transport. The kinetic theory of granular flow was used to study the dynamics and interactions of cuttings transport. Non-Newtonian fluid properties were modeled using power law and Bingham plastic formulations. The simulation results demonstrated a marked improvement in efficiency, as much as 45%, in transport by increasing the fluid inlet velocity from 0.54 m/s to 2.76 m/s, reducing the amount of particle accumulation and changing axial and tangential velocity profiles dramatically, particularly at narrow annular gaps. At a 300 rpm rotation, the drill pipe brought on a spiral flow pattern, which penetrated tangential velocities in the narrow gap that had increased transport efficiency to almost 30% more. Shear-thinning behavior characterizes fluid of which the viscosity, at nearly 50% that of the central core low-shear regions, was closer to the wall high-shear regions. Fluid velocity and drill pipe rotation play a crucial role in optimizing cuttings transport. Higher fluid velocities with controlled drill pipe rotation enhance cuttings removal and prevent particle build-up, thereby giving very useful guidance on how to clean the wellbore efficiently in drilling operations. [ABSTRACT FROM AUTHOR]

The velocity distribution of flow in an eccentric cylindrical annulus is determined in an attempt to investigate the vertical capillary rise in the channel. The critical values of the radii ratio and the eccentricity at which the capillary rise changes from oscillatory to monotone or vice versa are determined. For a particular aspect ratio, the rise becomes monotonic as the eccentricity increases. The oscillations are also dampened as the annulus becomes thinner. These critical values depend on Galileo and Bond numbers as well as the contact angle. The results reduce to the limiting cases of concentric and fully eccentric annuli. The critical values are also calculated for the special arrangements when the radii ratios are 1 and 0. The latter limit is in perfect agreement with the conditions found in the literature for the classical circular channel. [ABSTRACT FROM AUTHOR]

The present study presents a computational investigation into the thermal mixing along with entropy generation throughout the natural convection flow within an arbitrarily eccentric annulus. Salt water is filled inside the eccentric annulus, in which the outer and inner cylinders have T c and T h constant temperatures. The Boussinesq approximation is used to develop the governing equations for the natural convection flow, which are then solved on a structured quadrilateral mesh using the OpenFOAM software package (FOAM-Extend 4.0). The computational simulations are performed for Rayleigh numbers ( R a = 10 3 – 10 5 ), eccentricity ( ϵ = 0 , 0.4 , 0.8 ), angular positions ( φ = 0 ∘ , 45 ∘ , 90 ∘ ), and Prandtl number ( P r = 10 , salt water). The computational results are visualized in terms of streamlines, isotherms, and entropy generation caused by fluid friction and heat transfer. Additionally, a thorough examination of the variations in the average and local Nusselt numbers, circulation intensity with eccentricities, and angular positions is provided. The optimal state of heat transfer is shown to be influenced by the eccentricity, angular positions, uniform temperature sources, and Boussinesq state. Moreover, the rate of thermal mixing and the production of total entropy increase as R a increases. It is found that, compared to a concentric annulus, an eccentric annulus has a higher rate of thermal mixing and entropy generation. The findings show which configurations and types of eccentric annulus are ideal and could be used in any thermal processing activity where a salt fluid ( P r = 10 ) is involved. [ABSTRACT FROM AUTHOR]

The capillary-driven flow is an essential portion of liquid behavior under microgravity. Capillary-driven flows in eccentric annuli under microgravity are deeply analyzed in this paper. A second-order differential equation for the climbing height of liquid is derived. It can be solved with the Runge–Kutta method with appropriate initial conditions. The influences of the dynamic angle, the friction force on the annulus wall and the liquid meniscus in the reservoir on liquid behaviors are all considered in this paper. Moreover, effects of eccentricity on flow resistance and flow speed are discussed. This study has been verified by numerical simulation with the volume of fluid method. [ABSTRACT FROM AUTHOR]

Copyright of Drilling Fluid & Completion Fluid is the property of Drilling Fluid & Completion Fluid Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The gas lift plunger uses the pressure difference between bottom hole and wellhead to drive the plunger and accumulated liquid to move along the wellbore, which can achieve the purpose of drainage and gas recovery. At present, few studies pay attention to the influence of dynamic eccentricity between the plunger and tubing in the rising course. In this paper, the transient numerical calculation method of gas–liquid two-phase flow was used to study the movement of the plunger under different eccentricities. The results show that the sealing effect of the plunger gradually deteriorates with the increase of the eccentricity. When the plunger axis coincides with the tubing axis, the sealing effect of the turbulence groove can achieve the requirements of plunger lift. When the eccentricity is 1.5 mm, the liquid leakage rate increases by 156.64% compared with concentric state, and the liquid in the upper part of the plunger leaks at a rate of 0.29 kg/s. In addition, the process efficiency of plunger in the eccentric state is significantly reduced based on two aspects that lifting kinetic energy and liquid lifting ability. When the eccentricity is 1.5 mm, pressure difference between the top and bottom of the plunger is reduced by 17.5% compared with the concentric state, and the drainage quality is reduced by 27.8%. [ABSTRACT FROM AUTHOR]

Copyright of Science Technology & Industry / Keji he Chanye is the property of Chinese Society of Technology Economics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, we investigate the first Steklov–Dirichlet eigenvalue on eccentric annuli. The main geometric parameter is the distance t between the centers of the inner and outer boundaries of an annulus. We first show the differentiability of the eigenvalue in t and obtain an integral expression for the derivative value in two and higher dimensions. We then derive an upper bound of the eigenvalue for each t, in two dimensions, by the variational formulation. We also obtain a lower bound of the eigenvalue, given a restriction that the two boundaries of the annulus are sufficiently close. The key point of the proof of the lower bound is in analyzing the limit behavior of an infinite series expansion of the first eigenfunction in bipolar coordinates. We also derive a relation between the first eigenvalue and a sequence of eigenvalues obtained by a finite section method. Based on this relation, we also perform numerical experiments that exhibit the monotonicity for two dimensions. [ABSTRACT FROM AUTHOR]

Accurately predicting pressure gradient with inner pipe rotation in concentric or eccentric annuli can provide a theoretical foundation to evaluate equivalent mud weight for avoiding downhole problems caused by overlarge downhole pressure, such as: gas kick, lost circulation, even blowout. Nowadays, many studies were carried out on the basis of theoretical and experimental researches to investigate the laminar helical flow in concentric/eccentric annuli, however, to the best of our knowledge, no simplified model has been reported to predicting pressure gradient (PG) in eccentric annuli with inner pipe rotation for yield-power-law (YPL) fluids. In this paper, a simplified modeling for predicting PG of laminar helical flow in an eccentric annulus with YPL fluids has been established. In addition, the validation of simplified model has been investigated by comparing results with computational fluid dynamic (CFD) simulations, existing experimental measurements and numerical model. Predictions of the simplified model shown good agreement with CFD and experimental results within ±10% error bars for power-law and YPL fluids both in concentric and eccentric annuli. [ABSTRACT FROM AUTHOR]

Eccentric annular regions formed by two impermeable cylinders are considered. Flow of Newtonian fluid in the annular region in the presence of heat transfer is studied. The eccentric annulus is mapped to concentric annular region through conformal mapping. Analytical solution for both temperature and velocity is obtained and graphically depicted. An increase in eccentricity results in an increase in velocity but a decrease in temperature. [ABSTRACT FROM AUTHOR]

This work is about studying the natural convection of 3-D steady-state non-Newtonian power law fluid numerically. The inner cylinder was put eccentrically into the outer one. The cylinders are held at constant temperatures with the inner one heated isothermally at temperature, Th, and the outer one cooled isothermally at temperature Tc (Th > Tc). The simulations have been taken for the parameters 10³ ≤ Ra ≤ 105, 10 ≤ Pr ≤ 10³, 0.6 ≤ n ≤ 1.4, and 0 ≤ ɛ ≤ 0.9, and an inclination angle, ϕ, from 0° to 90°. The average Nusselt numbers for the previous parameters are obtained and discussed numerically. The results revealed that the average Nusselt number has the highest values when n = 0.6, Ra = 105 at ϕ = 0 which is a signal for the large transfer herein and has the lowest values for n = 1.4, Ra = 10³, at ϕ = 90° which is a signal that the transfer is by conduction more than convection. Furthermore, the increasing of eccentricity causes an increase in the Nusselt number for all the cases. Finally, the best case where we can get the best heat transfer is at ϕ = 0, ɛ = 0.9 among them all. The results have compared with some precedent works and showed good agreement. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Petroleum Research & Studies is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The two-dimensional time-dependent natural convection heat transfer of non-Newtonian nanofluids is studied numerically between the gap of two horizontal cylinders. The inner and outer cylinders were kept at T i and T o ( T i > T o ), respectively. The finite volume technique was used in the study. The effects of Ra number ( 10 3 ≤ R a ≤ 10 6 ), aspect ratio ( 0.4 ≤ AR ≤ 1.2 ), power law index of the nanofluid ( 0.6 ≤ n ≤ 1.4 ), horizontal eccentricity ( 0.2 ≤ ε H ≤ 0.8 ), vertical eccentricity ( - 0.8 ≤ ε v ≤ + 0.8 ) and rotation of the inner cylinder ( 0 ≤ ω ≤ 500 ) on the flow field and heat transfer were investigated. It was found that a very good agreement exists with the present numerical results and the results of the open literature. The results indicate that with increasing the Ra number from 10 3 to 10 6 the heat transfer increases by about 80%. The increase in aspect ratio also increases the heat transfer. The results showed that with increasing the power law index from 0.6 to 1.4, the heat transfer decreases by a rate of about 78%. In addition, the time to reach steady-state conditions increases with increasing power law index. Simulations were performed for a power law index of 0.8 to investigate the effect of eccentricity of the inner cylinder, and it was observed that the heat transfer is higher for negative vertical eccentricities, and the time to reach steady conditions shortens with the effect of negative vertical eccentricity and power law index. [ABSTRACT FROM AUTHOR]

A numerical study of mixed convection flow and heat transfer of copper-water nanofluid inside an eccentric horizontal annulus is presented. The inner and outer cylinders are kept at constant temperatures as Th and Tc, respectively. The inner cylinder rotates to generate the forced convection effect. The numerical work was carried out using an in-house CFD code written in FORTRAN. Different scenarios were explored to explain the effects of different parameters on the studied problem. These parameters are Richardson number, eccentricity ratio, and solid volume fraction. The range of the Richardson number, solid volume fraction of the nanoparticles, and the eccentricity ratio, are 0.01 ≤ Ri ≤ 100 (natural convection), 0 ≤ ζ ≤ 0.05, 0 ≤ ε ≤ 0.9, respectively. All results were performed with thermal Grashof number, and radius ratio Rr, equaled to 104 and 2, respectively. The effects of eccentricity, nanoparticles volume fraction, and Richardson number on the average Nusselt number, streamlines and isotherms were investigated. Results were discussed, and were found to be in good agreement with previous works. It was also found that, the eccentricity has a positive remarkable effect on the average Nusselt number, while the effect of nanoparticles concentration was more pronounced at mixed convection region (Ri = 1). [ABSTRACT FROM AUTHOR]

Cuttings transport experiment device for extended-reach horizontal well was established based on the similarity system theory. The parameters similarity between the model and the prototype was deduced using the similar particle Reynolds number. Then, research was made on the variation of 10 parameters(i.e. annular velocity, mud density and effective viscosity, cuttings density and size, drillpipe rotation speed and eccentricity, inclination angle, rate of penetration and borehole size) with the dimensionless cutting-bed thickness. On this basis, a steady dimensionless cutting-bed thickness equation for extended-reach horizontal well was established with the nonlinear regression method, and the model was veriifed through literatures. The model provides a signiifcant guidance for borehole cleaning of minimum cuttings transport lfux and the optimization of ROP for extended-reach horizontal wells. [ABSTRACT FROM AUTHOR]

Slow-flow drilling fluid caused by fingering instability of displacement interface is the main factor to result in oil/gas/ water channeling. The displacement interface in horizontal wells is affected by resistance effect in narrow and wide clearances caused by casing eccentricity and buoyancy effect caused by density difference. Besides, impacts of the two factors on displacement interface are opposite. Therefore, displacement interface stability can be enhanced by optimizing the density difference of displacing fluids based on casing eccentricity in horizontal wells. The change law of the displacement interface length with time is analyzed based on the advantages and disadvantage of the method of three-dimensional numerical simulation to realize the target of minimum displacement interface length and have the matching relationship between the optimal density difference and casing eccentricity. The conclusions are as follows: the growth rate of displacement interface length slows down with time increasing, but it is not obvious; the too large or small density difference will reduce the displacement interface stability in the eccentric annulus of horizontal wells. In order to achieve the shortest displacement interface length in cementing, reasonable density difference shall be chosen on the basis of casing eccentricity. The study results provides theoretical basis for the design of displacement parameters and cementing length in horizontal wells. [ABSTRACT FROM AUTHOR]

Viscous incompressible fluid flow along the clearance between two parallel eccentric circular cylinders is studied numerically. The geometric parameters and the Reynolds number are taken so that the turbulent flow regime takes place in a part of flow, namely, in the zone where the clearance is wide, while the low is laminar in the narrow clearance zone. Criteria using which these zones can be distinguished are discussed. [ABSTRACT FROM AUTHOR]

Accurate estimation of the frictional pressure losses for non-Newtonian drilling fluids inside annulus is quite important to determine pump rates and select mud pump systems during drilling operations. The purpose of this study is to estimate frictional pressure loss and velocity profile of non-Newtonian drilling fluids in both concentric and eccentric annuli using an Eulerian-Eulerian computational fluid dynamics (CFD) model. An extensive experimental program was performed in METU-PETE Flow Loop using two non-Newtonian drilling fluids including different concentrations of xanthan biopolimer, starch, KCl and soda ash, weighted with barite for different flow rates and frictional pressure losses were recorded during each test. This study aims to simulate non-Newtonian fluids flow through both horizontal concentric and eccentric annulus and to predict frictional pressure losses using an Eulerian-Eulerian computational fluid dynamics (CFD) model. Computational fluid dynamic simulations were performed to compare with experimental data gathered at the METU-PETE flow loop and previous studies as well as slot flow approximation for the annulus. Results show that the computational fluid dynamic model simulations are capable of estimating frictional pressure drop with an error of less than 10% in most cases, more accurately than the slot equation. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT: In this article, the governing equations for the unsteady flow of viscoelastic fluid in the eccentric annulus with the inner cylinder reciprocating axially and the expression of the pressure distribution on the wall of the inner cylinder of the annulus are established and derived, respectively, under the bipolar coordinate system. The equations and the expression are solved and calculated numerically using the finite difference method, respectively. The curves of the pressure distribution on the wall of the inner cylinder of the aqueous solution of Hydrolyzed Polyacrylamide (HPAM) are plotted and the influences of annular eccentricity, stroke, and stroke frequency on the pressure distribution are analyzed. [Copyright &y& Elsevier]