Non-Isothermal Peristaltic Flow of Newtonian Fluids in a Circular Tube

2009 ◽  
Author(s):  
M. S. Yun ◽  
B. P. Huynh
Keyword(s):  
Reynolds Number ◽  
Flow Pattern ◽  
Circular Tube ◽  
Pressure Change ◽  
Peristaltic Flow ◽  
Isothermal Flow ◽  
Newtonian Fluids ◽  
Fluid Viscosity ◽  
Fluid Properties ◽  
Isothermal Case

Non-isothermal peristaltic flow of Newtonian fluids in a circular tube is investigated numerically, using a commercial Computational Fluid Dynamics (CFD) software package. Simulation is performed over a range of Reynolds-number values, up to 1000. Temperature affects the flow field via fluid viscosity, which is assumed to decrease exponentially with temperature. Other fluid properties are assumed to be constant, and are similar to those of an oil. Allowing for temperature effects alters significantly the flow pattern and reduces pressure change. In the crest region, recirculation appears in non-isothermal flow at a much smaller Reynolds number Re than in isothermal flow. Influence of the Reynolds number itself is also reduced significantly, such that the flow pattern changes very little with increasing Re, in contrast to the isothermal case. Similarly, in non-isothermal flow, flow pattern is unchanged at different flow rate. This is also in contrast to the isothermal situation.

A Numerical Study of Non-Isothermal Peristaltic Flow of Power-Law Fluids in a Circular Tube

2010 ◽  
Author(s):  
M. S. Yun ◽  
B. P. Huynh
Keyword(s):  
Reynolds Number ◽  
Power Law ◽  
Circular Tube ◽  
Numerical Study ◽  
Shear Thickening ◽  
Peristaltic Flow ◽  
Fluid Viscosity ◽  
Power Law Fluids ◽  
Fluid Behaviour ◽  
Power Law Index

Non-isothermal peristaltic flow of power-law fluids in a circular tube is investigated numerically, using a commercial Computational Fluid Dynamics (CFD) software package that employs the Finite Volume Method. Simulation is performed over the range of Reynolds-number values from 1 to 100. Temperature effect on the flow field is via fluid viscosity, which is assumed to decrease exponentially with temperature. Also, except for viscosity, other fluid properties are assumed to be constant, and are similar to those of an oil. Over a range of the power-law index covering fluid behaviour from shear-thinning, through Newtonian, to shear-thickening, it is found that allowing for temperature effects has significantly altered the flow pattern and pressure variation, even when the corresponding changes in temperature itself are small. Around the crest region, recirculation appears in non-isothermal flow at all power-law-index and Reynolds-number values considered in this work, in contrast to isothermal situations.

Evaluation of Pressure Change While Steady-State Tripping

2014 ◽  
Author(s):  
Evgeny Podryabinkin ◽  
Ramadan Ahmed ◽  
Vladimir Tarasevich ◽  
Roland May
Keyword(s):  
Steady State ◽  
Numerical Solutions ◽  
Pressure Change ◽  
Laminar Flows ◽  
New Method ◽  
Analytical Models ◽  
Fluid Viscosity ◽  
Operational Parameters ◽  
Cylindrical Annulus ◽  
Fluid Properties

Excessive tripping speed in an uncased borehole increases the risk of having formation damage or influx of formation fluid (kick). However, if the tripping is performed at lower speeds, the operation requires more rig time. Hence, increased trip speed cuts expensive rig time. These opposing goals require thorough planning and optimization of the tripping operation to avoid operational problems and reduce financial expenditures. To maximize the tripping speed, accurate prediction of the pressure change occurring due to the axial pipe movement (surge or swab pressure) is necessary. The pressure change is influenced by the hole and string diameters, eccentricity, fluid properties and trip speed. The tripping speed is one of the operational parameters, which are regularly adjusted at the rig site. Analytical solutions exist only for special scenarios. The semi-analytical models for calculation of the steady-state pressure change cannot provide accurate predictions. They are mostly based on disputable assumptions which make the model to underestimate the pressure change. Most of the existing models are based on the parallel-plate approximation of the annular geometry. In another approach, the parameter, which reflects the amount of fluid which is dragged the direction of the string, assumed to be constant or calculated independent of the fluid viscosity. In this paper, accurate solutions were obtained from direct numerical simulation of flow in a cylindrical annulus with axial movement of the inner cylinder. The numerical algorithm is based on finite volume method and incorporates laminar flows of Newtonian, Power Law, Bingham Plastic and Herschel-Bulkley fluids. The method predicts the pressure change occurring in concentric and eccentric annuli with and without rotation of the inner cylinder. The goals of this work are to: i) study the influence of the eccentricity, fluid properties and tripping speed on the pressure change; and ii) evaluate the accuracy of the simplified approaches by comparing experimental data and numerical solutions, and determine their validity ranges. This paper presents a new method for finding trip-caused pressure change in the wellbore through systematic analysis of the numerical solutions. Parametric study was performed to examine the effects of different influential parameters on the pressure change. In addition, the results obtained from the numerical method are compared with the simplified solutions and the discrepancies are analyzed to show the improved accuracy of the new method.

Entry Flow in a Circular Tube of Aortic Arch Dimensions

1984 ◽  
Vol 106 (4) ◽  
pp. 351-356
Author(s):  
K. O. Lim ◽  
J. S. Kennedy ◽  
C. M. Rodkiewicz
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Secondary Flow ◽  
Flow Pattern ◽  
Aortic Arch ◽  
Steady Flow ◽  
Circular Tube ◽  
Boundary Layer Separation ◽  
Curved Tube ◽  
Separation Zones

Steady flow within a uniform circular curved tube formed by two 90-deg elbows was studied as a function of ψ, the angle between the planes of curvature of the two elbows. Boundary layer separation was found at two locations. The sites of these separation zones were observed to be essentially independent of ψ while the Reynolds number at which separation was first detected was found to decrease as ψ increased. The relation between separation and the pathogenesis of atherosclerosis is discussed. Secondary flow pattern was found to depend on ψ and in some instances on Reynolds number as well.

Influence of viscosity temperature dependence on the spectral characteristics of the thermoviscous liquids flow stability equation

2019 ◽  
Vol 14 (1) ◽  
pp. 52-58 ◽  
Author(s):  
A.D. Nizamova ◽  
V.N. Kireev ◽  
S.F. Urmancheev
Keyword(s):  
Reynolds Number ◽  
Spectral Characteristics ◽  
Wave Number ◽  
Critical Parameters ◽  
Fluid Viscosity ◽  
Flat Channel ◽  
Stability Equation ◽  
The Stability ◽  
Thermoviscous Fluid ◽  
Sommerfeld Equation

The flow of a viscous model fluid in a flat channel with a non-uniform temperature field is considered. The problem of the stability of a thermoviscous fluid is solved on the basis of the derived generalized Orr-Sommerfeld equation by the spectral decomposition method in Chebyshev polynomials. The effect of taking into account the linear and exponential dependences of the fluid viscosity on temperature on the spectral characteristics of the hydrodynamic stability equation for an incompressible fluid in a flat channel with given different wall temperatures is investigated. Analytically obtained profiles of the flow rate of a thermovisible fluid. The spectral pictures of the eigenvalues of the generalized Orr-Sommerfeld equation are constructed. It is shown that the structure of the spectra largely depends on the properties of the liquid, which are determined by the viscosity functional dependence index. It has been established that for small values of the thermoviscosity parameter the spectrum compares the spectrum for isothermal fluid flow, however, as it increases, the number of eigenvalues and their density increase, that is, there are more points at which the problem has a nontrivial solution. The stability of the flow of a thermoviscous fluid depends on the presence of an eigenvalue with a positive imaginary part among the entire set of eigenvalues found with fixed Reynolds number and wavenumber parameters. It is shown that with a fixed Reynolds number and a wave number with an increase in the thermoviscosity parameter, the flow becomes unstable. The spectral characteristics determine the structure of the eigenfunctions and the critical parameters of the flow of a thermally viscous fluid. The eigenfunctions constructed in the subsequent works show the behavior of transverse-velocity perturbations, their possible growth or decay over time.

scholarly journals Turbulence kinetic energy exchanges in flows with highly variable fluid properties

2017 ◽  
Vol 834 ◽  
pp. 5-54 ◽  
Author(s):  
Dorian Dupuy ◽  
Adrien Toutant ◽  
Françoise Bataille
Keyword(s):  
Reynolds Number ◽  
Temperature Gradient ◽  
Velocity Fluctuation ◽  
Spectral Studies ◽  
Spectral Energy ◽  
Correlation Tensor ◽  
Variable Fluid Properties ◽  
Fluid Properties ◽  
Energy Exchanges ◽  
The Mean

This paper investigates the energy exchanges associated with the half-trace of the velocity fluctuation correlation tensor in a strongly anisothermal low Mach fully developed turbulent channel flow. The study is based on direct numerical simulations of the channel within the low Mach number hypothesis and without gravity. The overall flow behaviour is governed by the variable fluid properties. The temperature of the two channel walls are imposed at 293 K and 586 K to generate the temperature gradient. The mean friction Reynolds number of the simulation is 180. The analysis is carried out in the spatial and spectral domains. The spatial and spectral studies use the same decomposition of the terms of the evolution equation of the half-trace of the velocity fluctuation correlation tensor. The importance of each term of the decomposition in the energy exchanges is assessed. This lets us identify the terms associated with variations or fluctuations of the fluid properties that are not negligible. Then, the behaviour of the terms is investigated. The spectral energy exchanges are first discussed in the incompressible case since the analysis is not present in the literature with the decomposition used in this study. The modification of the energy exchanges by the temperature gradient is then investigated in the spatial and spectral domains. The temperature gradient generates an asymmetry between the two sides of the channel. The asymmetry can in a large part be explained by the combined effect of the mean local variations of the fluid properties, combined with a Reynolds number effect.

scholarly journals Second Law Analysis of Laminar Flow in a Circular Pipe Immersed in an Isothermal Fluid

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Vishal Anand ◽  
Krishna Nelanti
Keyword(s):  
Laminar Flow ◽  
Entropy Generation ◽  
Circular Tube ◽  
Dimensionless Temperature ◽  
Bejan Number ◽  
Uniform Wall Temperature ◽  
Thermal Boundary Conditions ◽  
Fluid Properties ◽  
Isothermal Fluid ◽  
Uniform Wall

Entropy generation and pumping power to heat transfer ratio (PPR) of a laminar flow, for a circular tube immersed in an isothermal fluid, are studied analytically in this paper. Two different fluids, namely, water and ethylene glycol, are chosen to study the influence of fluid properties on entropy generation and PPR. The expressions for dimensionless entropy generation, Bejan number and PPR are derived in a detailed way and their variations with Reynolds number, external Biot number, and the dimensionless temperature difference are illustrated. The results of the analysis are compared with those for a laminar flow in a circular tube with uniform wall temperature boundary condition. Finally, a criterion is established to determine which type of thermal boundary conditions is more suitable for a particular fluid, with respect to its influence on entropy generation.

Relationship of Pulmonary Venous Flow Pattern to Mean Left Atrial Pressure and Phasic Pressure Change

Cardiology ◽  
1996 ◽  
Vol 87 (3) ◽  
pp. 224-229 ◽  
Author(s):  
Jer-Min Lin ◽  
Yi-Heng Li ◽  
Kwan-Lih Hsu ◽  
Juey-Jen Hwang ◽  
Yung-Zu Tseng
Keyword(s):  
Flow Pattern ◽  
Left Atrial ◽  
Pressure Change ◽  
Atrial Pressure ◽  
Left Atrial Pressure ◽  
Venous Flow ◽  
Pulmonary Venous Flow ◽  
Relationship Of

Settling Behavior of Particles in Bubble Containing Newtonian Fluids: Experimental Study and Model Development

2021 ◽  
Author(s):  
Silin Jing ◽  
Xianzhi Song ◽  
Zhaopeng Zhu ◽  
Buwen Yu ◽  
Shiming Duan
Keyword(s):  
Reynolds Number ◽  
Drag Coefficient ◽  
Volume Concentration ◽  
Settling Velocity ◽  
Particle Density ◽  
Particle Diameter ◽  
Newtonian Fluids ◽  
Spherical Particles ◽  
Bubble Volume ◽  
Particle Reynolds Number

Abstract Accurate description of cuttings slippage in the gas-liquid phase is of great significance for wellbore cleaning and the control accuracy of bottom hole pressure during MPD. In this study, the wellbore bubble flow environment was simulated by a constant pressure air pump and the transparent wellbore, and the settling characteristics of spherical particles under different gas volume concentrations were recorded and analyzed by highspeed photography. A total of 225 tests were conducted to analyze the influence of particle diameter (1–12mm), particle density (2700–7860kg/m^3), liquid viscosity and bubble volume concentration on particle settling velocity. Gas drag force is defined to quantitatively evaluate the bubble’s resistance to particle slippage. The relationship between bubble drag coefficient and particle Reynolds number is obtained by fitting the experimental results. An explicit settling velocity equation is established by introducing Archimedes number. This explicit equation with an average relative error of only 8.09% can directly predict the terminal settling velocity of the sphere in bubble containing Newtonian fluids. The models for predicting bubble drag coefficient and the terminal settling velocity are valid with particle Reynolds number ranging from 0.05 to 167 and bubble volume concentration ranging from 3.0% to 20.0%. Besides, a trial-and-error procedure and an illustrative example are presented to show how to calculate bubble drag coefficient and settling velocity in bubble containing fluids. The results of this study will provide the theoretical basis for wellbore cleaning and accurate downhole pressure to further improve the performance of MPD in treating gas influx.

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