Annular Extrudate Swell of Newtonian Fluids Revisited: Extended Range of Compressible Simulations

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Evan Mitsoulis
Keyword(s):  
Full Range ◽  
Thickness Swell ◽  
Newtonian Fluids ◽  
Outer Diameter ◽  
Extrudate Swell ◽  
Pressure Losses ◽  
Weakly Compressible ◽  
Compressibility Coefficient ◽  
Limited Length ◽  
Parameter Values

In a recent article (Mitsoulis, 2007, “Annular Extrudate Swell of Newtonian Fluids: Effects of Compressibility and Slip at the Wall,” ASME J. Fluids Eng., 129, pp. 1384–1393), numerical simulations were undertaken for the benchmark problem of annular extrudate swell of Newtonian fluids. The effects of weak compressibility and slip at the wall were studied through simple linear laws. While slip was studied in the full range of parameter values, compressibility was confined within a narrow range of values for weakly compressible fluids, where the results were slightly affected. This range is now markedly extended (threefold), based on a consistent finite element method formulation for the continuity equation. Such results correspond to foam extrusion, where compressibility can be substantial. The new extended numerical results are given for different inner/outer diameter ratios κ under steady-state conditions for Newtonian fluids. They provide the shape of the extrudate, and, in particular, the thickness and diameter swells, as a function of the dimensionless compressibility coefficient B. The pressures from the simulations have been used to compute the excess pressure losses in the flow field (exit correction). As before, weak compressibility slightly affects the thickness swell (about 1% in the range of 0≤B≤0.02) mainly by a swell reduction, after which a substantial and monotonic increase occurs for B>0.02. The exit correction increases with increasing compressibility levels in the lower B-range and is highest for the tube (κ=0) and lowest for the slit (κ=1). Then it passes through a maximum around B≈0.02, after which it decreases slowly. This decrease is attributed to the limited length of the flow channel (here chosen to be eight die gaps).

Annular Extrudate Swell of Newtonian Fluids: Effects of Compressibility and Slip at the Wall

2007 ◽  
Vol 129 (11) ◽  
pp. 1384-1393 ◽  
Author(s):  
Evan Mitsoulis
Keyword(s):  
Thickness Swell ◽  
Diameter Ratio ◽  
Newtonian Fluids ◽  
Outer Diameter ◽  
The Finite Element Method ◽  
Slip Coefficient ◽  
Extrudate Swell ◽  
Pressure Losses ◽  
Pipe Extrusion ◽  
Slip Coefficients

Numerical simulations have been undertaken for the benchmark problem of annular extrudate swell present in pipe extrusion and parison formation in blow molding. The effects of weak compressibility and slip at the wall are studied through simple linear laws. The finite element method is used to provide numerical results for different inner/outer diameter ratios κ under steady-state conditions for Newtonian fluids. The present results provide the shape of the extrudate, and, in particular, the thickness and diameter swells, as a function of the dimensionless compressibility and slip coefficients, B and Bsl, respectively. The pressures from the simulations have been used to compute the excess pressure losses in the flow field (exit correction). Weak compressibility slightly affects the thickness swell (about 1% in the range of simulations 0⩽B⩽0.02) mainly by a swell reduction, while slip drastically reduces the swelling to 1–2% for obvious slip (Bsl≈1) and to 0 for perfect slip (Bsl>10). The exit correction increases with increasing compressibility levels and is highest for the tube (κ=0) and lowest for the slit (κ=1). It decreases monotonically to 0 as the dimensionless slip coefficient reaches its asymptotic limit of perfect slip. All results are ordered with the diameter ratio κ, between the limits of tube (κ=0) and slit (κ=1).

Simple Correlations and Analysis of Cuttings Transport With Newtonian and Non-Newtonian Fluids in Horizontal and Deviated Wells

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Mehmet Sorgun
Keyword(s):  
Pure Water ◽  
Newtonian Fluids ◽  
The Other ◽  
Cuttings Transport ◽  
Pressure Losses ◽  
Test Conditions ◽  
Bed Thickness ◽  
Solid Liquid ◽  
Cuttings Bed ◽  
Pipe Rotation

In this study, simple empirical frictional pressure losses and cuttings bed thickness correlations including pipe rotation are developed for solid-liquid flow in horizontal and deviated wellbores. Pipe rotation effects on cuttings transport in horizontal and highly inclined wells are investigated experimentally. Correlations are validated experimental data with pure water as well as four different non-Newtonian fluids for hole inclinations from horizontal to 60 degrees, flow velocities from 0.64 m/s to 3.56 m/s, rate of penetrations from 0.00127 to 0.0038 m/s, and pipe rotations from 0 to 250 rpm. Pressure drop within the test section, and stationary and/or moving bed thickness are recorded besides the other test conditions. The new correlations generated in this study are believed to be very practical and handy when they are used in the field.

Numerical Studies of the Effect of Constitutive Model Parameters as Reflecting Polymer Molecular Structure on Extrudate Swell

2002 ◽  
Vol 12 (5) ◽  
pp. 252-259 ◽  
Author(s):  
Nattapong Nithi-Uthai ◽  
Ica Manas-Zloczower
Keyword(s):  
Molecular Weight ◽  
Constitutive Model ◽  
Full Range ◽  
Constitutive Models ◽  
Model Parameters ◽  
Extrudate Swell ◽  
Relaxation Spectra ◽  
Shear Rates ◽  
Swell Ratio ◽  
Numerical Predictions

Abstract PolyFlow, a software package based on the finite element method was employed to simulate the extrudate swell for polybutadiene of various molecular weight (Mw) and molecular weight distribution (MWD). We calculated the relaxation spectra for the different samples and then inserted the spectra into a standard K-BKZ constitutive model used in the numerical simulations. Accurate predictions of MWD confirm the completeness of frequency range in the oscillatory shear experimental data. In turn, the wholeness of relaxation spectra as substantiated by MWD predictions, sustain the level of confidence when using constitutive models based on these spectra. We demonstrate the importance of using the full range of relaxation spectrum rather than a short range around typical shear rates for the accuracy of the numerical predictions. We found extrudate swell ratio (ESR) to be strongly dependent on MWD and stress conditions at the die exit.

scholarly journals The asymptotic iteration method for the angular spheroidal eigenvalues with arbitrary complex size parameter c

2006 ◽  
Vol 84 (2) ◽  
pp. 121-129 ◽  
Author(s):  
T Barakat ◽  
K Abodayeh ◽  
B Abdallah ◽  
O M Al-Dossary
Keyword(s):  
Excellent Agreement ◽  
Iteration Method ◽  
Full Range ◽  
Numerical Results ◽  
Asymptotic Iteration Method ◽  
Published Data ◽  
Size Parameter ◽  
Arbitrary Complex ◽  
Parameter Values

The asymptotic iteration method is applied to calculate the angular spheroidal eigenvalues [Formula: see text] (c) with arbitrary complex size parameter c. It is shown that the numerical results obtained for [Formula: see text] (c) are all in excellent agreement with the available published data over the full range of parameter values [Formula: see text] m, and c. Some representative values of [Formula: see text] (c) for large real c are also given.PACS No.: 02.70.–c.

THE ASYMPTOTIC ITERATION METHOD FOR THE EIGENENERGIES OF THE ASYMMETRICAL QUANTUM ANHARMONIC OSCILLATOR POTENTIALS $V(x)=\sum_{j=2}^{2\alpha}A_{j}x^{j}$

2007 ◽  
Vol 22 (01) ◽  
pp. 203-212 ◽  
Author(s):  
T. BARAKAT ◽  
O. M. AL-DOSSARY
Keyword(s):  
Rate Of Convergence ◽  
Iteration Method ◽  
Anharmonic Oscillator ◽  
Full Range ◽  
Adjustable Parameter ◽  
Numerical Results ◽  
Asymptotic Iteration Method ◽  
Anharmonic Oscillators ◽  
Parameter Values

The asymptotic iteration method is used to calculate the eigenenergies for the asymmetrical quantum anharmonic oscillator potentials [Formula: see text], with (α = 2) for quartic, and (α = 3) for sextic asymmetrical quantum anharmonic oscillators. An adjustable parameter β is introduced in the method to improve its rate of convergence. Comparing the present results with the exact numerical values, and with the numerical results of the earlier works, it is found that asymptotically, this method gives accurate results over the full range of parameter values Aj.

Modeling of Newtonian Fluids in Annular Geometries With Inner Pipe Rotation

2010 ◽  
Author(s):  
Mehmet Sorgun ◽  
Jerome J. Schubert ◽  
Ismail Aydin ◽  
M. Evren Ozbayoglu
Keyword(s):  
Axial Velocity ◽  
Pressure Loss ◽  
Tangential Velocity ◽  
Flow Characteristics ◽  
Newtonian Fluids ◽  
Flow Loop ◽  
Eccentric Annulus ◽  
Pressure Losses ◽  
Proposed Model ◽  
Pipe Rotation

Flow in annular geometries, i.e., flow through the gap between two cylindrical pipes, occurs in many different engineering professions, such as petroleum engineering, chemical engineering, mechanical engineering, food engineering, etc. Analysis of the flow characteristics through annular geometries is more challenging when compared with circular pipes, not only due to the uneven stress distribution on the walls but also due to secondary flows and tangential velocity components, especially when the inner pipe is rotated. In this paper, a mathematical model for predicting flow characteristics of Newtonian fluids in concentric horizontal annulus with drill pipe rotation is proposed. A numerical solution including pipe rotation is developed for calculating frictional pressure loss in concentric annuli for laminar and turbulent regimes. Navier-Stokes equations for turbulent conditions are numerically solved using the finite differences technique to obtain velocity profiles and frictional pressure losses. To verify the proposed model, estimated frictional pressure losses are compared with experimental data which were available in the literature and gathered at Middle East Technical University, Petroleum & Natural Gas Engineering Flow Loop (METU-PETE Flow Loop) as well as Computational Fluid Dynamics (CFD) software. The proposed model predicts frictional pressure losses with an error less than ± 10% in most cases, more accurately than the CFD software models depending on the flow conditions. Also, pipe rotation effects on frictional pressure loss and tangential velocity is investigated using CFD simulations for concentric and fully eccentric annulus. It has been observed that pipe rotation has no noticeable effects on frictional pressure loss for concentric annuli, but it significantly increases frictional pressure losses in an eccentric annulus, especially at low flow rates. For concentric annulus, pipe rotation improves the tangential velocity component, which does not depend on axial velocity. It is also noticed that, as the pipe rotation and axial velocity are increased, tangential velocity drastically increases for an eccentric annulus. The proposed model and the critical analysis conducted on velocity components and stress distributions make it possible to understand the concept of hydro transport and hole cleaning in field applications.

Pressure Losses and Limiting Reynolds Numbers for Non-Newtonian Fluids in Short Square-Edged Orifice Plates

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Butteur Ntamba Ntamba ◽  
Veruscha Fester
Keyword(s):  
Pressure Loss ◽  
Reynolds Numbers ◽  
Newtonian Fluids ◽  
Pressure Losses ◽  
Pressure Loss Coefficient ◽  
Stable Operating ◽  
Piping Systems ◽  
Laminar And Turbulent Flow ◽  
Loss Coefficients ◽  
Industrial Problem

Correlations predicting the pressure loss coefficient along with the laminar, transitional, and turbulent limiting Reynolds numbers with the β ratio are presented for short square-edged orifice plates. The knowledge of pressure losses across orifices is a very important industrial problem while predicting pressure losses in piping systems. Similarly, it is important to define stable operating regions for the application of a short orifice at lower Reynolds numbers. This work experimentally determined pressure loss coefficients for square-edged orifices for orifice-to-diameter ratios of β = 0.2, 0.3, 0.57, and 0.7 for Newtonian and non-Newtonian fluids in both laminar and turbulent flow regimes.

Determination of Full Range Stress-Strain Behavior of Pipeline Steels Using Tensile Characteristics

2010 ◽  
Author(s):  
Stijn Hertele´ ◽  
Wim De Waele ◽  
Rudi Denys
Keyword(s):  
Full Range ◽  
Tensile Tests ◽  
Proof Stress ◽  
Stress Strain ◽  
Pipeline Steels ◽  
Strain Behavior ◽  
Parameter Values ◽  
Near Future ◽  
Strain Model

It is standard practice to approximate the post-yield behavior of pipeline steels by means of the Ramberg-Osgood equation. However, the Ramberg-Osgood equation is often unable to accurately describe the stress-strain behavior of contemporary pipeline steels with a high Y/T ratio. This is due to the occurrence of two distinct, independent stages of strain hardening. To address this problem, the authors recently developed a new ‘UGent’ stress-strain model which provides a better description of those steels. This paper elaborates a methodology to estimate suited parameter values for the UGent model, starting from a set of tensile characteristics. Using the proposed methodology, good approximations have been obtained for a preliminary series of eight investigated stress-strain curves. Next to all common tensile characteristics, the 1% proof stress is needed. The authors therefore encourage the future acquisition of this stress level during tensile tests. Currently, the authors perform a further in-depth validation which will be reported in the near future.

Modelling of Shear Viscosity Behavior and Extrusion through Dies for Rubber Compounds

1987 ◽  
Vol 60 (2) ◽  
pp. 337-360 ◽  
Author(s):  
James L. White ◽  
Yeh Wang ◽  
Avraam I. Isayev ◽  
Nobuyuki Nakajima ◽  
Frederick C. Weissert ◽  
...  
Keyword(s):  
Cross Sections ◽  
Shear Viscosity ◽  
Flow Analysis ◽  
Elongational Flow ◽  
Extrudate Swell ◽  
Pressure Losses ◽  
Analysis And Design ◽  
Rubber Compounds ◽  
Viscosity Behavior ◽  
Active Research

Abstract This paper marks a first effort to develop a fundamental basis for die flow analysis and design for rubber compounds. We have accomplished a modelling of the shear viscosity function and its application to one- and two-dimensional shearing in die cross sections. There are major limitations in what we have done, much of which is apparent even in the early work of Mooney. In particular, we have not considered (i) slip phenomena on die walls, (ii) die entrance and exit pressure losses associated with converging and diverging dies, nor (iii) extrudate swell. We have an active research in our laboratories investigating these problems. In the future, we are seeking to generalize the procedures described in this paper to more complex die designs. Inclusion of entrance and exit effects and rigorous analysis of coathanger dies requires the handling of elongational flow contributions, a still unsolved problem.

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