scholarly journals Nonisothermal creeping flow of viscoelastic fluid with free surface during forming fibers

2010 ◽  
pp. 101-108
Author(s):  
B.A. Snigerev ◽  
◽  
F.Kh. Tazyukov ◽  
Keyword(s):  
Free Surface ◽  
Viscoelastic Fluid ◽  
Creeping Flow

An implicit scheme for simulation of free surface non-Newtonian fluid flows on dynamically adapted grids

2021 ◽  
Vol 36 (3) ◽  
pp. 165-176
Author(s):  
Kirill Nikitin ◽  
Yuri Vassilevski ◽  
Ruslan Yanbarisov
Keyword(s):  
Free Surface ◽  
Numerical Model ◽  
Newtonian Fluid ◽  
Viscoelastic Fluid ◽  
Fluid Flows ◽  
Numerical Results ◽  
Implicit Scheme ◽  
New Approach

Abstract This work presents a new approach to modelling of free surface non-Newtonian (viscoplastic or viscoelastic) fluid flows on dynamically adapted octree grids. The numerical model is based on the implicit formulation and the staggered location of governing variables. We verify our model by comparing simulations with experimental and numerical results known from the literature.

On the velocity discontinuity at a critical volume of a bubble rising in a viscoelastic fluid

2016 ◽  
Vol 789 ◽  
pp. 310-346 ◽  
Author(s):  
D. Fraggedakis ◽  
M. Pavlidis ◽  
Y. Dimakopoulos ◽  
J. Tsamopoulos
Keyword(s):  
Viscoelastic Fluid ◽  
Stationary Solutions ◽  
Creeping Flow ◽  
Experimental Results ◽  
Critical Volume ◽  
Rise Velocity ◽  
Abrupt Increase ◽  
Bubble Volume ◽  
Velocity Discontinuity ◽  
Velocity Jump

We examine the abrupt increase in the rise velocity of an isolated bubble in a viscoelastic fluid occurring at a critical value of its volume, under creeping flow conditions. This ‘velocity discontinuity’, in most experiments involving shear-thinning fluids, has been somehow associated with the change of the shape of the bubble to an inverted teardrop with a tip at its pole and/or the formation of the ‘negative wake’ structure behind it. The interconnection of these phenomena is not fully understood yet, making the mechanism of the ‘velocity jump’ unclear. By means of steady-state analysis, we study the impact of the increase of bubble volume on its steady rise velocity and, with the aid of pseudo arclength continuation, we are able to predict the stationary solutions, even lying in the discontinuous area in the diagrams of velocity versus bubble volume. The critical area of missing experimental results is attributed to a hysteresis loop. The use of a boundary-fitted finite element mesh and the open-boundary condition are essential for, respectively, the correct prediction of the sharply deformed bubble shapes caused by the large extensional stresses at the rear pole of the bubble and the accurate application of boundary conditions far from the bubble. The change of shape of the rear pole into a tip favours the formation of an intense shear layer, which facilitates the bubble translation. At a critical volume, the shear strain developed at the front region of the bubble sharply decreases the shear viscosity. This change results in a decrease of the resistance to fluid displacement, allowing the developed shear stresses to act more effectively on bubble motion. These coupled effects are the reason for the abrupt increase of the rise velocity. The flow field for stationary solutions after the velocity jump changes drastically and intense recirculation downstream of the bubble is developed. Our predictions are in quantitative agreement with published experimental results by Pilz & Brenn (J. Non-Newtonian Fluid Mech., vol. 145, 2007, pp. 124–138) on the velocity jump in fluids with well-characterized rheology. Additionally, we predict shapes of larger bubbles when both inertia and elasticity are present and obtain qualitative agreement with experiments by Astarita & Apuzzo (AIChE J., vol. 11, 1965, pp. 815–820).

scholarly journals Stress Distribution in Creeping Flow of a Viscoelastic Fluid around a Single Bubble

1987 ◽  
Vol 15 (3) ◽  
pp. 147-152
Author(s):  
Kazumori FUNATSU ◽  
Toshihisa KAJIWARA ◽  
Yukihiro SHIRAISHI ◽  
Hiroshi MATSUO
Keyword(s):  
Stress Distribution ◽  
Viscoelastic Fluid ◽  
Creeping Flow ◽  
Single Bubble

Creeping flow analyses of free surface cavity flows

1996 ◽  
Vol 8 (6) ◽  
pp. 415-433 ◽  
Author(s):  
P. H. Gaskell ◽  
J. L. Summers ◽  
H. M. Thompson ◽  
M. D. Savage
Keyword(s):  
Free Surface ◽  
Creeping Flow ◽  
Cavity Flows ◽  
Surface Cavity

Stability of Hadley Circulations in a Viscoelastic Fluid With Deformable Free Surface

2003 ◽  
Author(s):  
P. N. Kaloni ◽  
J. X. Lou
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Stability Analysis ◽  
Eigenvalue Problem ◽  
Viscoelastic Fluid ◽  
Lower Surface ◽  
Horizontal Layer ◽  
Convective Stability ◽  
Rigid Plate ◽  
Temperature Dependent

This paper deals with liner convective stability analysis of Oldroyd B fluid in a thin horizontal layer with a deformable free surface. The lower surface of the layer is in contact with an adiabatic rigid plate and the upper deformable surface is subject to a temperature dependent surface tension. The eigenvalue problem is solved by the Chebyshev Tau-QZ method and the results for various different forms of upper surfaces are presented.

Extrusion of Polymer Melts and Melt Flow Instabilities. III. Theoretical Analysis of Extrusion through a Slit Die

1969 ◽  
Vol 42 (3) ◽  
pp. 691-699 ◽  
Author(s):  
James L. White
Keyword(s):  
Reynolds Number ◽  
Stress Field ◽  
Viscoelastic Fluid ◽  
Polymer Melts ◽  
Second Order ◽  
Secondary Flows ◽  
Newtonian Fluids ◽  
Creeping Flow ◽  
Flow Instabilities ◽  
Field Problem

Abstract In the previous sections of this paper we have discussed our own and other experimental studies of flow instabilities in the extrusion of polymer melts as well as various theories of the mechanism of initiation of the instability. It is our belief that one of the keys to a deeper understanding of this phenomenon is a fuller analytical understanding of the stress and velocity fields in the composite reservoir, capillary, and extrudate system. It is to this problem that we turn our attention here. The velocity, stress-field problem in the entrance region of a conduit being fed from a reservoir has received considerable attention for Newtonian fluids. Most authors have followed Schlichting and Goldstein in using boundary-layer theory to analyze this problem. While there are a number of such solutions for viscous non-Newtonian and viscoelastic fluids, they are of little interest for polymer melts. This is not only because they represent a high Reynolds number, inertia-dominated asymptote but because they neglect all phenomena occurring in the reservoir feeding the conduit. Of more interest are the low Reynolds number creeping flow solutions for Newtonian fluids which are based upon the work of Sampson (see also Roscoe and Weissberg). A decade ago Tomita published a pioneering analysis of the creeping flow of a viscous non-Newtonian (power-law) fluid into a sharp edge entrance of a capillary. More recently LaNieve and Bogue have analyzed the creeping flow of a Coleman-Noll second order into the capillary entrance. A recent study of the entry problem has been made by Metzner, Uebler, and Chan Man Fong. The related problem of creeping flow of a viscoelastic fluid in a converging channel or cone has been analyzed by Adams, Whitehead, and Bogue and Kaloni. While the former authors computed the stress field for a second-order fluid and an integral constitutive equation in a presumed velocity field, Kaloni actually evaluated velocity profiles and predicted the formation of secondary flows. A more intuitive, but far less rigorous approach to extrusion of a viscoelastic fluid has been taken by Dexter and Dienes and Smith. These authors presume a virgin material to enter a capillary die in fully developed flow and utilize the theory of linear viscoelasticity to evaluate the stress field.

Sign in / Sign up

Export Citation Format

Share Document