Estimation of the wall slip velocity in the capillary flow of potato granule pastes

1995 ◽  
Vol 39 (1) ◽  
pp. 139-149 ◽  
Author(s):  
P. J. Halliday ◽  
A. C. Smith
Keyword(s):  
Slip Velocity ◽  
Capillary Flow ◽  
Wall Slip ◽  
Potato Granule

Evaluation of Slip Effects in the Capillary Flow of Foams

1999 ◽  
Vol 9 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Karim Bekkour
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Slip Velocity ◽  
Capillary Flow ◽  
Strong Dependence ◽  
Sodium Dodecyl ◽  
Wall Slip ◽  
Reynolds Analogy ◽  
Slip Effects ◽  
Wall Shear

Abstract Foams have been prepared from water added with a surfactant (Sodium-Dodecyl-Sulfate, SDS) and a polymer (Poly-Ethylene-Oxide, PEO) at different concentrations. This work was devoted to a study of the flow properties of the foams. The pressure drops were measured during flow in capillary tubes (2.5, 3.5 and 4 mm) in laminar regime. It was found a strong dependence of the flow curves on capillary diameter showing that pronounced wall slip effects exist. Two known approaches were applied to quantify the slip velocity: (a) the Mooney method, in which the key assumption is that the slip velocity depends only on the wall shear stress, was not applicable and (b) the Oldroyd-Jastrzebski method, in which the assumption is that the slip velocity depends not only on the wall shear stress but also on the flow geometry, yielded satisfactory results. The determination of the pressure drop coefficient showed that the Metzner and Reed correlation, i.e., the Reynolds analogy based on the generalised Reynolds number, could be applied if the data are corrected for slip effects.

Wall slip velocity measurement of molten polypropylene in capillary flow based on length-corrected Mooney technique

2016 ◽  
Vol 134 (11) ◽  
Author(s):  
Zhong Ren ◽  
Xingyuan Huang ◽  
Hesheng Liu
Keyword(s):  
Velocity Measurement ◽  
Slip Velocity ◽  
Capillary Flow ◽  
Wall Slip

scholarly journals Quantification of shear viscosity and wall slip velocity of highly concentrated suspensions with non-Newtonian matrices in pressure driven flows

2021 ◽  
Author(s):  
Patrick Wilms ◽  
Jan Wieringa ◽  
Theo Blijdenstein ◽  
Kees van Malssen ◽  
Reinhard Kohlus
Keyword(s):  
Shear Stress ◽  
Liquid Phase ◽  
Shear Rate ◽  
Shear Viscosity ◽  
Slip Velocity ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Wall Slip ◽  
Flow Index ◽  
Concentrated Suspensions

AbstractThe rheological characterization of concentrated suspensions is complicated by the heterogeneous nature of their flow. In this contribution, the shear viscosity and wall slip velocity are quantified for highly concentrated suspensions (solid volume fractions of 0.55–0.60, D4,3 ~ 5 µm). The shear viscosity was determined using a high-pressure capillary rheometer equipped with a 3D-printed die that has a grooved surface of the internal flow channel. The wall slip velocity was then calculated from the difference between the apparent shear rates through a rough and smooth die, at identical wall shear stress. The influence of liquid phase rheology on the wall slip velocity was investigated by using different thickeners, resulting in different degrees of shear rate dependency, i.e. the flow indices varied between 0.20 and 1.00. The wall slip velocity scaled with the flow index of the liquid phase at a solid volume fraction of 0.60 and showed increasingly large deviations with decreasing solid volume fraction. It is hypothesized that these deviations are related to shear-induced migration of solids and macromolecules due to the large shear stress and shear rate gradients.

Application of CFD-DSMC coupling method in micro-scale gas flow and combustion

2020 ◽  
Vol 34 (27) ◽  
pp. 2050301
Author(s):  
Shaoyi Suo ◽  
Linsong Jiang ◽  
Maozhao Xie
Keyword(s):  
Boundary Layer ◽  
Chemical Reaction ◽  
Wall Temperature ◽  
Slip Velocity ◽  
Gas Flow ◽  
Wall Slip ◽  
Reaction Products ◽  
Microscopic Method ◽  
Flow Heat ◽  
The Impact

The reversible elementary reaction mechanism of six components and seven steps of H2/O2 are applied by using a CFD-DSMC coupling iteration method to study the impact of boundary on flow, heat transfer and chemical reaction in a microtube. The microtube consists of a converging section and a straight section, which represents the gap on the contact surface of the pellets in porous media. It shows that after coupling, with the designed conditions in this paper, the influence of wall temperature is more obvious than that of wall slip velocity on the coupling results from the analysis of chemical reaction, yet the velocity field in the boundary layer is more affected by the wall slip velocity. In addition, the velocity in the central region of the flow decreases while the concentration of reaction products increases after coupling, due to the increasing of the velocity in the boundary layer and the influence of wall temperature, respectively. By the coupling of CFD-DSMC methods, more details and influence of the boundary can be considered, and the computational efficiency is higher than that of the single microscopic method.

Capillary Flow of Yield-Stress Fluids in Microchannels

2006 ◽  
Author(s):  
V. Bertola
Keyword(s):  
Yield Stress ◽  
Flow Regime ◽  
Capillary Flow ◽  
Capillary Tube ◽  
Plug Flow ◽  
Wall Slip ◽  
Critical Distance ◽  
Tube Diameter ◽  
Force Balance ◽  
Theoretical Argument

The wicking of a model yield-stress fluid (hair-gel solution in water) in a capillary tube is studied experimentally. By changing the hair-gel concentration in the solution, the yield stress varied from 5 to 20 Pa. A simple force balance between capillary and viscous forces suggests that the fluid should stop flowing as soon as the wall shear stress reaches the yield value, at a critical distance from the inlet which is independent of the tube diameter. However, this theoretical argument is not confirmed by experiments, which show that the fluid moves well beyond the critical distance determined theoretically, and that there is a well-defined effect of the tube diameter. It is proposed that such behavior may be determined by wall slip, which causes the flow to switch from the Poiseuille flow regime to the plug flow regime.

Periodical Pressure-Driven Flows in Microchannel with Wall Slip Velocity and Electro-Viscous Effects

2010 ◽  
Vol 22 (6) ◽  
pp. 829-837 ◽  
Author(s):  
Lei Wang ◽  
Jian-kang Wu
Keyword(s):  
Slip Velocity ◽  
Wall Slip ◽  
Viscous Effects ◽  
Pressure Driven

Melt fracture and wall slip of metallocene-catalyzed bimodal polyethylenes in capillary flow

2013 ◽  
Vol 57 (2) ◽  
pp. 393-406 ◽  
Author(s):  
Yong Woo Inn
Keyword(s):  
Capillary Flow ◽  
Wall Slip ◽  
Melt Fracture

Experimental study and molecular dynamics simulation of wall slip in a micro-extrusion flowing process

2011 ◽  
Vol 225 (5) ◽  
pp. 1175-1190 ◽  
Author(s):  
D Zhao ◽  
Y Jin ◽  
M Wang ◽  
M Song
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Molecular Dynamics Simulation ◽  
Slip Velocity ◽  
Polymer Melts ◽  
Critical Shear Stress ◽  
Wall Slip ◽  
Dynamics Simulation ◽  
Desorption Mechanism ◽  
Adsorption Desorption

Wall slip is one of the most important characteristics of polymer melts’ elasticity behaviours as well as the most significant factor which affects the flow of polymer melts. Based on the traditional Mooney method, through a double-barrel capillary rheometer, the relationship between velocities of wall slip, shear stress, shear rate, diameters of dies, and temperature of polypropylene (PP), high-density polyethylene (HDPE), polystyrene (PS), and polymethylmethacrylate (PMMA) is explored. The results indicate that the velocities of the wall slip of PP and HDPE increase apparently with shear stress and slightly with temperature. Meanwhile, the rise of temperature results in the decrease of critical shear stress. The wall-slip velocities of PS and PMMA are negative which means that the Mooney method based on the adsorption–desorption mechanism has determinate limitation to calculate the wall-slip velocity. Based on the entanglement–disentanglement mechanism, a new wall-slip model is built. With the new model, the calculation values of velocity of PP and HDPE correspond to the experimental values very well and the velocities of PS and PMMA are positive. The velocities of PS and PMMA increase obviously with the rise of shear stress. The rise of temperature results in the increase of velocity and decrease of critical shear stress. Then, the molecular dynamics simulation is used to investigate the combining energy between four polymer melts and the inside wall. The results show that at the given temperature and pressure, the molecules of PS and PMMA combine with atoms of the wall more tightly than those of PP and HDPE which means when wall slip occurs, the molecules of PS and PMMA near the wall will adsorb to the surface of the wall. However, those of PP and HDPE will be easy to slip. Therefore, the wall-slip mechanism of PP and HDPE is the adsorption–desorption mechanism, and that of PS and PMMA is the entanglement–disentanglement mechanism. According to the different wall-slip mechanisms of four polymers, an all-sided calculation method of wall-slip velocity is raised which consummates the theory of wall slip of polymer melts.

Development Length in Planar Channel Flows of Newtonian Fluids Under the Influence of Wall Slip

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
L. L. Ferrás ◽  
A. M. Afonso ◽  
M. A. Alves ◽  
J. M. Nóbrega ◽  
F. T. Pinho
Keyword(s):  
Slip Velocity ◽  
Numerical Study ◽  
Fluid Flows ◽  
Wall Slip ◽  
Newtonian Fluids ◽  
Planar Channel ◽  
Development Length ◽  
Navier Slip ◽  
Slip Boundary ◽  
Low Reynolds Number Flows

This technical brief presents a numerical study regarding the required development length (L=Lfd/H) to reach fully developed flow conditions at the entrance of a planar channel for Newtonian fluids under the influence of slip boundary conditions. The linear Navier slip law is used with the dimensionless slip coefficient k¯l=kl(μ/H), varying in the range 0<k¯l≤1. The simulations were carried out for low Reynolds number flows in the range 0<Re≤100, making use of a rigorous mesh refinement with an accuracy error below 1%. The development length is found to be a nonmonotonic function of the slip velocity coefficient, increasing up to k¯l≈0.1-0.4 (depending on Re) and decreasing for higher k¯l. We present a new nonlinear relationship between L, Re, and k¯l that can accurately predict the development length for Newtonian fluid flows with slip velocity at the wall for Re of up to 100 and k¯l up to 1.

Wall slip in the capillary flow of molten polymers subject to viscous heating

AIChE Journal ◽  
1997 ◽  
Vol 43 (3) ◽  
pp. 598-608 ◽  
Author(s):  
Eugene E. Rosenbaum ◽  
Savvas G. Hatzikiriakos
Keyword(s):  
Capillary Flow ◽  
Wall Slip ◽  
Viscous Heating ◽  
Molten Polymers
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