The Determination of Wall Slip Velocity in the Laminar Gravity Flow of Non-Newtonian Fluids along Plane Surfaces

1974 ◽  
Vol 13 (4) ◽  
pp. 394-395 ◽  
Author(s):  
D. C.-H. Cheng
Keyword(s):  
Slip Velocity ◽  
Wall Slip ◽  
Newtonian Fluids ◽  
Gravity Flow

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.

Determination of the wall slip velocity in the flow of a SBR compound

1992 ◽  
Vol 31 (6) ◽  
pp. 565-574 ◽  
Author(s):  
Ph. Mourniac ◽  
J. F. Agassant ◽  
B. Vergnes
Keyword(s):  
Slip Velocity ◽  
Wall Slip

Study on Wall Slip in Pipeline Flow of Dense Paste

2014 ◽  
Vol 511-512 ◽  
pp. 50-54
Author(s):  
Fu Yan Lv ◽  
Zheng Meng Xia ◽  
Jie Gao ◽  
Xue Di Hao ◽  
Miao Wu
Keyword(s):  
Slip Velocity ◽  
Particle Concentration ◽  
Wall Slip ◽  
Test System ◽  
Pipe Diameter ◽  
Coal Slurry ◽  
Slip Mechanism ◽  
Apparent Slip ◽  
Slip Layer

The apparent wall slip flows of incompressible and viscoplastic fluids in plane pipeline were analyzed assuming that the apparent slip layer consists solely wall slip layershear layerslug flow part and they are independent of the flow rate. Taking coal slurry for example,the experiment is conducted on pressure pipe rheological and resistance characteristic test system. It studies how two key factors (the particle concentration and the pipe diameter) influence the dense paste wall slip velocity. The assumed apparent slip mechanism provides methodologies for the determination of the slip velocity values that are consistent with the traditional Mooney method and furthermore allows the determination of the true shear rate of the dense paste at the wall and the yield stress. The analysis of the slip data of various dense pastes of rigid particles reveals that the apparent slip layer thickness is related to the particle concentration and the pipe diameter.

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.

Determination of Phthalic Acid, 2-(3′,5′-Dibromo-2′,4′-Dihydroxybenzoyl) Benzoic Acid, and Tribromoresorcinol in the Color Additives D&C Red No. 21, D&C Red No. 22 (Eosin Y), and Their Lakes Using UHPLC

2019 ◽  
Vol 102 (3) ◽  
pp. 936-941 ◽  
Author(s):  
Nebebech Belai ◽  
Adrian Weisz
Keyword(s):  
Benzoic Acid ◽  
Phthalic Acid ◽  
Side Reaction ◽  
Gravity Flow ◽  
Eosin Y ◽  
Federal Regulations ◽  
Improved Method ◽  
Flow Method ◽  
By Products

Abstract Background: Certain impurities in the color additives drug and cosmetic (D&C) Red No. 21 (R21), D&C Red No. 22 (R22), and their lakes are limited to levels specified in the Code of Federal Regulations (CFR) and are quantified by the U.S. Food and Drug Administration in batches of these color additives submitted for certification. Currently, a lengthy and tedious method based on gravity flow elution column chromatography is used to quantify the following CFR-specified impurities: the intermediate, phthalic acid (PhthAc); the manufacturing by-products, 2-(3′,5′-dibromo-2′,4′-dihydroxybenzoyl)benzoic acid (Br2BBA); and brominated resorcinol. “Brominated resorcinol” implies the sum of all possible brominated resorcinols, but the current work focused on 2,4,6-tribromoresorcinol (Br3R) as the most probable side-reaction product. Objective: An improved method was needed to quantify PhthAc, Br2BBA, and Br3R in R21, R22, and their lakes. Methods: A rapid ultra-HPLC (UHPLC) method was developed to replace the gravity flow method for quantitative determination of PhthAc, Br2BBA, and Br3R. Results: PhthAc, Br2BBA, and Br3R were quantified by using five-point calibration curves with data point ranges of 0.11–1.55, 0.06–0.77, and 0.04–0.61% by weight, respectively. LODs for the analytes ranged from 0.01 to 0.03%. Recoveries of the analytes ranged from 90.6 to 99.9%. Conclusions: The UHPLC method is accurate and significantly more rapid than the gravity -flow method, requiring approximately 7 min as compared with 6 h to detect PhthAc, Br2BBA, and Br3R in one sample. Highlights: A rapid UHPLC method was developed to determine CFR-specified impurities in the color additives D&C Red Nos. 21 and 22 and their lakes.

Stokes flows of a Maxwell fluid with wall slip condition

2011 ◽  
Vol 89 (10) ◽  
pp. 1061-1071 ◽  
Author(s):  
Dumitru Vieru ◽  
Abdul Rauf
Keyword(s):  
Relative Velocity ◽  
Wall Slip ◽  
Maxwell Fluid ◽  
Approximate Solutions ◽  
Vortex Sheet ◽  
Exact Expression ◽  
Small Time ◽  
Newtonian Fluids ◽  
Slip Condition ◽  
Stokes Flows

Stokes flows of a Maxwell fluid produced by the motion of a wall are analyzed under the slip condition at the boundary. The wall is assumed to be translated in its plane with a given velocity. The relative velocity between the fluid at the wall and the wall is assumed to be proportional to the shear rate at the wall. The exact expressions for the velocity and shear stress are determined by means of a Laplace transform. The velocity fields corresponding to both slip and nonslip conditions for Maxwell and viscous Newtonian fluids are obtained. Two particular cases, namely sinusoidal oscillations and translation with a constant velocity of the wall, are studied. In the case of flows of a Maxwell fluid with a nonslip boundary condition, the velocity is discontinuous across a vortex sheet; this situation does not appear for flows with slip conditions. In this case, the velocity is always continuous. Because the exact expression for the velocity is rather complicated, two small-time and large-time expressions of the velocity are derived. Results for Maxwell fluids are compared with those of viscous Newtonian fluids in both cases of the flow with slip and nonslip conditions. Also, the exact and approximate solutions are compared and good agreement is found. In addition, the influence of the slip coefficient on the velocity and on the relative velocity is studied.

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.

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