Slip velocity over a perforated or patchy surface

2010 ◽  
Vol 643 ◽  
pp. 471-477 ◽  
Author(s):  
C. POZRIKIDIS
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Solid Fraction ◽  
Solid Surface ◽  
Slip Velocity ◽  
Functional Dependence ◽  
Numerical Results ◽  
Surface Geometry ◽  
Universal Law

Shear flow over a solid surface containing perforations or patches of zero shear stress is discussed with a view to evaluating the slip velocity. In both cases, the functional dependence of the slip velocity on the solid fraction of the surface strongly depends on the surface geometry, and a universal law cannot be established. Numerical results for flow over a plate with circular or square perforations or patches of zero shear stress, and flow over a plate consisting of separated square or circular tiles corroborate the assertion.

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.

Tracings of Behavior of Myoblasts Cultured Under Couette Type of Shear Flow Between Parallel Disks

2021 ◽  
Author(s):  
Shigehiro Hashimoto ◽  
Hiroki Yonezawa
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Rotating Disk ◽  
Time Lapse ◽  
Mechanical Stimuli ◽  
Parallel Disks ◽  
Before And After ◽  
A Cell

Abstract A cell deforms and migrates on the scaffold under mechanical stimuli in vivo. In this study, a cell with division during shear stress stimulation has been observed in vitro. Before and after division, both migration and deformation of each cell were analyzed. To make a Couette-type shear flow, the medium was sandwiched between parallel disks (the lower stationary culture-disc and the upper rotating disk) with a constant gap. The wall shear stress (1.5 Pa < τ < 2 Pa) on the surface of the lower culture plate was controlled by the rotational speed of the upper disc. Myoblasts (C2C12: mouse myoblast cell line) were used in the test. After cultivation without flow for 24 hours for adhesion of the cells to the lower disk, constant τ was applied to the cells in the incubator for 7 days. The behavior of each cell during shear was tracked by time-lapse images observed by an inverted phase contrast microscope placed in the incubator. Experimental results show that each cell tends to divide after higher activities: deformation and migration. The tendency is remarkable at the shear stress of 1.5 Pa.

scholarly journals The lift on a small sphere in a slow shear flow

1965 ◽  
Vol 22 (2) ◽  
pp. 385-400 ◽  
Author(s):  
P. G. Saffman
Keyword(s):  
Shear Flow ◽  
Velocity Profile ◽  
Kinematic Viscosity ◽  
Lift Force ◽  
Flow Direction ◽  
Functional Dependence ◽  
Small Sphere ◽  
Translation Velocity ◽  
Parabolic Velocity Profile ◽  
Direction Opposite

It is shown that a sphere moving through a very viscous liquid with velocity V relative to a uniform simple shear, the translation velocity being parallel to the streamlines and measured relative to the streamline through the centre, experiences a lift force 81·2μVa2k½/v½ + smaller terms perpendicular to the flow direction, which acts to deflect the particle towards the streamlines moving in the direction opposite to V. Here, a denotes the radius of the sphere, κ the magnitude of the velocity gradient, and μ and v the viscosity and kinematic viscosity, respectively. The relevance of the result to the observations by Segrée & Silberberg (1962) of small spheres in Poiseuille flow is discussed briefly. Comments are also made about the problem of a sphere in a parabolic velocity profile and the functional dependence of the lift upon the parameters is obtained.

Modelling a surfactant-covered droplet on a solid surface in three-dimensional shear flow

2020 ◽  
Vol 897 ◽  
Author(s):  
Haihu Liu ◽  
Jinggang Zhang ◽  
Yan Ba ◽  
Ningning Wang ◽  
Lei Wu
Keyword(s):  
Shear Flow ◽  
Solid Surface ◽  
Three Dimensional ◽  
Image Position

The Reynolds Analogy Applied to a Cylinder Rotating in Air

1954 ◽  
Vol 58 (519) ◽  
pp. 205-208 ◽  
Author(s):  
Y. R. Mayhew
Keyword(s):  
Heat Transfer ◽  
Shear Stress ◽  
Heat Flow ◽  
Solid Surface ◽  
Fluid Flows ◽  
Flat Plates ◽  
Reynolds Analogy ◽  
Transfer Data ◽  
Turbulent Fluid ◽  
Flow Through

When a turbulent fluid flows past a solid surface whose temperature differs from that of the fluid, the shear stress at the surface and the heat flow from it can be related by means of the Reynolds analogy. This analogy has been improved by Prandtl, Taylor, von Kármán and others, and its validity has been tested for flow through tubes and past flat plates by several investigators. In this note the analogy is checked against shear stress data and heat transfer data for a cylinder rotating in “still” air, when the flow is turbulent.

Responses of human adipose-derived stem cells to interstitial level of extremely low shear flows regarding differentiation, morphology, and proliferation

Lab on a Chip ◽  
2017 ◽  
Vol 17 (12) ◽  
pp. 2115-2124 ◽  
Author(s):  
Sung-Hwan Kim ◽  
Kihoon Ahn ◽  
Joong Yull Park
Keyword(s):  
Stem Cells ◽  
Shear Stress ◽  
Shear Flow ◽  
Shear Flows ◽  
Stress Gradient ◽  
Adipose Derived Stem Cells ◽  
Shear Stress Gradient ◽  
Low Shear

We developed a shear stress-gradient chip, which mimickedin vivointerstitial level of flow. With this system, hASCs' quantitative responses to the interstitial level of shear flow are identified.

Slip length for longitudinal shear flow over an arbitrary-protrusion-angle bubble mattress: the small-solid-fraction singularity

2017 ◽  
Vol 820 ◽  
pp. 580-603 ◽  
Author(s):  
Ory Schnitzer
Keyword(s):  
Shear Flow ◽  
Asymptotic Analysis ◽  
Solid Fraction ◽  
Asymptotic Expansions ◽  
Slip Length ◽  
Longitudinal Shear ◽  
Unidirectional Flow ◽  
Effective Slip Length ◽  
Effective Slip ◽  
Scaling Arguments

We study the effective slip length for unidirectional flow over a superhydrophobic mattress of bubbles in the small-solid-fraction limit $\unicode[STIX]{x1D716}\ll 1$. Using scaling arguments and utilising an ideal-flow analogy we elucidate the singularity of the slip length as $\unicode[STIX]{x1D716}\rightarrow 0$: relative to the periodicity it scales as $\log (1/\unicode[STIX]{x1D716})$ for protrusion angles $0\leqslant \unicode[STIX]{x1D6FC}<\unicode[STIX]{x03C0}/2$ and as $\unicode[STIX]{x1D716}^{-1/2}$ for $0<\unicode[STIX]{x03C0}/2-\unicode[STIX]{x1D6FC}=O(\unicode[STIX]{x1D716}^{1/2})$. We continue with a detailed asymptotic analysis using the method of matched asymptotic expansions, where ‘inner’ solutions valid close to the solid segments are matched with ‘outer’ solutions valid on the scale of the periodicity, where the bubbles protruding from the solid grooves appear to touch. The analysis yields asymptotic expansions for the effective slip length in each of the protrusion-angle regimes. These expansions overlap for intermediate protrusion angles, which allows us to form a uniformly valid approximation for arbitrary protrusion angles $0\leqslant \unicode[STIX]{x1D6FC}\leqslant \unicode[STIX]{x03C0}/2$. We thereby explicitly describe the transition with increasing protrusion angle from a logarithmic to an algebraic small-solid-fraction slip-length singularity.

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