scholarly journals Numerical study of surface tension effects on bubble detachment in a submerged needle

2015 ◽  
Author(s):  
J. Eshraghi ◽  
E. Kosari ◽  
P. Hadikhani ◽  
A. Amini ◽  
M. Ashjaee ◽  
...  
Keyword(s):  
Surface Tension ◽  
Numerical Study ◽  
Bubble Detachment

Investigation of Three-Dimensional Flow in Microchannels With Patterned Surfaces

2007 ◽  
Author(s):  
Auro Ashish Saha ◽  
Sushanta K. Mitra
Keyword(s):  
Surface Tension ◽  
Flow Instability ◽  
Numerical Study ◽  
Three Dimensional ◽  
Surface Characteristics ◽  
Bottom Wall ◽  
Surface Tension Effect ◽  
Hydrophobic Region ◽  
Side Walls ◽  
Dimensional Simulation

A three-dimensional numerical simulation of flow in patterned microchannel with alternate layers of hydrophilic and hydrophobic surfaces at the bottom wall is studied here. Surface characteristics of the microchannel are accounted by specifying the contact angle and the surface tension of the fluid. Meniscus profiles with varying amplitude and shapes are obtained under the different specified surface conditions. Flow instability increases as the fluid at the bottom wall traverses alternately from hydrophilic region to hydrophobic region. To understand the surface tension effect of the side walls, a two-dimensional numerical study has also been carried out for the microchannel and the results are compared with three-dimensional simulation. The surface tension effect of the side walls enhances the capillary effect for three-dimensional case.

Numerical Study of Microchamber Filling in Centrifugal Microfluidics

2011 ◽  
Author(s):  
Nick Niedbalski ◽  
Seok-Won Kang ◽  
Debjyoti Banerjee
Keyword(s):  
Surface Tension ◽  
Numerical Model ◽  
Physical Properties ◽  
Thermal Cycle ◽  
Numerical Study ◽  
Method Comparison ◽  
Thermal Conditions ◽  
Microfluidic System ◽  
Working Fluid ◽  
Driving Mechanism

Numerical investigation of the transient, coupled hydrodynamic and thermal behavior of a novel polymerase chain reaction (PCR) centrifugal microfluidic system is presented in this study. The driving mechanism for flow within these devices is modeled as a combination of the capillary forces and rotationally induced pressure gradient working in opposition to viscous forces, which are functions of rotation speed and fluid properties. The physical properties of the working fluid are in turn functions of temperature, some of which can have significant variations over the operating temperature ranges of a PCR thermal cycle. The complex balance of viscous, capillary, and rotationally induced inertial forces are crucial factors in optimizing the design of such devices. Hence, the effects of temperature variation on the filling performance cannot be neglected. A commercial CFD code is utilized to simulate the filling of a microchamber when subjected to thermal conditions typical of a PCR thermal cycle. The numerical model accounts for the temperature dependence of the working fluid’s viscosity and surface tension by simultaneously solving the Navier-Stokes and energy equations. The free surface morphology (position, shape) and total chamber fill fraction as a function of time is predicted by using the volume of fluids (VOF) method. Comparison of the predictions from the temperature dependent numerical model to that which assume said physical properties to be constant, demonstrates the strong effect of the fluid’s viscosity and surface tension on the filling rate for various rotation speeds.

NUMERICAL STUDY OF PATTERNS AND THEIR EVOLUTION IN FINITE GEOMETRIES

1996 ◽  
Vol 06 (10) ◽  
pp. 1883-1890 ◽  
Author(s):  
J. PONTES ◽  
C.I. CHRISTOV ◽  
M.G. VELARDE
Keyword(s):  
Surface Tension ◽  
Numerical Study ◽  
Surface Tension Gradient ◽  
Thermal Gradients ◽  
Finite Geometries ◽  
Relative Value ◽  
Finite Layer ◽  
Spatio Temporal ◽  
Buoyancy Driven Convection ◽  
Conductive State

Pattern formation in a finite layer of fluid induced either by buoyancy or by a surface-tension gradient is considered. The fluid is confined between poor conducting horizontal boundaries, leading to patterns with a characteristic horizontal scale much larger than the fluid depth. The evolution of the system is studied by numerical integration of the (1+2)D equation introduced by Knobloch [1990]: [Formula: see text] Here µ is the scaled bifurcation parameter, κ=1, and a represents the effects of a heat transfer finite Biot number. The coefficients β, δ and γ do not vanish when the boundary conditions at top and bottom are not identical (β≠0, δ≠0) or when non-Boussinesq effects are taken into account (γ≠0). When the conductive state becomes unstable due to surface-tension inhomogeneities, it is shown that the system evolves towards a stationary pattern of hexagons with up or down flow depending on the relative value of the coefficients β and δ. In the case of buoyancy-driven convection (β=δ≠0), the system displays a tesselation of steady squares. Knobloch’s equation also describes time-dependent patterns at high thermal gradients, including spatio-temporal chaos, due to the non-variational character of the equation.

Numerical Study and Scale Analysis of Inner and Outer Diameters Prediction in Fabrication of Hollow Fiber Membranes for Nerve Regeneration

2008 ◽  
Author(s):  
Jun Yin ◽  
Nicole Coutris ◽  
Yong Huang
Keyword(s):  
Surface Tension ◽  
Hollow Fiber ◽  
Numerical Study ◽  
Hollow Fiber Membrane ◽  
Nerve Repair ◽  
Vof Method ◽  
Fiber Spinning ◽  
Fabrication Process ◽  
Scale Analysis ◽  
And Control

Recently the semi-permeable hollow fiber membrane (HFM) is finding promising applications in promoting axonal outgrowth for nerve repair and regeneration. It is of interest to model the phase inversion-based HFM fabrication process and control the fabricated HFM geometry. The effect of gravity and surface tension which is frequently ignored in general fiber spinning should be carefully addressed in HFM fabrication modeling. Both the volume of fluid (VOF) method and the scale analysis have been applied to appreciate the effect of gravity and surface tension on the HFM geometry profile. The VOF method-based simulation results reveal that both the gravity and/or surface tension significantly reduce the predicted radii/diameters, while the scale analysis reveals that the gravity or surface tension affects the HFM fabrication process dynamics. Both the approaches warrant the need of including the gravity and surface tension in HFM fabrication process modeling.

Numerical Study on Impingement of a Droplet upon a Liquid Film

2010 ◽  
Vol 44-47 ◽  
pp. 2499-2503
Author(s):  
Hong Liu ◽  
Mao Zhao Xie ◽  
Su Chun Wang ◽  
Ming Jia
Keyword(s):  
Surface Tension ◽  
Liquid Film ◽  
Stokes Equations ◽  
Numerical Study ◽  
Surface Tension Force ◽  
Surface Force ◽  
Navier Stokes ◽  
Initial Kinetic Energy ◽  
Droplet Impingement ◽  
Fine Grid

This paper reports progress in the numerical simulations of a droplet impingement upon the wall film of the same liquid. The full Navier-Stokes equations are solved in axisymmetric formulation. The surface tension force is modeled by a continuum surface force (CSF) model. An adapting local refinement technique is used to provide the fine grid coupled by the volume-of fluid (VOF) method for tracking the interface between the gas and the droplet and liquid film. Results indicate that the motion behavior of droplet impingement upon the liquid film is dominantly influenced by the initial kinetic energy and the thickness of the film as well as the surface tension and the liquid viscosity.

The mechanism of bubble detachment from a wall at zero and negative gravity

1976 ◽  
Vol 77 (2) ◽  
pp. 313-320 ◽  
Author(s):  
G. Malcotsis
Keyword(s):  
Surface Tension ◽  
Vertical Wall ◽  
Two Dimensions ◽  
Gravity Force ◽  
Zero Gravity ◽  
Air Bubbles ◽  
Subcooled Boiling ◽  
Vapour Bubble ◽  
Approximate Representation ◽  
Bubble Detachment

An experiment has been carried out in which air bubbles were caused to grow isothermally at a vertical wall between two closely spaced horizontal plates. The experiment gives an approximate representation in two dimensions for the growth of a vapour bubble at a wall under some conditions of subcooled boiling in zero gravity. Although the effect of gravity was virtually eliminated in the experiment, it was found that a bubble could still detach itself from the wall, apparently owing to the effects of surface tension and inertia.Also, bubbles were seen to detach from a wall despite the presence of a slight gravity force directed to oppose such detachment.

Couette flow of two fluids between concentric cylinders

1985 ◽  
Vol 150 ◽  
pp. 381-394 ◽  
Author(s):  
Yuriko Renardy ◽  
Daniel D. Joseph
Keyword(s):  
Surface Tension ◽  
Viscous Fluid ◽  
Thin Layer ◽  
Couette Flow ◽  
Numerical Study ◽  
Outer Cylinder ◽  
Immiscible Fluids ◽  
Stable Configuration ◽  
Two Fluids ◽  
Concentric Cylinders

We consider the flow of two immiscible fluids lying between concentric cylinders when the outer cylinder is fixed and the inner one rotates. The interface is assumed to be concentric with the cylinders, and gravitational effects are neglected. We present a numerical study of the effect of different viscosities, different densities and surface tension on the linear stability of the Couette flow. Our results indicate that, with surface tension, a thin layer of the less-viscous fluid next to either cylinder is linearly stable and that it is possible to have stability with the less dense fluid lying outside. The stable configuration with the less-viscous fluid next to the inner cylinder is more stable than the one with the less-viscous fluid next to the outer cylinder. The onset of Taylor instability for one-fluid flow may be delayed by the addition of a thin layer of less-viscous fluid on the inner wall and promoted by a thin layer of more-viscous fluid on the inner wall.

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