Fluorescent imaging system for global measurement of liquid film thickness and dynamic contact angle in free surface flows

1997 ◽  
Vol 68 (11) ◽  
pp. 4097-4102 ◽  
Author(s):  
M. F. G. Johnson ◽  
R. A. Schluter ◽  
S. G. Bankoff
Keyword(s):  
Contact Angle ◽  
Free Surface ◽  
Film Thickness ◽  
Liquid Film ◽  
Imaging System ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Free Surface Flows ◽  
Fluorescent Imaging ◽  
Surface Flows

The Pressure Drop and Dynamic Contact Angle of Motion of Triple-Lines in Hydrophobic Microchannels

2010 ◽  
Author(s):  
Dongin Yu ◽  
Chiwoong Choi ◽  
Moohwan Kim
Keyword(s):  
Contact Angle ◽  
Pressure Drop ◽  
Liquid Film ◽  
Dynamic Contact Angle ◽  
Triple Line ◽  
Dynamic Contact ◽  
Superficial Velocity ◽  
Channel Diameter ◽  
Fluid Property ◽  
Static Contact

At two-phase flow in microchannels, slug flow regime is different for wettability of surface. A slug in a hydrophilic microchannel has liquid film. However, a slug in a hydrophobic microchannel has no liquid film instead, the slug has triple-lines and makes higher pressure drop due to the motion of the triple-line. In previous researches, pressure drop of triple-line is depended of dynamic contact angle, channel diameter and fluid property. And, dynamic contact angle is depended of static contact angle, superficial velocity and fluid property. In order to understand the pressure drop of motion of triple-lines, pressure drop of slug with triple-lines in case of various diameters (0.546, 0.763, 1.018, 1.555, 2.075 mm), various fluids (D.I.water, D.I.water-1, 5, 10% ethanol mixture) and various superficial velocity (j = 0.01∼0.4 m/s) was measured. Dynamic contact angle was calculated from relation of the pressure drop of slug with triple-lines. Comparing with previous dynamic contact angle correlations, previous correlation underestimated dynamic contact angle in the region of this study. (10−4≤Ca≤10−3, 10−2≤We≤10−1, 68°≤θS≤110°)

A Numerical Investigation of the Free Surface Flow During Optical Fiber Coating Process

2001 ◽  
Author(s):  
C. S. L. Liu ◽  
S. H.-K. Lee
Keyword(s):  
Contact Angle ◽  
Free Surface ◽  
Optical Fiber ◽  
Dynamic Contact Angle ◽  
Air Entrainment ◽  
Dynamic Contact ◽  
Coating Process ◽  
Coating Quality ◽  
Fiber Coating ◽  
Drawing Speed

Abstract Optical fiber has increasingly played a crucial role in the information transmission area nowadays. The elevated demand makes it necessary to manufacture high quality light-guide fibers that have proper mechanical properties to endure the stresses induced during installations and operations. Optical fiber coating process provides a protection layer to shield the fiber from surface abrasion and also to increase the fiber’s tensile strength. However, there are problems encountered during this process which reduce the coating quality. One of the major problems is air entrainment, which may lead to eccentrical or incomplete coating. Apparently, it is of great interest to study this problem to improve the coating quality. Many experimental studies have been performed on the dynamic contact angle, air entrainment velocity and their correlation with various parameters, such as the viscosity and the surface tension of coating materials, fiber drawing speed, etc. Nevertheless, how the coating flow affects the upper meniscus (directly related with dynamic contact angle and air entrainment) has not been intensively studied. Understanding of the effects is essential to improve the coating quality. To fulfill this requirement, the present work focused on investigating the relation of upper meniscus and fiber drawing speed. This is just the first part of the serial study on the optical fiber coating process. Firstly, a numerical code was developed with finite volume formulation. The results showed that the code had the capacity to deal with this free surface fluid flow problem. The simulated free surface shape was validated with experimental data available. The trend of the upper meniscus shape and dynamic contact angle developments at high drawing velocity was simulated. The results showed, as expected, that the dynamic contact angle would approach 180° with the increase of the fiber-drawing speed.

scholarly journals Spreading Kinetics of Herschel-Bulkley Fluids Over Solid Substrates

2020 ◽  
Vol 8 ◽  
Author(s):  
Jie Zhang ◽  
Hai Gu ◽  
Jianhua Sun ◽  
Bin Li ◽  
Jie Jiang ◽  
...  
Keyword(s):  
Contact Angle ◽  
Film Thickness ◽  
Yield Stress ◽  
Power Law ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Yield Behavior ◽  
Yield Zone ◽  
Solid Substrates ◽  
Kinetics Of

The spreading kinetics of Herschel-Bulkley fluids on horizontal solid substrates were theoretically studied. The equations of film thickness were derived in both gravitational and capillary regimes. The dynamic contact angle for the capillary regime was also derived. Finally, a limiting result for the case of τ0 = 0 was obtained, which was compared with the known solution for validation. The results show that the yield behavior of the fluids had a significant impact on the spreading kinetics in both cases. Only when stress was larger than the yield stress, would substantial flow occur. The spreading zone was divided into two parts by the yield surface: sheared zone and yield zone, which was completely different from common Newtonian fluids or power-law fluids. The thickness of the yield zone mainly depended on yield stress and pressure gradient along the z-direction. According to the final evolution, both the film thickness and dynamic contact angle were affected not only by the power-law index but also by the yield behavior.

Investigation of behavior of the dynamic contact angle in a problem of convective flows

2017 ◽  
Vol 5 (4) ◽  
pp. 27-42
Author(s):  
O.N Goncharova ◽  
◽  
I.V. Marchuk ◽  
A.V. Zakurdaeva ◽  
◽  
...  
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Convective Flows

scholarly journals Viscous free-surface flows past cylinders

2020 ◽  
Vol 5 (8) ◽  
Author(s):  
Edward M. Hinton ◽  
Andrew J. Hogg ◽  
Herbert E. Huppert
Keyword(s):  
Free Surface ◽  
Free Surface Flows ◽  
Surface Flows
Sign in / Sign up

Export Citation Format

Share Document