Experimental Analysis and Flow Visualization of a Thin Liquid Film on a Stationary and Rotating Disk

1991 ◽  
Vol 113 (1) ◽  
pp. 73-80 ◽  
Author(s):  
S. Thomas ◽  
A. Faghri ◽  
W. Hankey
Keyword(s):  
Free Surface ◽  
Film Thickness ◽  
Liquid Film ◽  
Flow Visualization ◽  
Thin Liquid Film ◽  
Rotating Disk ◽  
Radial Spreading ◽  
Frictional Forces ◽  
The Mean ◽  
The Waves

The mean thickness of a thin liquid film of deionized water with a free surface on a stationary and rotating horizontal disk has been measured with a nonobtrusive capacitance technique. The measurements were taken when the rotational speed ranged from 0–300 rpm and the flow rate varied from 7.0–15.0 lpm. A flow visualization study of the thin film was also performed to determine the characteristics of the waves on the free surface. When the disk was stationary, a circular hydraulic jump was present on the disk. Upstream from the jump, the film thickness was determined by the inertial and frictional forces on the fluid, and the radial spreading of the film. The surface tension at the edge of the disk affected the film thickness downstream from the jump. For the rotating disk, the film thickness was dependent upon the inertial and frictional forces near the center of the disk and the centrifugal forces near the edge of the disk.

Marangoni instability of a thin liquid film heated from below by a local heat source

2003 ◽  
Vol 475 ◽  
pp. 377-408 ◽  
Author(s):  
SERAFIM KALLIADASIS ◽  
ALLA KIYASHKO ◽  
E. A. DEMEKHIN
Keyword(s):  
Free Surface ◽  
Liquid Film ◽  
Discrete Spectrum ◽  
Essential Spectrum ◽  
Marangoni Number ◽  
Thin Liquid Film ◽  
Nonlinear Partial Differential Equations ◽  
Spanwise Direction ◽  
Surface Boundary ◽  
Integral Boundary

We consider the motion of a liquid film falling down a heated planar substrate. Using the integral-boundary-layer approximation of the Navier–Stokes/energy equations and free-surface boundary conditions, it is shown that the problem is governed by two coupled nonlinear partial differential equations for the evolution of the local film height and temperature distribution in time and space. Two-dimensional steady-state solutions of these equations are reported for different values of the governing dimensionless groups. Our computations demonstrate that the free surface develops a bump in the region where the wall temperature gradient is positive. We analyse the linear stability of this bump with respect to disturbances in the spanwise direction. We show that the operator of the linearized system has both a discrete and an essential spectrum. The discrete spectrum bifurcates from resonance poles at certain values of the wavenumber for the disturbances in the transverse direction. The essential spectrum is always stable while part of the discrete spectrum becomes unstable for values of the Marangoni number larger than a critical value. Above this critical Marangoni number the growth rate curve as a function of wavenumber has a finite band of unstable modes which increases as the Marangoni number increases.

Measurement of Liquid Film Thickness for Annular Two-Phase HFC134a Gas-Liquid Ethanol Flow in the Vertical Tube

2021 ◽  
Author(s):  
Huacheng Zhang ◽  
Tutomo Hisano ◽  
Shoji Mori ◽  
Hiroyuki Yoshida
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Atmospheric Condition ◽  
Heating Surface ◽  
Operating Conditions ◽  
Liquid Film Thickness ◽  
Two Phase ◽  
Disturbance Waves ◽  
Analytical Approaches

Abstract Annular gas-liquid two-phase flows, such as the flows attached to the fuel rods of boiling water reactors (BWR), are a prevalent occurrence in industrial processes. At the gas-liquid interface of such flows, disturbance waves with diverse velocity and amplitude commonly arise. Since the thin liquid film between two successive disturbance waves leads to the dryout on the heating surface and limits the performance of the BWRs, complete knowledge of the disturbance waves is of great importance for the characterized properties of disturbance waves. The properties of disturbance waves have been studied by numerous researchers through extensive experimental and analytical approaches. However, most of the experimental data and analyses available in the literature are limited to the near atmospheric condition. In consideration of the properties of liquids and gases under atmospheric pressure which are distinct from those under BWR operating conditions (7 MPa, 285 °C), we employed the HFC134a gas and liquid ethanol whose properties at relatively low pressure and temperature (0.7 MPa, 40 °C) are similar to those of steam and water under BWR operating conditions as working fluids in a tubular test section having an inside diameter 5.0mm. Meanwhile, the liquid film thickness is measured by conductance probes. In this study, we report the liquid film thickness characteristics in a two-phase HFC134a gas-liquid ethanol flow. A simple model of the height of a disturbance wave was also proposed.

Surface instabilities of thin liquid film flow on a rotating disk

1999 ◽  
Vol 26 (1-2) ◽  
pp. 75-85 ◽  
Author(s):  
G. Leneweit ◽  
K. G. Roesner ◽  
R. Koehler
Keyword(s):  
Liquid Film ◽  
Film Flow ◽  
Thin Liquid Film ◽  
Rotating Disk ◽  
Liquid Film Flow

Three-dimensional surfactant-covered flows of thin liquid films on rotating cylinders

2018 ◽  
Vol 844 ◽  
pp. 61-91 ◽  
Author(s):  
Weihua Li ◽  
Satish Kumar
Keyword(s):  
Free Surface ◽  
Flow Visualization ◽  
Evolution Equations ◽  
Thin Liquid Film ◽  
Three Dimensional ◽  
Axial Direction ◽  
Liquid Films ◽  
Practical Applications ◽  
Rotation Rates ◽  
Visualization Experiments

The coating of discrete objects is an important but poorly understood step in the manufacturing of a broad variety of products. An important model problem is the flow of a thin liquid film on a rotating cylinder, where instabilities can arise and compromise coating uniformity. In this work, we use lubrication theory and flow visualization experiments to study the influence of surfactant on these flows. Two coupled evolution equations describing the variation of film thickness and concentration of insoluble surfactant as a function of time, the angular coordinate and the axial coordinate are solved numerically. The results show that surface-tension forces arising from both axial and angular variations in the angular curvature drive flows in the axial direction that tend to smooth out free-surface perturbations and lead to a stable speed window in which axial perturbations do not grow. The presence of surfactant leads to Marangoni stresses that can cause the stable speed window to disappear by driving flow that opposes the stabilizing flow. In addition, Marangoni stresses tend to reduce the spacing between droplets that form at low rotation rates, and reduce the growth rate of rings that form at high rotation rates. Flow visualization experiments yield observations that are qualitatively consistent with predictions from linear stability analysis and the simulation results. The visualizations also indicate that surfactants tend to suppress dripping, slow the development of free-surface perturbations, and reduce the shifting and merging of rings and droplets, allowing more time for solidifying coatings in practical applications.

Nonlinear Aspects of Subcritical Shallow-Water Flow Past Two-Dimensional Obstructions

1978 ◽  
Vol 22 (04) ◽  
pp. 203-211
Author(s):  
Nils Salvesen ◽  
C. von Kerczek
Keyword(s):  
Free Surface ◽  
Shallow Water ◽  
Flow Problem ◽  
Free Stream ◽  
The Body ◽  
Two Dimensional ◽  
Third Order ◽  
Submerged Body ◽  
The Mean ◽  
The Waves

Some nonlinear aspects of the two-dimensional problem of a submerged body moving with constant speed in otherwise undisturbed water of uniform depth are considered. It is shown that a theory of Benjamin which predicts a uniform rise of the free surface ahead of the body and the lowering of the mean level of the waves behind it agrees well with experimental data. The local steady-flow problem is solved by a numerical method which satisfies the exact free-surface conditions. Third-order perturbation formulas for the downstream free waves are also presented. It is found that in sufficiently shallow water, the wavelength increases with increasing disturbance strength for fixed values of the free-stream-Froude number. This is opposite to the deepwater case where the wavelength decreases with increasing disturbance strength.

Deformation characteristics of ultra-thin liquid film considering temperature and film thickness dependence of surface tension

2011 ◽  
Vol 17 (5-7) ◽  
pp. 983-990 ◽  
Author(s):  
Hiroshige Matsuoka ◽  
Koji Oka ◽  
Yusuke Yamashita ◽  
Fumihiro Saeki ◽  
Shigehisa Fukui
Keyword(s):  
Surface Tension ◽  
Film Thickness ◽  
Liquid Film ◽  
Thin Liquid Film ◽  
Thickness Dependence ◽  
Deformation Characteristics

Three-Dimensional Shear Driven Thin Liquid Film in a Duct

2006 ◽  
Author(s):  
H. Lan ◽  
M. Friedrich ◽  
B. F. Armaly ◽  
J. A. Drallmeier
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Flow Rate ◽  
High Speed ◽  
Volume Flow Rate ◽  
Incident Light ◽  
Thin Liquid Film ◽  
Air Flow ◽  
Three Dimensional ◽  
Vof Model

Measurements and predictions of three-dimensional shear driven thin liquid films by turbulent air flow in a duct are reported. FLUENT - CFD code is used to perform the numerical simulations and the Reynolds Averaged Navier-Stokes and continuity equations along with the Volume of Fluid (VOF) model and the realizable k-ε turbulence model are implemented for this task. Film thickness and width are reported as a function of air flow rate, liquid film volume flow rate and surface tension, and a comparison with preliminary measured results is made. The thickness of the shear driven liquid film is measured using an interferometric technique that makes use of the phase shift between the reflection of incident light from the top and bottom surfaces of the thin liquid film. The spatial resolution is determined based on the spot size of the incident light, which for the current configuration of the transmitting optics is approximately 10 microns. The resulting fringe pattern is imaged using a high-speed imaging camera operating at 2000 frames per second. The technique has proved successful in measuring thickness between 100 and 900 microns in these shear driven films. Simulation results reveal that higher gas flow velocity decreases the film thickness but increases its width, while higher liquid film flow rate increases the film thickness and increases its width. Reasonable comparison appears to exist between preliminary measured and simulated results.

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