Formation of a secondary droplet over the crown upon the liquid film rupture under the action of a laser beam

2016 ◽  
Vol 51 (1) ◽  
pp. 99-108
Author(s):  
A. S. Ovcharova
Keyword(s):  
Laser Beam ◽  
Liquid Film ◽  
Secondary Droplet ◽  
Film Rupture

Dynamics of liquid film rupture under local heating

2022 ◽  
Vol 184 ◽  
pp. 122376
Author(s):  
D. Zaitsev ◽  
D. Kochkin ◽  
O. Kabov
Keyword(s):  
Liquid Film ◽  
Local Heating ◽  
Film Rupture

An Experimental Study on Liquid Film Dynamics and Interfacial Wave of Air-Water Two-Phase Flow in a Horizontal Channel

2013 ◽  
Author(s):  
Youjia Zhang ◽  
Weimin Ma ◽  
Shengjie Gong
Keyword(s):  
Liquid Film ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Research Work ◽  
Water Film ◽  
Test Facility ◽  
Phase Flow ◽  
Interfacial Wave ◽  
Film Rupture ◽  
Two Phase

This study is concerned with liquid film dynamics and stability of annular flow, which plays an important role in understanding film rupture and dryout in boiling heat transfer. The research work starts from designing and making a test facility which enables the visualization and measurement of liquid film dynamics. A confocal optical sensor is applied to track the evolution of film thickness. A horizontal rectangular channel made of glass is used as the test section. Deionized water and air are supplied into that channel in such a way that an initial stratified flow forms, with the liquid film on the bottom wall. The present study is focused on characterization of liquid film profile and dynamics in term of interfacial wave and shear force induced film rupture under adiabatic condition. Based on the experimental data and analysis, it is found that given a constant water flowrate, the average thickness of water film decreases with increasing air flowrate, while the interfacial wave of the two-phase flow is intensified. As the air flowrate reaches a critical value, a localized rupture of the water film occurs.

Instantaneous Optical Measurement of the Temperature at the Interface Between a Wall and a Thin Liquid Film

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Brian E. Fehring ◽  
Roman W. Morse ◽  
Jason Chan ◽  
Kristofer M. Dressler ◽  
Evan T. Hurlburt ◽  
...  
Keyword(s):  
Laser Beam ◽  
Liquid Film ◽  
Solid Wall ◽  
Incident Angle ◽  
Thin Liquid Film ◽  
Index Of Refraction ◽  
High Temporal Resolution ◽  
Flow Measurements ◽  
Vapor Interface ◽  
Liquid Vapor

Abstract Instantaneous temperature measurements at the interface between a solid wall and a thin, unsteady liquid film are performed using thermoreflectance, a nonintrusive optical technique with high temporal resolution. A laser beam is directed at a wall–liquid interface, and the intensity of the light reflected at that interface is measured by a photodiode. The intensity of the reflected light varies with the index of refraction of the liquid at the wall. The index of refraction is a function of temperature, which enables the instantaneous measurement of the wall temperature. In the presence of thin liquid films, reflections from the liquid–vapor interface at the free surface of the film generate noise in the measurements. We demonstrate that orienting the laser beam at a large incident angle, close to total internal reflection, minimizes noise from the liquid–vapor interface while increasing the sensitivity of the measurement. The thermoreflectance technique is validated in an unsteady two-phase annular flow. Measurements of temperature fluctuations less than 1 K in amplitude are achieved, with an uncertainty of 0.1 K.

Study on Breakdown Features and Characteristics of Film at the Corrugated Plate Corner

2020 ◽  
Author(s):  
Bo Wang ◽  
Bowen Chen ◽  
Bingzheng Ke ◽  
Ru Li ◽  
Gongqing Wang ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Film Thickness ◽  
Liquid Film ◽  
Relative Position ◽  
Water Film ◽  
Theoretical Formula ◽  
Film Rupture ◽  
Water Separation ◽  
Water Film Thickness ◽  
Film Breakdown

Abstract Corrugated plate dryer is a extremely vital equipment for steam-water separation in the fields of heat transfer and nuclear engineering. The corrugated plate is also a commonly used steam-water separator in steam generators in nuclear power plants. It is meaningful to study the breakdown characteristics and mechanism of the water film on corrugated plate wall. Water film thickness of steady flow is measured based on plane laser induced fluorescence (PLIF) technique and time series and its fitted equation of water film thickness are obtained, respectively. Besides, fluctuation characteristics of water film are analyzed by probability density function (PDF). Based on the dimensionless approach, the water film breakdown model at the corner of the corrugated plate is established. And the calculation equation of the relative position of the water film breakdown at the corner is deprived. The specific conclusions are as follows. The theoretical equation agrees well with the relative position of the water film breakdown at the corrugated plate corner. The evolution of the surface wave of water film is carried out in time and space. The PDF curve have no significant peak characteristics. Therefore, the spectrum has no characteristic frequency, that is, the water film has multi-frequency characteristics. Gravity of water film can be ignored in the water film model. The thickness sequences for falling film is measured and fitted. The two-dimensional model of water film breakdown at the corner is set up. The equation for the film thickness when the water film is just ruptured is obtained. Relative position of the water film rupture at the corner of the corrugated plate is theoretically related only to the structural parameters of the corrugated plate, the parameters of the gas phase and the liquid phase, and the Reynolds number of the liquid film. However, in the low Reynolds number region, the airflow velocity is extremely large, which causes certain fluctuations and nonlinear characteristics of the water film boundary position. Therefore, the theoretical formula is not particularly good at predicting the relative position of the breakdown in this region. I think that this nonlinear feature has obvious chaotic characteristics. The study of the chaotic characteristics generated by shearing the liquid film by high velocity flow airflow at the corner of the corrugated plate may become a prospect for future research.

scholarly journals Термокапиллярные структуры и разрыв нагреваемой пленки жидкости

2019 ◽  
Vol 45 (14) ◽  
pp. 44
Author(s):  
Е.А. Чиннов
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Liquid Film ◽  
Critical Heat Flux ◽  
Type A ◽  
Vertical Surface ◽  
Film Rupture ◽  
Interaction Of Waves

The data of thermocapillary structures formation and breakdown of the heated liquid film flowing down on a vertical surface with the Reynolds number varied from 0.1 up to 500 are analyzed. It is shown that the interaction of waves with thermocapillary structures type A leads to an increase in critical heat flux, corresponding to the liquid film rupture, compared with literature data (regime B).

Nonlinear Rupture of Thin Micropolar Liquid Film Under a Magnetic Field

2016 ◽  
Vol 33 (2) ◽  
pp. 249-256
Author(s):  
P.-J. Cheng ◽  
C.-K. Chen ◽  
Y.-C. Wang ◽  
M.-C. Lin ◽  
C.-K. Yang
Keyword(s):  
Magnetic Field ◽  
Liquid Film ◽  
Evolution Equations ◽  
Film Flow ◽  
Nonlinear Evolution Equations ◽  
Rupture Time ◽  
Initial Disturbance ◽  
Horizontal Plate ◽  
Film Rupture ◽  
Micropolar Liquid

AbstractThis paper investigates the rupture problem of a thin micropolar liquid film under a magnetic field on a horizontal plate, using long-wave perturbation to resolve nonlinear evolution equations with a free film interface. The governing equation is resolved using a finite difference method as part of an initial value problem for spatial periodic boundary conditions. The effect of a micropolar liquid under a magnetic field on the nonlinear rupture mechanism is studied in terms of the micropolar parameter, R, the Hartmann constant, m and the initial disturbance amplitude, H0. Modeling results indicate that the R, m and H0 parameters strongly affect the film flow. Enhancing the micropolar and magnetic effects is found to delay the rupture time. In addition, the results show that the film rupture time increases as the values of initial disturbance magnitude decrease. The micropolar and magnetic parameters indeed play a significant role in the film flow on a horizontal plate. Moreover, the optimum conditions can be found to alter stability of the film flow by controlling the applied magnetic field.

Experiments on the Splashing Limit During Drop Impact Onto a Thin Liquid Film

2017 ◽  
Author(s):  
Sota Kitabayashi ◽  
Koji Enoki ◽  
Tomio Okawa
Keyword(s):  
Film Thickness ◽  
Liquid Film ◽  
Weber Number ◽  
Silicone Oil ◽  
Pure Water ◽  
Thin Liquid Film ◽  
Severe Accident ◽  
Ohnesorge Number ◽  
Secondary Droplet ◽  
Droplet Production

The phenomenon of secondary droplet production during single drop impingement onto a liquid film is encountered in many industrial situations. Typical examples in the field of nuclear engineering are the spray cooling of hot surface and the atomization of radioactive liquids in severe accident. Therefore, the prediction of the onset of secondary droplet production is very important. It is known that the two types of droplet splashing mechanisms are present: the prompt splash and the late splash. The main purpose of this research is to determine the splashing limit separately for the prompt splash and the late splash. It is expected that the splashing limits are expressed using the three dimensionless numbers: the Weber number, the Ohnesorge number, and the dimensionless film thickness. Experiments were hence carried out using pure water and silicone oil as the working liquid. The experimental ranges were 129–606 for the Weber number, 0.00183–0.00300 for the Ohnesorge number, and 0.13–3.0 for the dimensionless film thickness. It was found that the occurrence of splashing can be predicted more accurately if the splashing limit is evaluated separately for the prompt splash and the late splash.

Cooling of Microelectronics by Shear-Driven Liquid Films

2006 ◽  
Author(s):  
Oleg Kabov
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
High Speed ◽  
Liquid Films ◽  
Vapor Flow ◽  
Air Cooling ◽  
Film Rupture ◽  
Computer Chips ◽  
Speed Computer ◽  
Very High

The recent development of microelectronics is closely linked to the problem of thermal regulation. The levels of heat generation in high-speed computer chips are now approaching very high values and they are on the edge of exceeding the capabilities of today’s air-cooling techniques. Thin liquid films may provide very high heat transfer intensity and may be used for cooling of microelectronics. A particularly promising technological solution is a set-up where heat is transferred to a very thin liquid film driven by a forced gas or vapor flow in a micro-channel. However, development such a cooling system requires significant advances in fundamental research, since the stability of joint flow of liquid film and gas is rather complex problem. Flow patterns, heat transfer laws and film rupture mechanisms for shear-driven locally heated liquid film flows remain only partially understood. The paper focuses upon shear-driven liquid film evaporative cooling of high-speed computer chips. The recent progress that has been achieved through conducting theoretical and numerical modeling as well as new experimental data has been discussed.

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