scholarly journals Spanwise structuring and rivulet formation in suspended falling liquid films

2021 ◽  
Vol 6 (8) ◽  
Author(s):  
Manuel Rietz ◽  
Reinhold Kneer ◽  
Benoit Scheid ◽  
Wilko Rohlfs
Keyword(s):  
Liquid Films ◽  
Falling Liquid Films ◽  
Rivulet Formation

HEAT TRANFER PHENOMENA IN FALLING LIQUID FILMS: A SYNERGISTIC EXPERIMENTAL AND COMPUTATIONAL STUDY

2018 ◽  
Author(s):  
Alexandros Charogiannis ◽  
Fabian Denner ◽  
Berend G. M. van Wachem ◽  
Serafim Kalliadasis ◽  
Christos N. Markides
Keyword(s):  
Computational Study ◽  
Liquid Films ◽  
Falling Liquid Films

Dynamics of Developing Laminar Non-Newtonian Falling Liquid Films With Free Surface

1978 ◽  
Vol 45 (1) ◽  
pp. 19-24 ◽  
Author(s):  
V. Narayanamurthy ◽  
P. K. Sarma
Keyword(s):  
Liquid Film ◽  
Power Law ◽  
Mathematical Formulation ◽  
Liquid Films ◽  
Interfacial Shear ◽  
Newtonian Liquid ◽  
Power Law Model ◽  
Falling Liquid Film ◽  
Falling Liquid Films ◽  
Special Case

The dynamics of accelerating, laminar non-Newtonian falling liquid film is analytically solved taking into account the interfacial shear offered by the quiescent gas adjacent to the liquid film under adiabatic conditions of both the phases. The results indicate that the thickness of the liquid film for the assumed power law model of the shear deformation versus the shear stress is influenced by the index n, the modified form of (Fr/Re). The mathematical formulation of the present analysis enables to treat the problem as a general type from which the special case for Newtonian liquid films can be derived by equating the index in the power law to unity.

Capillary Flow Separation in 2- and 3-Dimensional Laminar Falling Liquid Films

2010 ◽  
Author(s):  
Georg F. Dietze ◽  
Reinhold Kneer
Keyword(s):  
Heat Transfer ◽  
Flow Separation ◽  
Capillary Flow ◽  
Capillary Wave ◽  
Liquid Films ◽  
Transport Processes ◽  
Gravitational Acceleration ◽  
3 Dimensional ◽  
Wave Region ◽  
Falling Liquid Films

Due to the selective use of liquid films in specialized technical equipment (e.g. new generation nuclear reactors), a fundamental understanding of underlying momentum and heat transport processes inside these thin liquid layers (with a thickness of approximately 0.5 mm) is required. In particular, the influence of surface waves (which develop due to the film’s natural instability) on these transport processes is of interest. For a number of years, experimental and numerical observations in wavy falling liquid films have suggested that momentum and heat transfer in the capillary wave region, preceding large wave humps, undergo drastic modulations. Indeed, some results have indicated that upward flow, i.e. counter to the gravitational acceleration, takes place in this region. Further, evidence of a substantial increase in wall-side and interfacial transfer coefficients has also been noted. Recently, Dietze et al. [1,2] have established that flow separation takes place in the capillary wave region of 2-dimensional laminar falling liquid films, partially explaining the above mentioned observations. Thereby, it was shown that the strong third order deformation (i.e. change in curvature) of the liquid-gas interface in the capillary wave region causes an adverse pressure gradient sufficiently large to induce flow detachment from the wall. In the present paper, a detailed experimental and numerical account of the capillary flow separation’s kinematics and governing dynamics as well as its effect on heat transfer for two different 2-dimensional flow conditions is presented. Experimentally, velocity measurements (using Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV)) and film thickness measurements (using a Confocal Chromatic Imaging technique) were performed in a specifically designed optical test setup. On the numerical side, simulations of the full Navier-Stokes equations as well as the energy equation using the Volume of Fluid (VOF) method were performed. In addition to the 2-dimensional investigations, the characteristics of capillary flow separation under 3-dimensional wave dynamics were studied based on the 3-dimensional numerical simulation of a water film, which was previously investigated experimentally by Park and Nosoko [3]. Results show that flow separation persists over a wide area of the 3-dimensional capillary wave region, with multiple capillary separation eddies occurring in the shape of vortex tubes. In addition, strong spanwise flow induced by the same governing mechanism is shown to occur in this region, which could explain the drastic intensification of transfer to 3-dimensional liquid films.

Thermal Entry in Falling Liquid Films at High Reynolds Numbers

2011 ◽  
Vol 6 (4) ◽  
pp. 51-54
Author(s):  
Evgeny Chinnov ◽  
Sergey Abdurakipov
Keyword(s):  
Experimental Study ◽  
Reynolds Numbers ◽  
Liquid Films ◽  
Field Methods ◽  
Entry Length ◽  
Temperature Measuring ◽  
Strong Wave ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Falling Liquid Films

An experimental study of thermal entry length in falling liquid films at high Reynolds numbers was performed with the use of field methods for thickness and temperature measuring. It was shown that the combination of the strong wave and thermocapillary effects leads to a significant decrease of thermal entry length

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