2014 1(14)

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   Short abstract

 

Pages:

115 - 120

Language:

RU

Ref.:

10


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2014_1(14)_19.pdf

 

 

SIMULATION OF WAVES IN THE VERTICAL RIVULET

Aktershev S.P., Alekseenko S.V., Bobylev A.V., Markovich D.M., Kharlamov S.M.

Institute of Thermophysics SB RAS, Novosibirsk, Russia


Citation:

Aktershev, S.P., Alekseenko, S.V., Bobylev, A.V., Markovich, D.M. and Kharlamov, S.M., (2014) Simulation of waves in the vertical rivulet, Modern Science: Researches, Ideas, Results, Technologies, Iss. #1(14), PP. 115 - 120.


Keywords:

rivulet flow of liquid; forcing waves; numerical simulation


Abstracts:

The type of a film flow when the liquid drains off in the form of assemblage of streams, it is accepted to name rivulet flow, and the separate stream restricted to two contact lines is named rivulet. Rivulet flow regime is formed under the influence of various factors, such as gas stream, evaporation, non-uniformly wetted or structured surface, etc. Thus, for example, rivulets develop at the front of the liquid film, flowing down over a solid wetted surface. Rivulet-type flow is also observed at break of non-isothermal liquid film due to thermo-capillary effect or boiling up, accompanied by formation of dry spots. The special attention to rivulet flow is caused by its applied value as such flow is realized in various apparatuses of power engineering and chemical industrial engineers  in absorbers, rectifying columns, evaporators and so on. In comparison with a uniform liquid film, the rivulet dynamic has a number of features (presence of a mobile contact line, a hysteresis of an angle of wetting, meandering). Therefore the theoretical description of rivulet flow is rather complex problem, and the information about these specific features is available mainly from experiments. Rivulet flow as well as a film flow can be unstable relative to external perturbations; thus on a rivulet surface the waves essentially influencing hydrodynamics and heat transfer develop. It is necessary to note, that in the literature practically there is no both theoretical, and an experimental description of wave regimes of rivulet flow. The majority of theoretical papers are devoted to steady waveless rivulet. In the given paper numerical simulation of the three-dimensional forced waves on a surface of vertical rivulet for the first time is presented. To describe the waves in rivulet the Kapitza-Shkadov approach is used. In numerical calculations the characteristics of linear and nonlinear regular waves depending on forcing frequency are gained at various values of a Reynolds number and a wetting angle. Comparison of results of calculations to available experimental data is presented. Comparison has shown that the used model as a whole adequately presents the wave surface form of rivulet, but gives the underrated values of a wave velocity and, accordingly, wave length. The applied model used in general describes adequately the shape of the waves on the rivulet surface at moderate Reynolds numbers. In particular, for WGS-rivulet ("small" contact wetting angle) the model predicts waves of step-wise shape, which were observed in the experiments at low frequencies. For moderate forcing frequencies the model predicts waves with capillary ripples in front of wave peak. The shape of these waves is in good agreement with the experimental data. The calculations have shown that for a wave rivulet flow, the value of contact wetting angle pulsates in accordance with the wave amplitude and phase.


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