Three-dimensional simulation on behavior of water film flow with and without shear stress on water–air interface

Abstract

In this paper, the simulations of falling film behaviour on a flat plate with and without interfacial gas-liquid shear stress were carried out. A three-dimensional numerical model was established based on film flow characteristics. A source term was implanted into the numerical model to take into account the interfacial gas-liquid shear stress. The model was validated by the experimental data. Both continuous film flow and film breakup were simulated. The film thickness, velocity distribution and wall shear stress at different Reynolds numbers were presented to understand the film flow behaviour comprehensively. The influence of water-air shear stress on film flow behaviour was revealed. A reasonable prediction on both MWR (Minimum Wetting Rate: Δ min) and MLFT (Minimum Liquid Film Thickness: Γ min) were obtained. The model proposed in this study ought to be profitable for studies on mechanism of film breakup.

Three-Dimensional Mathematical Model of the Liquid Film Downflow on a Vertical Surface

“…A new empirical model and an improved minimal surface model were developed based on experimental data and used to predict the hydrodynamic entrance length. However, usage of the VOF model for the laminar wavy motions of liquid film flow over flat surfaces in combination with the CSF (Continuum Surface Force) model gives good agreement with the experimental data [8,9].…”

“…Additionally, equations for determining the averaged film thickness, the averaged velocity vectors over the film thickness, the longitudinal and vertical velocity components, and the initial angle of streamline deviation from the vertical axis were analytically obtained.Energies 2020, 13, 1938 2 of 15 the fluid film movement, heat and mass transfer in column equipment, the separation of gas-liquid mixtures, and fluid flow in heat exchangers. Scientists for the above purpose have investigated the heat and mass transfer processes occurring in microchannels [3][4][5][6] and free and induced liquid film flow over different surfaces [7][8][9][10][11][12][13][14][15][16][17][18] and inside of different channels [19][20][21][22][23][24][25]. This flow occurs due to the influence of various forces, which determine the film formation or destruction, and the inclination angle of the surface.…”

“…A new empirical model and an improved minimal surface model were developed based on experimental data and used to predict the hydrodynamic entrance length. However, usage of the VOF model for the laminar wavy motions of liquid film flow over flat surfaces in combination with the CSF (Continuum Surface Force) model gives good agreement with the experimental data [8,9].For better accuracy and further improvement of the results obtained by CFD (Computational Fluid Dynamics) methods, the authors of the study [10] implement the MAC (Marker and Cell) and the moving grid. The application of the VOF model is enough for the study of a non-Newtonian liquid film [11].…”

Numerical simulation of the behavior of high‐viscosity fluids falling film flow down the vertical wavy wall

“…Even though average film thickness reveals an averaging characteristic for falling film flow, the probability density function (PDF) of film thickness is considered to be an effective variable that can reflect more information on film flow behavior . In this study, the film thickness scatters in a wide range owing to the wavy wall, especially in the case of ultra‐high‐viscosity fluid.…”

Flow Characteristics of the Vertical Turbulent Falling Film at High Reynolds Numbers

“…Interfacial waves can stimulate the transport of falling films by increasing the interfacial area, decreasing the mean film thickness, and enhancing the turbulence intensity, and then the local heat transfer coefficient near the interface waves will be significantly changed . However, falling films are easy to break if they are too thin, which may cause the drywall problem and even endanger the device safety. ,, …”