Two-dimensional direct numerical simulations have been performed in order to investigate the surface waves of falling films in the cases of three kinds of working fluids by using MARS (Multi-interfaces Advection and Reconstruction Solver) method. The surface waves can be controlled by an external artificial velocity oscillation. Although the amplitude of the artificial velocity oscillation is very small, the disturbances create small surface waves and eventually they develop to large surface waves consisting of solitary waves and capillary waves due to instability of falling films. The numerical results indicate that the characteristic of these two-dimensional waves can be divided into three groups with Weber number and frequencies of disturbances. Moreover the numerical results indicate the surface groups play an important role on the heat transfer.
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