Rivulet structures formation, rupture and heat transfer in the falling liquid films

Abstract

Abstract The evolution of three-dimensional waves into thermocapillary-wave structures, rivulets deflection, heat transfer enhancement and rupture vertically falling water film at heating were studied. Characteristics of the film flow were determined experimentally using simultaneous measurements of thickness and temperature fields on the falling heated liquid film surface (LIF and IR scanner). The amplitudes and velocities of waves, amplitudes of rivulet deflection, temperature fluctuations on the film surface, frequency spectra and pulsation energies were determined. Several different types of instability were registered on the surface of the heated fluid film: 3D hydrodynamic and thermocapillary A, B and C instabilities. The thermocapillary structures of type A arise in the residual layer behind the front of the wave, leading to an increase in the amplitude of the waves and rivulets deflection amplitudes. It is shown that the heat flux of rupture increases and intensity of heat transfer enhances due to an increase in the surface waves and rivulet deflection amplitudes.