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This article presents the results of numerical simulations of three-dimensional waves on the surface of a rivulet flowing down a vertical plate. The Kapitza–Shkadov approach is used to describe the wave flow of the rivulet. Various characteristics of linear and nonlinear regular waves in the rivulet are obtained through numerical calculations as a function of the forcing frequency at different Reynolds numbers and contact wetting angles. The results of the simulations are compared with the authors’ previous experimental data. The comparison shows that the applied model adequately describes the shape of the wave surface of a rivulet, although the wave propagation velocity and wavelength are underestimated.

UDC 536.423 S. P. Aktershev and V. V. Ovchinnikov Steady propagation of the boundary of a vapor cavity in a layer of a metastable liquid along the heater surface is considered. The temperature and velocity of interface propagation are determined from the equations of conservation of mass, momentum, and energy in the neighborhood of the stagnation point of the vapor cavity and the condition of stability of steady motion of the interface. It is shown that a solution of these equations exists only if the liquid is heated above a threshold value. The calculated velocity of interface motion and the threshold value of temperature are in reasonable agreement with available experimental data for various liquids within wide ranges of saturation pressures and temperatures of the superheated liquid.Introduction. The problem of growth of the vapor phase in a superheated liquid is important for understanding the fundamental features of the boiling process. In the general statement, this problem is extremely complicated, because the growth of the vapor phase depends on many interrelated factors: heat-transfer intensity, evaporation kinetics, liquid dynamics, etc. The experiments [1-4] revealed degeneration of the bubble boiling mode, when already the first emergence of the vapor phase led to formation of a stable vapor film, skipping the bubble boiling mode (third crisis of heat transfer). It was demonstrated [4] that there exists a lower boundary of superheating prior to incipience for the third crisis, and the values of heat fluxes in such a situation are lower than the values of the first critical flux. In this case, instability starts to develop in the contact zone between the vapor bubble surface and the heater, and conical vapor cavities propagating along the heater are formed (Fig. 1).It was shown [5, 6] that the stagnation point of a conical vapor cavity (evaporation front) moves with a constant velocity. The velocity of the evaporation front substantially depends on liquid superheating and can reach tens of meters per second. The data on the evaporation front velocity for various organic liquids, water, and liquid nitrogen, were obtained in [5][6][7][8][9][10][11]. The experiments were performed at pressures both below and above the atmospheric value, with the use of a cylindrical heater and a plane heater under conditions of quasi-steady heating and a stepwise increase in power. It should be noted that the character of motion of the evaporation front is considerably different from the character of motion of the incipience wave, when the incipience zone consisting of isolated growing vapor bubbles propagates along the heated surface with an approximately constant velocity [6,8]. In contrast to the incipience wave, the evaporation front is a moving interface. If the superheating is close to the threshold value, either the evaporation front or the incipience front can be observed; a transition from the incipience front to the evaporation front is also possible [8].The evaporation front has some specific features and is ...

Nonlinear wave formation and heat transfer in wavy condensate film flowing over the isothermal wall are studied numerically. The integral-boundary-layer model, modified with account of the phase transition has been used to describe the wave motion. The nonlinear evolution of both natural and forced two-dimensional waves was investigated, and wave effect on heat transfer in condensate film was determined. Heat transfer enhancement by waves due to the predominant contribution of the thin residual layer between the peaks was demonstrated. It is shown that by applying the superimposed periodic oscillations, one can intensify heat transfer within a certain range of frequencies as compared to the case of naturally occurring waves.