Liquid film characteristics in vertical two-phase flow

The motion of a liquid film falling under the action of gravity and of a co-current gas flow, was investigated. The fact that all processes arising in such a system are stochastic, induces the use of statistical parameters to describe the flow. The probability distribution and spectral density of the interface were measured and used to obtain the average characteristics of the waves, as: wave separation, wave propagation velocity, and wave profile. As a preliminary study of the gas-liquid interactions, the spectral density of wall pressure fluctuations were measured and used to estimate the average force on the liquid, assignable to those fluctuations. The Reynolds number for the liquid phase was varied between 1000 and 5000 and for the gas phase, between 0 and 60,000. Using a model whereby the waves are treated as behaving in a manner similar to the shot-noise process, it was shown to be possible to obtain an approximate solution of the boundary layer equations to describe the stochastic motion of a laminar liquid film.