A Numerical Study Of Gas-liquid Two-phase Flow In Boundary Layer

In engineering,there has been widely application about unsteady gas-liquid two-phase flow in boundary layer.For example,the technology of ventilated drag reduction can reduce energy consumption and environmental pollution.At temporal and spatial scales,temporary distribution and evolution rule of gas-liquid two-phase are the key causes to influence skin friction.In the last 15 years,the problem has been investigated by the mean of numerical simulations combining with experiments.In this paper,the finite volume element method based on VOF model coupled with continuous surface tension and standard k-?turbulence model is adopted to solve unsteady RANS equations,the evolution of ventilated flow and the resultant performance of drag reduction in flat plate boundary layer has also been studied.The credibility of the proposed numerical method is verified by comparing the numerical results with the experimental data.Then,a series of simulations are calculated to analyze the bubble size,near-wall mean void fraction,and performance of drag reduction quantificationally under different Re and ventilated flux.Besides,this paper establishes a simplified 3D model based on engineering application,and analyzes the integration influence of gas-liquid two-phase according to different ventilated structure parameters(including the arrangement of ventilated hole and the circular distances between holes).The research shows that in the transition drag-reduction mode,the periodic evolution of bubble is corresponding to periodic variation of drag reduction rate.The bubble size distribution is asymmetric and list to port,and distribution tendency is similar to logarithmic normal distribution.In this paper,the mean void fraction rose sharply with increasing distance from the near wall and then slowly decreases until it is zero.With the increase of Re,the near-wall mean void fraction increases a lot in the range of0(27)y/?_R _e?0.02,and drag reduction effect is promoted.With the increase of ventilated flux,the near-wall mean void fraction increases a lot in the range of0(27)y/?_R _e?0.6,and drag reduction effect is increased.Because of the low viscosity of gas,the increase of near-wall void fraction can improve the performance of drag reduction.In the air layer drag reduction mode,the evolution of air layer is corresponding to the performance of drag reduction.The mean void fraction of is close to 100%in the area of stable air layer.Because of the low viscosity of gas,the drag reduction is close to 100%.Both the increase of Re and ventilated flux can accelerate the advance of air layer and improve the performance of drag reduction.The 3D simulation also shows the close link between the integration influence of gas-liquid two-phase and the ventilated structure parameters...