Numerical Simulation Of The Ventilation Flow Field With Liquid Cross Flow

The phenomenon of ventilation flow field from a circular orifice with liquid cross flow widely appears in the fields of underwater weapons,ships,chemical industry,etc.,and is used to change the mechanical environment or to control the process of chemical reactions between gas and liquid.The characteristics of multiphase,transient,multifactor,multiscale and other characteristics of the flow field indicate the complexity of the flow.Gravity,viscous force,surface tension,and gas compressibility all play important roles.The scientific issues include bubble flow,gas jet,bubble drag reduction,and ventilated bubble flow,etc.Among them,the study of the shape evolution law of the bubble and the water-air interaction mechanism have important scientific significance and application value.In this paper,a numerical study was conducted on the ventilation flow field from a single circular hole in a flat plate with the action of horizontal water flow.Firstly,based on the finite volume method,combined with the VOF interface capture method and the large eddy simulation（LES）method,a commercial engineering software（FLUENT）was used to establish a numerical simulation method for the ventilation multiphase unsteady flow field with lateral flow.The accuracy of the numerical simulation method was verified by comparison with the shape and characteristic parameters of bubbles in relative experiments.Next,the flow characteristics of the flow field of the horizontal plate was analyzed,including the evolution of the shape of the bubbles;the development law of the characteristic size parameters;the characteristics of the surface fluctuations of the bubbles;the pressure and velocity characteristics of the flow field.The characteristic size parameter increases almost linearly with time to the maximum size and then falls off precipitously;the surface of the bubble near the hole has obvious fluctuation characteristics;the pressure inside the bubble is generally greater than the external pressure,which promotes the growth and expansion of the bubble;the velocity of the flow field near the hole reachs the maximum,and there is a backflow in the area close to the wall.In the case of different ventilation flow rates and lateral flow velocities,the bubble growth rate,the maximum dimensionless bubble length is linearly related to the dimensionless ventilation flow rate,and the Reynolds number of the lateral flow;There is a quadratic function relationship between bubble breakup frequency and the Reynolds number of the lateral flow.Finally,based on the numerical simulation of the ventilation flow field of the inclined plate at different ventilation flow rate and lateral water flow velocities,by processing the flow field simulation data,development law of flow was obtained at three different inclination angles: positive inclination,zero inclination,and negative inclination.The maximum length of bubbles in the flow field of the negative inclined plate is the largest,and it is easy to form longer bubbles.Velocity distributions of positive inclination and zero inclination flow field are similar.Within the scope of the study,the maximum length of the bubbles in all three operating conditions increase with the increase of ventilation flow rate and lateral water flow velocity.