Research On Bubble Motion Characteristics Under Isotropic Turbulent Flow

The "poor,fine,miscellaneous,and difficult" characteristics of mineral resources are the main reasons that restrict their efficient recycling.Flotation is one of the main methods to achieve mineral separation.The theory of flotation kinetics indicates the collision probability of bubbles and mineral particles.It is the key to influence the efficiency of mineral flotation,and the movement characteristics of bubbles directly affect the collision of bubbles and particles.The mineral flotation process is in a complex turbulent environment.To carry out research on the law of bubble motion in a turbulent environment to clarify the relationship between bubble motion and the turbulent environment is of great significance to the design of the flow field of flotation equipment and the improvement of mineral flotation efficiency..In this paper,we first use grids to excite isotropic turbulence,and then carry out the study of bubble motion laws under isotropic turbulence.The specific research contents and conclusions are as follows:(1)The grid stimulates isotropic turbulence;four grids of different shapes are designed,and large eddy numerical simulations are carried out.The homogeneity and turbulence intensity on the center line of the pipeline after the grid are analyzed,and the optimal Grid structure;an experimental platform for grid excitation of isotropic turbulence was built,and the particle imaging system was used to photograph the flow field behind the grid at different flow rates,and MATLAB software was used to process the obtained flow field information,and the grid excited turbulence was obtained Generated isotropic turbulence information.It provides a basis for the study of the law of bubble movement in the isotropic turbulent region.(2)Generate bubbles of controllable size;the generation of size-controllable bubbles is the premise of the experiment.Using a high-speed dynamic system,the bubbles produced by different needles in static water and turbulent flow at different inflation speeds were photographed,and the Tata formula was carried out according to the experimental data.The correction is made,and the predictive relationship of the bubble diameter generated by the needle in the turbulent flow is obtained.(3)The characteristics of bubble motion in isotropic turbulent flow;the motion of bubbles in the acceleration section and the stable section were captured by a high-speed camera system,and the effects of bubble diameter,incoming flow velocity,turbulence intensity and other parameters on bubble aspect ratio,motion speed,and sliding The law of influence of moving speed.The following conclusions are drawn: the bubble movement speed first increases and then decreases with the increase of the bubble diameter,and the incoming flow velocity is the main factor affecting the bubble movement speed.The bubble aspect ratio decreases with the increase of bubble diameter,turbulence intensity,and incoming flow velocity.The bubble slip velocity first increases and then decreases with the increase of bubble diameter,increases with the increase of turbulence intensity,and decreases with the increase of incoming flow velocity.Finally,based on the experimental data,the empirical models of different motion speeds and aspect ratios are compared,and the prediction relations of bubble motion speed,aspect ratio and slip speed are obtained respectively.There are 56 pictures,7 tables,and 104 references.