Numerical Simulation And Total Flow Description Of Spout Flow And Pressured Pipe Flow

Spout flow and pressured pipe flow are two kinds of flow widely existed in engineering practice and study into their flow characteristics has long been drawing people's attention,thus numerous investigations have been carried out through experimental research,theoretical analysis and numerical simulation.In previous studies,researchers mainly focused on the flow field and total flow characteristics of pressured pipe flow,while little work has been done about spout flow.To be specific,the flow field characteristics were mainly studied by experimental research and numerical simulation,and the research of total flow characteristics mainly adopted the method of experimental measurements,by which the head loss coefficients of different boundary conditions are obtained.However,all the previous researches have failed to give a specific expression of energy loss,and numerical simulation is mainly performed using isotropic turbulence model.In this paper,the water flow movement is investigated through theoretical analysis and the numerical simulation of spout flow and pressured pipe flow;the main results are as follows:(1)Starting from the governing equations of incompressible viscous flow,calculation formulas of total flow energy loss and discharge capacity in spout flow and pressured pipe flow are given.Different from the half-empirical calculation methods in traditional hydraulics,the new formulas can directly reflect the effects of turbulence without having to determine the head loss coefficients by experiments,thus it provides a uniform description of flow field and total flow characteristics.(2)By using Reynolds stress model to close Reynolds time-averaged equations,a verification calculation on pipe flow in rectangular duct is conducted,and the calculating results of longitudinal mean-time velocity are in good accordance with experimental values.Through the validated mathematical model and numerical calculation method,a three-dimensional numerical simulation of spout flow is performed for further study,which gives us more in-depth understandings about its flow field characteristics from aspects of longitudinal mean-time velocity,mean-time pressure and turbulent kinetic energy,and then the flow coefficient is calculated with the proposed formula of discharge capacity.(3)Combining with calculation formulas of total flow energy loss and discharge capacity,two-dimensional numerical simulation of pressured pipe flow is carried out with targeted grid layout to accomplish the uniform description of flow field and total flow characteristics.By comparing local flow regime,longitudinal mean-time velocity,mean-time pressure,turbulent kinetic energy,total flow energy loss and flow coefficient under different calculating conditions,the impact of head water and bottom wall on the flow field and total flow characteristics is explored.The results show that:1)when the distance between the pipe and the bottom wall is more than 3 times the pipe height,the flow field in the entrance region of the pipe is hardly affected by the bottom wall,with the flow field exhibiting as complete contraction.What's more,when the flow field in the entrance region is not completely contracted,the total flow energy loss is the smallest among all the calculating conditions while the discharge capacity acts in the opposite way;2)when the water head is greater than 15 times the pipe height,it has little influence on total flow energy loss and discharge capacity.