Numerical Simulation Of Transient Flow In Rapid Drainage Process Of Pipelines

In modern urban planning,the design of underground drainage system is a very important work,it is directly related to the basic life of residents and the economic development of the city,and plays a direct decisive role.The unsteady hydraulic process in the pipeline affects the drainage system by increasing the damage risk of infrastructures.Therefore,in order to design and build proper drainage systems,it is of great importance to study the transient process under different flow conditions in the pipeline system.In order to study the flow state of the fluid in the pipeline,we introduced governing equations and boundary conditions in both Eulerian and Lagrangian frameworks.Then,the numerical methods commonly used in pipe flow are introduced,such as mesh-based methods and meshless methods.The Smoothed Particle Hydrodynamics(SPH)method and its modified algorithms are deduced in detail.The transient flow problem involved in the pipeline drainage system concerned in this paper is decomposed into four sub-problems.For the study of transient phenomena such as water hammer and rapid opening of valve,the water hammer equations in Lagrangian form is adopted in this paper and the SPH method is used for solving them.The results are compared with those obtained by the method of characteristics.In addition,to analyze the complex transient problems in rapid drainage process of a deep dropshaft and a large-scale pipeline,a simplified mathematical model is established based on conservation principles.The validity of the meshless methods in solving transient flow in pipelines is verified by solving the traditional water hammer problems with instantaneous value closing and opening.The proposed model for rapid emptying of pipelines is validated against physical experiments and the numerical results in literature.The hydraulic characteristics and several influencing factors are revealed.The accumulated experience for the study of transient flow in rapid pipe emptying process provides theoretical guidance for the design and construction of drainage system.