管道瞬态多流态混合流的扩散对流模型  

Diffusion convection model for conduit multiregime transient-mixed flow

作　　者：张东 王恩志[1] 刘晓丽[1] 吴春璐 ZHANG Dong;WANG Enzhi;LIU Xiaoli;WU Chunlu(Department of Hydraulic Engineering,Tsinghua University,Beijing 100084,China)

机构地区：[1]清华大学水利水电工程系,北京100084

出　　处：《清华大学学报（自然科学版）》2023年第5期830-839,共10页Journal of Tsinghua University(Science and Technology)

基　　金：国家自然科学基金面上项目(52079068);国家自然科学基金重大项目(52090081);国家自然科学基金重点项目(41831290);陕西省科技厅联合基金项目(2021JLM-54)。

摘　　要：管道明-满流及混合流流动过程的数值模拟存在计算稳定性差、成本高的问题,尤其在如岩溶区长期水动力预测方面,急需准确、稳定性强且成本低的物理数学模型。基于扩散波动近似和密度连续假设,该文考虑管道流动形式及流态变化过程,提出了多流态管道混合流扩散对流模型,并针对典型管道流问题进行了数值模拟来验证模型的适用性和准确性。结果表明,该模型的计算结果与理论解、 SWMM(storm water management model)结果及实验数据十分吻合,准确地模拟瞬时管道混合流动过程。相比SWMM,该模型减弱了在明-满流交替界面的数值振荡现象,计算稳定性更好,对时空离散要求更低。该模型可以为管道长期水动力过程模拟预测如岩溶管道流模拟等提供理论和方法支撑。The evolution of free-surface and pressurized flows and their simultaneous occurrence(mixed flow)often appear in pipe drainage systems(e.g.,urban sewerage systems,water conveyance pipelines and karst conduits)due to variable inflow and outflow conditions.Accurately simulating the transition between free-surface and pressurized flows is of particular significance for infrastructural damage and operational control in engineering.However,the transition process between free surface-pressurized mixed flows in the channel and conduit leads to difficulties in numerical simulation and poor stability,especially in long-term hydrodynamic forecasting.Thus,an accurate,numerically stable,and low computational cost physical-mathematical model is urgently needed.Based on the diffusion wave approximation of the Saint-Venant equations,the water hammer equations are extended,and the fluid compressibility is considered to establish a linear relationship between fluid density and pressure head.The transition of flow regimes(free surface,pressurized,and mixed flow)during the flow process is also analyzed,and the Swamee-Swamee formula is adopted.A multiregime mixed flow diffusion convection model is then proposed in the paper.The model not only describes the evolution of flow types but also considers the transition of multiregime flows.Furthmore,the comparison between the proposed and previous models is conducted to demonstrate improvements and developments in the new proposed model.Numerical simulations for some benchmark questions are carried out and compared with previous models.The following results are presented.1)Regardless of free-surface or pressurized flow,an evolution and transition of laminar,transition,and turbulent flows are observed in the pipeline flow with the change in water depth or flow rate,and laminar and transition flow states cannot be ignored.2)The simulation results of the proposed model are close to those of the SWMM(storm water management model),which reach the requirements of engineering.The proposed model

关 键 词：管道流 明流-满流-混合流 扩散波动 扩散对流 多流态 

分 类 号：TV139.14[水利工程—水力学及河流动力学]