输配水系统明满瞬变流全窄缝数值模型

Full narrow-slot numerical model of open-pressurized transient flows in water distribution system

发生在输配水系统中的明满流交替过程是引起系统破坏的主要原因之一。准确模拟发生在输配水系统中的混合明满流瞬变过程,是亟须解决的技术难题之一。然而,常用的Preissmann窄缝法无法模拟含负压流的瞬变过程,很大程度上限制了该数值模型的适用范围。本文耦合二分压力法及Preissmann负窄缝思想,建立了一套可模拟求解非恒定明流、含负压的有压瞬变流及含负压的明满交替混合流数值模型,并基于CFL约束条件提出了对负压流与明流的判别方式。通过明渠充水、有压管道水锤及充水过程中关阀形成的明满流交替及水锤同时作用的复杂算例表明:本文所建模型突破了传统Preissmann窄缝法不能模拟负压的局限及二分压力法判别明流及满管负压流的困难,实现了对不考虑气液两相相互作用下的明满交替瞬变流的准确模拟。

The alternating process of open-channel and pressurized flows in a water distribution system is a major cause of system damage.Accurate simulation of the transient process of mixed open-pressurized flow in water distribution systems is a technical problem that urgently needs to be solved.However,the commonly used Preissmann narrow slot method cannot simulate the transient process with negative pressure flow,greatly limiting its applicability to these systems.This paper develops a numerical model for unsteady open-channel flow,pressurized transient flow with negative pressure,and open-pressurized mixed flow with negative pressure,through coupling the dichotomy pressure method and the Preissmann negative slot idea.We develop a method for distinguishing negative pressure flows from open-channel flows based on the CFL constraints,and apply the model to complicated flow cases-open-pressurized flow alternation and simultaneous action of water hammer during open channel filling,water hammer in the pressurized pipeline,and valve closing during the filling.The applications show that our new model breaks through the limitation of the Preissmann method and the difficulty in distinguishing open-channel flows and negative pressure flows by the differential pressure method,and achieves accurate simulations of open-pressurized alternation transients without gas-liquid two-phase interaction.