EFFICIENT VALVE REPRESENTATION IN FIXED-GRID CHARACTERISTICS METHOD

This work formulates a unified set of boundary conditions to efficient ly represent the majority of valve and orifice devices found in water supply, transmission, and distribution systems. A particularly useful combination of mathematical components results when a lumped inertia m odel is linked with a throttling device. This combination of elements, termed a pipe replacement element/valve-in-line (PREVIL), has been co nstructed to permit a wide range of control-valve/short-pipe combinati ons to be conveniently modeled with the method of characteristics. The solution is quadratic in form and explicit, regardless of the number of pipes that are connected to the boundary condition. A variety of on -off and modulating valves can be accurately handled within this frame work. An additional feature developed in this treatment of pressure-re ducing and pressure-sustaining valves, how controllers, and other simi lar devices permits a more realistic representation of these important control devices. The response time of the regulating valve on opening or closing can be readily approximated so that a greater range of con trol behavior can be simulated. Application of the combined boundary c ondition is illustrated in a pipe network.