Difference Analysis of Water Head and Travel Time Before and After Simplification of Flow Along Link

Abstract:

In order to reduce the workload of modeling and calculation of water distribution systems， the hydraulic equivalent method or flow equal division method is often used to simplify the flow along the link， which distributes the flow along the link to the upper and lower nodes of the link. In order to explain theoretically the influence of simplification of the flow along the link， the differences of water head and traveling time before and after simplification of the general flow along link were analyzed， and the differences of water head and traveling time before and after simplification of the uniform flow along the link were analyzed. These two aspects were calculated and discussed in combination with cases. It is concluded that the hydraulic equivalent simplification ensures that the water head at the upper and lower nodes of the link is the same as that before the simplification， while the water head at each point in the link before and after the simplification is usually different. After hydraulic equivalent simplification， the flow distribution ratio of the upper node is related to the number of demand points in the link and the flow proportion along the link， but has nothing to do with the diameter， the upper node head， the inlet flow， the length and the friction coefficient of the link， The simplification method is suitable for the extend period simulation model with variable water head at the upper node or link inlet flow. The uniform discharge along the link is treated according to the hydraulic equivalent method （or flow equal division method）， which is suitable for simplifying the flow along the link where the internal flow along the link accounts for a small proportion （the links close to the water treatment plant）.

Key words:water distribution system;flow along the link;hydraulic equivalent;flow equal division;travel time