Analysis of potential flow networks: Variations in transport time with $discrete$, $continuous$, and $selfish$ operation

Abstract

In potential flow networks, the equilibrium flow rates are usually not proportional to the demands and flow control elements are required to regulate the flow. The control elements can broadly be classified into two types - discrete and continuous. Discrete control elements can have only two operational states: fully open or fully closed. On the other hand, continuous control elements may be operated in any intermediate position in addition to the fully open and fully closed states. Naturally, with their increased flexibility, continuous control elements can provide better network performance, but $to~what~extent$? We consider a class of branched networks with a single source and multiple sinks. The potential drop across edges ($\Delta H$) is assumed to be proportional to the $n^{th}$ power of flow rate ($Q$), i.e., $\Delta H=kQ^n$ , ($n>=1$). We define $\textbf{R}$ as the ratio of minimal operational times required to transport a given quantum of material with either type of control element and show that $1\leq \textbf{R}\leq m^{\left(1-1/n\right)}$, where $m$ is the maximum depth of the network. The results point to the role of network topology in the variations in operational time. Further analysis reveals that the selfish operation of a network with continuous control valves has the same bounds on the price of anarchy.