Generator
The two costs, and where their sum is least
Pumping cost falls as r⁻⁴ and upkeep rises as r². Minimising the sum gives flow proportional to r³ — checked here across flows of 0.6, 1.5, 2.4, where Q/r³ holds to 3.9%.
Drawn at its defaults, in branching and transport. It takes no options at all, so every essay calling it gets this exact drawing.
Called by 3 essays
the blast radius of changing it