Theory 36/Geometry & Scale/Water systems
Biofilms Follow the Pipe
The claim
Biofilm thickness in pipes is set by the ratio of pipe diameter to the mass-transfer boundary layer, so narrow pipes support thinner biofilms at the same flow.
01Mechanism
Nutrient delivery to the wall depends on the boundary layer, which scales with diameter; growth is limited by delivery rather than by flow.
02Prediction
Thickness should fall as the ratio falls.
03Refutation
Thickness tracking flow velocity would remove the geometric term.