Mechanisms that lead to violent geysers in vertical shafts

Supported with laboratory observations, this paper describes the mechanisms that lead to violent eruptions in stormwater and combined sewer systems. This paper also derives the upper limit for the geyser eruption velocity in these systems. The mathematical analysis shows that the maximum velocity of a gas–liquid mixture eruption in a vertical shaft is that of its mixture sound speed. The analysis also shows that the pressure gradient ∂p/∂z needs to increase substantially for the eruption velocity to approach the air–water mixture sound speed. The derived upper limit for the geyser eruption velocity is assessed using two test cases: a geyser event in a stormwater collection system in Minneapolis and our laboratory experiments.