Flow transition of magnetohydrodynamic bubbly jet driven by Lorentz force

Abstract

Background: Magnetohydrodynamic (MHD) jet in saltwater possesses potential applications to improve marine vehicle propulsion and hydrogen collection. In the present paper, pattern and flow transition of MHD bubbly jets are studied. Bubbles of oxygen and hydrogen, produced by electrolysis in saltwater and displaced by the Lorentz force, form a typical multiphase MHD jet flow.Methods: Taking advantage of the brightness of gaseous bubbles, emergence of bubbly jet can be directly observed. Pattern of the bubbly jet is experimentally confirmed to resemble the saltwater jet, and used for further analysis.Findings: A Lorentz-force based Reynolds number ReL is proposed to demonstrate the pattern similarity of the MHD jet, and thus applied to categorize the transition of flow regimes from laminar to turbulent. For a jet of lower ReL, the pattern of the bubbly jet appears as a continuous, wavy and laminar stream. Turbulent breakups start to evolve at farther downstream of the bubbly jet once the ReL exceeds a critical value. The critical value of ReL≈1500 is verified both by visual observation and relevant quantitative measures of the bubbly jet.