Theoretical analysis and experimental investigation of air-bubble-stream-induced water circulation

Abstract

Air-bubble curtain is an amount of air injected vertically into a water body. The generation of such a flow and the lack of a continuous interface cannot be described by a smooth mathematical function. Therefore, a two-phase flow model is introduced. A numerical model for the concurrent flow of buoyant bubbles continuously flowing into a 2D water field, and the water flow (generated by the bubbles), is formulated and solved. The two-phase flow model consists of the 2D Navier equations for the water phase (continuous phase) and of the active Lagrangian particles for the simulation of the air bubbles (discrete phase). The coupling of the two phases is done through the continuity and the momentum equilibriums. The numerical solution by explicit second-order Finite Differences (FD) scheme leads from a cold start to steady flow conditions, resolving for the water velocities vector field and the air bubbles’ concentration distribution. The flow configuration is repeated in laboratory conditions, and the velocity field is measured by the particle image velocimetry (PIV) technique. In this work, the numerical two-phase flow model and the hardware aspects of our measurement device are analyzed, followed by the comparison of the numerical and experimental results. This empowers the validity and credibility of the algorithm introduced. Finally, interesting conclusions are drawn regarding the operational use of the model.