Slug-flow force balance

Chum flow or slug flow-annular (dispersed) flow transition. The flow becomes annular when the gas flow rates are enhanced to a certain point. The high gas flow rate causes a wavy interface of the liquid film. As a consequence, parts of the waves will enter the gas core as entrained drops. This results in an upward flow direction of the liquid, due both to interfacial shear and to drag on the waves and drag on the droplets. Annular flow can therefore exist only when the gas velocity is sufficient to lift the droplets in the gas core. The minimum gas velocity required to suspend a drop is determined from the balance between the gravity and drag forces on the drop. 

Boundary B delineates the condition that prevents the possibility of strand flow over the stationary layer. The model established in this work to predict the boundary of low-velocity slug-flow is based on this understanding and the theory of mass, force and momentum balance. 

An investigation into the boundary of low-velocity slug-flow pneumatic conveying has been conducted experimentally and theoretically. The mechanism for the formation of the imstable zone has been developed. Based on mass, force and momentum balances and the unstable zone mechanism, a theoretical model for the prediction of the unstable zone boundary has... 

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