Stability of Annular Flow and Flow Pattern Transition to Churn Flow
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In the vertical upward gas-liquid two-phase flow under low liquid flow rate conditions, the flow patterns are divided into three main groups; annular flow, churn flow and slug flow. At high gas flow rate, the annular flow is formed with continuous gas core and liquid film on the wall. As the gas flow rate decreases, the liquid film flow on the wall becomes unstable owing to a reduction of the gas-liquid interfacial shear stress, which can trigger the flow pattern transition to the intermittent slug flow. In the intermediate region between annular and slug flows, the churn flow is observed. As the name "churn" implies, the flow is very complex and accompanied with oscillatory motions of the liquid in the tube. <BR>In the present paper, a lumped parameter model is developed to predict the stability of annular flow and simulate the non-linear oscillation of churn flow. The model is based on the one-dimensional two-fluid model. According to the assumption of uniform flow, the annular flow is expressed by a set of ordinary differential equations. From the comparison between the linear stability analysis and the flow pattern map in the experiment, it is found that the flow pattern transition from annular to churn flow is in approximate agreement with the marginal stability boundary of the model, and the churn flow oscillation induces the formation of intermittent slug flow.
- Proceedings of the Japan Society for Photoelasticity
Proceedings of the Japan Society for Photoelasticity 8, 25-30, 2008-06-25
The Japanese Society for Experimental Mechanics