수치모의를 이용한 배수관로의 혼합 흐름에 의한 유량 변동성 해석 = Analysis of flow rate variation by mixed flow in a drainage pipe using numerical simulation

다국어 초록 (Multilingual Abstract)

This study analyzes the characteristics of mixed flow occurring in a drainage pipe due to unsteady inflow using a numerical model. The numerical model utilizes the interIsoFoam solver in OpenFOAM to more accurately simulate the interface between air and water. To validate the model, it is applied to a slug flow experiment, demonstrating that the model effectively reproduces slug formation caused by water surface surges, as well as the movement and development of slugs. The characteristics of mixed flow in the pipe are simulated in a two-dimensional vertical plane under various air and water inflow conditions. To reproduce the unsteady nature of the water surface at the inlet boundary, a sinusoidal vertical velocity boundary condition is applied. Additionally, to analyze the flow rate variability induced by the mixed flow, the maximum outflow rate is calculated and compared against the inflow rate. Nine different mixed flow conditions are simulated. The results show that when both water and air velocities are sufficiently high, slugs formed and developed, leading to a maximum flow rate variability of 112.5%. In three-dimensional simulations, pressure flow is found to be more dominant, and the formation and development of the air layer differed from the two-dimensional results. In drainage pipes, the unsteady fluctuations in the inlet water level increase the likelihood of mixed flow formation. However, for mixed flow to persist along the pipeline and result in significant flow rate variability, sustained slug formation and development are necessary. This persistence depends on both the magnitudes of water and air velocities and their relative proportions.