In the present article, velocity and deformation of an air bubble have been considered in quiescent liquid at different consecutive slopes from 5 to 90 degrees in respect to horizontal condition. To establish these purposes, air-water two-phase flow has been simulated numerically by using volume of fluid method. The two-phase flow interface has been traced by using Piecewise Linear Interface Calculation (PLIC) method. Surface tension force was estimated by Continuum Surface Force (CSF) model. The simulation results show that maximum bubble velocity occurred at 45 degrees which is in agreement with the previous researchers result. Simulation of bubble movement was also continued to two consecutive slopes at different angles. At slope deviation location, a vortex was generated due to liquid movement governed by gravity forces. This vortex changes the bubble velocity as well as bubble shape. This vortex also reduces the bubble velocity and changes the bubble nose shape from sharp to flatten at deviation from low to high slope values. However, at deviations from high to low slope values, the bubble nose becomes more sharpened in addition to bubble velocity increase. The maximum average velocity of bubble movement at two consecutive slopes was obtained during the condition that the first and second slopes were set to 60 and 30 degrees, respectively.

Keywords: Numerical simulation, Bubble, Inclined channel, VOF method

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