Numerical simulation of flow past circular duct

On the basis of Fluent software, Renormalization Group (RNG)k-ε turbulent model and Volume of Fluid (VOF) method are employed to simulate the flow past circular duct to obtain and analyze the hydraulic parameters. According to various upper and bottom gap-ratios, the force on duct is calculated. Firstly, when bottom gap-ratio is 0, drag force coefficient, lift force coefficient and composite force reach the maximum respectively and azimuth reaches the minimum. Secondly, with the increase of bottom gap-ratio from 0 to 1, drag force coefficient and composite force decrease sharply, lift force coefficient decreases a little, but azimuth increases dramatically. Thirdly, with the continuous increase of bottom gap-ratio from 1, drag force coefficient, lift force coefficient, composite force and azimuth vary little. So, bottom gap-ratio is the key factor influencing the force on circular duct. When bottom gap-ratio is less than 1, upper gap-ratio has the remarkable influence on the circular duct force. When bottom gap-ratio is greater than 1, the varation of upper gap-ratio has a little influence on the circular duct force.