Flow of two immiscible fluids gives rise to variety of flow patterns,which influence transportation process.In this work,we present detailed analysis on the prediction of flow pattern maps and radial distribution of v...Flow of two immiscible fluids gives rise to variety of flow patterns,which influence transportation process.In this work,we present detailed analysis on the prediction of flow pattern maps and radial distribution of volume fraction,pressure and velocity of a pair of immiscible liquids through a horizontal pipeline by computational fluid dynamics（CFD） simulation using ANSYS FLUENT 6.3.Moderately viscous oil and water have been taken as the fluid pair for study.Volume of fluid（VOF） method has been employed to predict various flow patterns by assuming unsteady flow,immiscible liquid pair,constant liquid properties,and co-axial flow.From the grid independent study,we have selected 47 037 number of quadrilateral mesh elements for the entire geometry.Simulation successfully predicts almost all the flow patterns（viz.,plug,slug,stratified wavy,stratified mixed and annular）,except dispersion of oil in water and dispersion of water in oil.The simulated results are validated with experimental results of oil volume fraction and flow pattern map.Radial distribution of volume fraction,pressure and velocity profiles describe the nature of the stratified wavy,stratified mixed and annular flow pattern.These profiles help to developing the phenomenological correlations of interfacial characteristics in two-phase flow.展开更多
Numerical approach of hybrid laminar flow control （HLFC） is investigated for the suc- tion hole with a width between 0.5 mm and 7 mm. The accuracy of Menter and Langtry＇s transition model applied for simulating the...Numerical approach of hybrid laminar flow control （HLFC） is investigated for the suc- tion hole with a width between 0.5 mm and 7 mm. The accuracy of Menter and Langtry＇s transition model applied for simulating the flow with boundary layer suction is validated. The experiment data are compared with the computational results. The solutions show that this transition model can pre- dict the transition position with suction control accurately. A well designed laminar airfoil is selected in the present research. For suction control with a single hole, the physical mechanism of suction control, including the impact of suction coefficient and the width and position of the suc- tion hole on control results, is analyzed. The single hole simulation results indicate that it is favor- able for transition delay and drag reduction to increase the suction coefficient and set the hole position closer to the trailing edge properly. The modified radial basis function （RBF） neural net- work and the modified differential evolution algorithm are used to optimize the design for suction control with three holes. The design variables are suction coefficient, hole width, hole position and hole spacing. The optimization target is to obtain the minimum drag coefficient. After optimization, the transition delay can be up to 17% and the aerodynamic drag coefficient can decrease by 12.1%.展开更多
文摘Flow of two immiscible fluids gives rise to variety of flow patterns,which influence transportation process.In this work,we present detailed analysis on the prediction of flow pattern maps and radial distribution of volume fraction,pressure and velocity of a pair of immiscible liquids through a horizontal pipeline by computational fluid dynamics（CFD） simulation using ANSYS FLUENT 6.3.Moderately viscous oil and water have been taken as the fluid pair for study.Volume of fluid（VOF） method has been employed to predict various flow patterns by assuming unsteady flow,immiscible liquid pair,constant liquid properties,and co-axial flow.From the grid independent study,we have selected 47 037 number of quadrilateral mesh elements for the entire geometry.Simulation successfully predicts almost all the flow patterns（viz.,plug,slug,stratified wavy,stratified mixed and annular）,except dispersion of oil in water and dispersion of water in oil.The simulated results are validated with experimental results of oil volume fraction and flow pattern map.Radial distribution of volume fraction,pressure and velocity profiles describe the nature of the stratified wavy,stratified mixed and annular flow pattern.These profiles help to developing the phenomenological correlations of interfacial characteristics in two-phase flow.
基金supported by the National Basic Research Program of China (No. 2014CB744804)
文摘Numerical approach of hybrid laminar flow control （HLFC） is investigated for the suc- tion hole with a width between 0.5 mm and 7 mm. The accuracy of Menter and Langtry＇s transition model applied for simulating the flow with boundary layer suction is validated. The experiment data are compared with the computational results. The solutions show that this transition model can pre- dict the transition position with suction control accurately. A well designed laminar airfoil is selected in the present research. For suction control with a single hole, the physical mechanism of suction control, including the impact of suction coefficient and the width and position of the suc- tion hole on control results, is analyzed. The single hole simulation results indicate that it is favor- able for transition delay and drag reduction to increase the suction coefficient and set the hole position closer to the trailing edge properly. The modified radial basis function （RBF） neural net- work and the modified differential evolution algorithm are used to optimize the design for suction control with three holes. The design variables are suction coefficient, hole width, hole position and hole spacing. The optimization target is to obtain the minimum drag coefficient. After optimization, the transition delay can be up to 17% and the aerodynamic drag coefficient can decrease by 12.1%.
