Computational Fluid Dynamics(CFD)investigations into water entry problems of a rigid flat plate with air pockets were systematically conducted.The Volume of Fluid(VOF)model was utilised to capture localised slamming p...Computational Fluid Dynamics(CFD)investigations into water entry problems of a rigid flat plate with air pockets were systematically conducted.The Volume of Fluid(VOF)model was utilised to capture localised slamming phenomena that occur during,and post-impact events.The model’s geometry was modified to include a pocket on the slamming impact surface to investigate the effect of air entrapment on the magnitude and distribution of slamming forces and pressures.A parametric study was conducted on the geometric parameters of the modelled pocket by altering its area,depth,and volume to exam-ine the response of slamming force and pressure loading under several impact velocities.The numerical results of slamming forces and pressures were in good agreement with experimental drop test measure-ments(with relative error of-6%and 7%for the magnitude of slamming force and pressure,respectively).The numerical results proved that the peak pressure is proportional to the magnitude of impact velocity squared(p maxαv^(2)).展开更多
Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction.However,their fundamental hydrodynamic behaviors,which are ess...Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction.However,their fundamental hydrodynamic behaviors,which are essential for reactor scale-up and design,are still not fully understood.To develop design tools for engineering purposes,much research has been carried out in the area of computationalfluid dynamics(CFD)modeling and simulation of gas-liquidflows.Due to the importance of the bubble behavior,the bubble size distribution must be considered in the CFD models.The population balance model(PBM)is an effective approach to predict the bubble size distribution,and great efforts have been made in recent years to couple the PBM into CFD simulations.This article gives a selective review of the modeling and simulation of bubble column reactors using CFD coupled with PBM.Bubble breakup and coalescence models due to different mechanisms are discussed.It is shown that the CFD-PBM coupled model with proper bubble breakup and coalescence models and interphase force formulations has the ability of predicting the complex hydrodynamics in differentflow regimes and,thus,provides a unified description of both the homo-geneous and heterogeneous regimes.Further study is needed to improve the models of bubble coalescence and breakup,turbulence modification in high gas holdup,and interphase forces of bubble swarms.展开更多
Computationalfluid dynamics(CFD)was used to investigate the hydrodynamic parameters of two internal airlift bioreactors with different configurations.Both had a riser diameter of 0.1 m.The model was used to predict the ...Computationalfluid dynamics(CFD)was used to investigate the hydrodynamic parameters of two internal airlift bioreactors with different configurations.Both had a riser diameter of 0.1 m.The model was used to predict the effect of the reactor geometry on the reactor hydrody-namics.Water was utilized as the continuous phase and air in the form of bubbles was applied as the dispersed phase.A two-phaseflow model provided by the bubblyflow application mode was employed in this project.In the liquid phase,the turbulence can be described using the k-εmodel.Simulated gas holdup and liquid circulation velocity results were compared with experimental data.The predictions of the simulation are in good agreement with the experimental data.展开更多
文摘Computational Fluid Dynamics(CFD)investigations into water entry problems of a rigid flat plate with air pockets were systematically conducted.The Volume of Fluid(VOF)model was utilised to capture localised slamming phenomena that occur during,and post-impact events.The model’s geometry was modified to include a pocket on the slamming impact surface to investigate the effect of air entrapment on the magnitude and distribution of slamming forces and pressures.A parametric study was conducted on the geometric parameters of the modelled pocket by altering its area,depth,and volume to exam-ine the response of slamming force and pressure loading under several impact velocities.The numerical results of slamming forces and pressures were in good agreement with experimental drop test measure-ments(with relative error of-6%and 7%for the magnitude of slamming force and pressure,respectively).The numerical results proved that the peak pressure is proportional to the magnitude of impact velocity squared(p maxαv^(2)).
基金gratefully acknowledged the financial supports by the National Natural Science Foundation of China(Grant No.20606021)Foundation for the Author of National Excellent Doctoral Dissertation of China(No.200757)the State Key Development Program for Basic Research Project of China(Grant No.2007CB714302).
文摘Bubble columns are widely used in chemical and biochemical processes due to their excellent mass and heat transfer characteristics and simple construction.However,their fundamental hydrodynamic behaviors,which are essential for reactor scale-up and design,are still not fully understood.To develop design tools for engineering purposes,much research has been carried out in the area of computationalfluid dynamics(CFD)modeling and simulation of gas-liquidflows.Due to the importance of the bubble behavior,the bubble size distribution must be considered in the CFD models.The population balance model(PBM)is an effective approach to predict the bubble size distribution,and great efforts have been made in recent years to couple the PBM into CFD simulations.This article gives a selective review of the modeling and simulation of bubble column reactors using CFD coupled with PBM.Bubble breakup and coalescence models due to different mechanisms are discussed.It is shown that the CFD-PBM coupled model with proper bubble breakup and coalescence models and interphase force formulations has the ability of predicting the complex hydrodynamics in differentflow regimes and,thus,provides a unified description of both the homo-geneous and heterogeneous regimes.Further study is needed to improve the models of bubble coalescence and breakup,turbulence modification in high gas holdup,and interphase forces of bubble swarms.
文摘Computationalfluid dynamics(CFD)was used to investigate the hydrodynamic parameters of two internal airlift bioreactors with different configurations.Both had a riser diameter of 0.1 m.The model was used to predict the effect of the reactor geometry on the reactor hydrody-namics.Water was utilized as the continuous phase and air in the form of bubbles was applied as the dispersed phase.A two-phaseflow model provided by the bubblyflow application mode was employed in this project.In the liquid phase,the turbulence can be described using the k-εmodel.Simulated gas holdup and liquid circulation velocity results were compared with experimental data.The predictions of the simulation are in good agreement with the experimental data.
