The motion of particles in different channel Brownian pumps can be described by Langevin equations,and the pumping capacity is a useful indicator to demonstrate the strength of a pump’s transportation ability.Via the...The motion of particles in different channel Brownian pumps can be described by Langevin equations,and the pumping capacity is a useful indicator to demonstrate the strength of a pump’s transportation ability.Via the simulation,there is always an optimal value of temperature and unbiased external force for different pumps which make the concentration ratio between the right tube and left tube derive its maximum and minimum in two asymmetric tubes respectively.Besides,the concentration ratio will keep 1 regardless of radius,temperature or magnitude of force in the tube in a symmetric tube.To obtain more information about pumping capacity,exploring the average probability current(APC) of tubes in different conditions is necessary.Results indicate that as the concentration ratio is 1,the change of the APC when x_(0)=0 is similar to that when x_(0)=π.Also,when the concentration ratio is more than 1,there are optimal values of temperature,radius and magnitude of force where the APC gains a maximum,and the maximum decreases as the concentration in the right tube increases when x_(0)=0.展开更多
This work focused on exploring a computational fluid dynamics(CFD)method to predict the macromixing characteristics including the mean flow field and impeller capacity for a 45° down-pumping pitched blade turbine...This work focused on exploring a computational fluid dynamics(CFD)method to predict the macromixing characteristics including the mean flow field and impeller capacity for a 45° down-pumping pitched blade turbine(PBT)in stirred tanks. Firstly, the three typical mean flow fields were investigated by virtue of three components of liquid velocity. Then the effects of impeller diameter(D)and off-bottom clearance(C)on both the mean flow field and three global macro-mixing parameters concerning impeller capacity were studied in detail. The changes of flow patterns with increasing C/D were predicted from these effects. The simulation results are consistent with the experimental results in published literature.展开更多
The flow fields in fully baffled, cylindrical vessels of 250 and 360 mm diameter respectively, with a series of downflow pitched turbines (PTD) and upflow pitched turbines (PTU) have been measured using the two compo...The flow fields in fully baffled, cylindrical vessels of 250 and 360 mm diameter respectively, with a series of downflow pitched turbines (PTD) and upflow pitched turbines (PTU) have been measured using the two component LDA. The flow fields of the PTD and PTU are substantially more complex than the conventional patterns reported previously. Instead of a single circulation loop, the present results show that a primary circulation loop does not reach the bottom of the tank for an impeller clearance of the T/2, but it is accompanied by a secondary circulation loop. However, when the diameter of the impeller decrease from T/2 to T/3, the secondary circulation loop disappear. The distribution of axial pumping capacity is also provided.展开更多
基金National Natural Science Foundation of China (No. 61975058)Blue Shield Technology Project,China (No. LD20170209)。
文摘The motion of particles in different channel Brownian pumps can be described by Langevin equations,and the pumping capacity is a useful indicator to demonstrate the strength of a pump’s transportation ability.Via the simulation,there is always an optimal value of temperature and unbiased external force for different pumps which make the concentration ratio between the right tube and left tube derive its maximum and minimum in two asymmetric tubes respectively.Besides,the concentration ratio will keep 1 regardless of radius,temperature or magnitude of force in the tube in a symmetric tube.To obtain more information about pumping capacity,exploring the average probability current(APC) of tubes in different conditions is necessary.Results indicate that as the concentration ratio is 1,the change of the APC when x_(0)=0 is similar to that when x_(0)=π.Also,when the concentration ratio is more than 1,there are optimal values of temperature,radius and magnitude of force where the APC gains a maximum,and the maximum decreases as the concentration in the right tube increases when x_(0)=0.
文摘This work focused on exploring a computational fluid dynamics(CFD)method to predict the macromixing characteristics including the mean flow field and impeller capacity for a 45° down-pumping pitched blade turbine(PBT)in stirred tanks. Firstly, the three typical mean flow fields were investigated by virtue of three components of liquid velocity. Then the effects of impeller diameter(D)and off-bottom clearance(C)on both the mean flow field and three global macro-mixing parameters concerning impeller capacity were studied in detail. The changes of flow patterns with increasing C/D were predicted from these effects. The simulation results are consistent with the experimental results in published literature.
文摘The flow fields in fully baffled, cylindrical vessels of 250 and 360 mm diameter respectively, with a series of downflow pitched turbines (PTD) and upflow pitched turbines (PTU) have been measured using the two component LDA. The flow fields of the PTD and PTU are substantially more complex than the conventional patterns reported previously. Instead of a single circulation loop, the present results show that a primary circulation loop does not reach the bottom of the tank for an impeller clearance of the T/2, but it is accompanied by a secondary circulation loop. However, when the diameter of the impeller decrease from T/2 to T/3, the secondary circulation loop disappear. The distribution of axial pumping capacity is also provided.
