The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical modal, which is developed to model the particle-fluid two-phase flow. The Eule...The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical modal, which is developed to model the particle-fluid two-phase flow. The Eulerian method with the modified k- ε parameterization of turbulence for the fluid phase is used to solve fluid phase, while a Lagrangian method for the sohd phase （particles）, both the processes are coupled through the momentmn sources. In the model the wake turbulence induced by particles has been included as additional source term in the k - ε model; and the variable drift velocities of the particles are treated efficiently by the Lagrangian method in which the particles are tracked explicitly and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumping a cloud of particles is governed by the total buoyancy of the cloud, the drag force on each particle and the velocity of cross-flow. The computed results show a roughly linear relationship between the displacement of the frontal position and the longitudi- nal width of the particle cloud. The particle size in the cloud and the velocity of cross flow dominate the flow behavior. The computed results are compared with the results of laboratory experiments and satisfactory agreement is obtained.展开更多
A series of extensive laboratory experiments were conducted to investigate the transport and mixing of instantaneous discharge of unsorted particle cloud in cross-flow. The following experimental results were obtained...A series of extensive laboratory experiments were conducted to investigate the transport and mixing of instantaneous discharge of unsorted particle cloud in cross-flow. The following experimental results were obtained： （1） the vertical frontal position and the longitudinal width of the particle cloud in the cross-flow is much larger than those in stagnant water, （2） the smaller cross-flow velocity will normally cause the larger non-dimensional frontal position for the same particle size range and initial volume, （3） the non-dimensional longitudinal width of the particle cloud in the cross-flow increases with the increase of cross-flow velocity. The empirical constants （α1, α3 and α2） and their variance range, which can be used to determine the relationships of non-dimensional vertical frontal position and time, longitudinal width and time, and vertical frontal position and longitudinal width were also obtained through the analysis of experimental data.展开更多
基金This work was supported by a grant fromthe Research Grant Council of the Hong Kong Special Administrative Region(Project No5033/98E)
文摘The mixing characteristics of particles such as dredged sediment of variable size discharged into cross flow are studied by a 3D numerical modal, which is developed to model the particle-fluid two-phase flow. The Eulerian method with the modified k- ε parameterization of turbulence for the fluid phase is used to solve fluid phase, while a Lagrangian method for the sohd phase （particles）, both the processes are coupled through the momentmn sources. In the model the wake turbulence induced by particles has been included as additional source term in the k - ε model; and the variable drift velocities of the particles are treated efficiently by the Lagrangian method in which the particles are tracked explicitly and the diffusion process is approximated by a random walk model. The hydrodynamic behavior of dumping a cloud of particles is governed by the total buoyancy of the cloud, the drag force on each particle and the velocity of cross-flow. The computed results show a roughly linear relationship between the displacement of the frontal position and the longitudi- nal width of the particle cloud. The particle size in the cloud and the velocity of cross flow dominate the flow behavior. The computed results are compared with the results of laboratory experiments and satisfactory agreement is obtained.
基金the Key Subject of Shanghai Education Committee (Grant No. J50702).
文摘A series of extensive laboratory experiments were conducted to investigate the transport and mixing of instantaneous discharge of unsorted particle cloud in cross-flow. The following experimental results were obtained： （1） the vertical frontal position and the longitudinal width of the particle cloud in the cross-flow is much larger than those in stagnant water, （2） the smaller cross-flow velocity will normally cause the larger non-dimensional frontal position for the same particle size range and initial volume, （3） the non-dimensional longitudinal width of the particle cloud in the cross-flow increases with the increase of cross-flow velocity. The empirical constants （α1, α3 and α2） and their variance range, which can be used to determine the relationships of non-dimensional vertical frontal position and time, longitudinal width and time, and vertical frontal position and longitudinal width were also obtained through the analysis of experimental data.
