High speed microphotographic studies showed that fluid elements injected from a point source tended to exhibit slice-like and strip-like configurations rather than lamellar structure during the turbulent mixing of flu...High speed microphotographic studies showed that fluid elements injected from a point source tended to exhibit slice-like and strip-like configurations rather than lamellar structure during the turbulent mixing of fluids with Sc〉〉1 . Based on this phenomenon a new micromixing model was developed. The model stated that micromixing was contributed by shrinkage deformation and molecular diffusion on a slab element surrounded by an infinite ambient fluid. Balance between the deformation and the diffusion resulted in an exponential increase in volume for the element. After a certain period of time tm , the volumetric increase of the feed material would be confined by the development and extension of the turbulent spreading zone. Therefore, three successive downstream regions, with different controlling steps and segregation states, could be recognized. A simplified picture for the point source mixing was then drawn, which might serve as a basis for describing chemical reactions during turbulent mixing.展开更多
Macro and micromixing time represent two extreme mixing time scales,which governs the whole hydrodynamics characteristics of the surface aeration systems.With the help of experimental and numerical analysis,simulation...Macro and micromixing time represent two extreme mixing time scales,which governs the whole hydrodynamics characteristics of the surface aeration systems.With the help of experimental and numerical analysis,simulation equation governing those times scale has been presented in the present work.展开更多
An integral description of chemical reactions taken place under mixing was formulated on the basis of the three-region model pictured in Part Ⅰ of this study. A mathematically simplified version of the model was deve...An integral description of chemical reactions taken place under mixing was formulated on the basis of the three-region model pictured in Part Ⅰ of this study. A mathematically simplified version of the model was developed. It was shown that the converted portion of the material in the dispersion region can be neglected provided that the initial concentration ratio of A and B was less than 0.1, and the effects of micro - and macromixing on the chemical reactions could be represented by two dimensionless numbers: Dα and Π. The model was applied to two reacting systems: competitive-consecutive reactions and parallel reactions. Agreement between model prediction and experimental results demonstrated that the present framework, though in simplified form, is capable of describing reactive mixing without loss of any significant features of the process.展开更多
基金Supported by the National Natural Science Foundation of China and China Petrochemical Corporation.
文摘High speed microphotographic studies showed that fluid elements injected from a point source tended to exhibit slice-like and strip-like configurations rather than lamellar structure during the turbulent mixing of fluids with Sc〉〉1 . Based on this phenomenon a new micromixing model was developed. The model stated that micromixing was contributed by shrinkage deformation and molecular diffusion on a slab element surrounded by an infinite ambient fluid. Balance between the deformation and the diffusion resulted in an exponential increase in volume for the element. After a certain period of time tm , the volumetric increase of the feed material would be confined by the development and extension of the turbulent spreading zone. Therefore, three successive downstream regions, with different controlling steps and segregation states, could be recognized. A simplified picture for the point source mixing was then drawn, which might serve as a basis for describing chemical reactions during turbulent mixing.
基金Supported by the Department of Science and Technology,Government of India (DSTO717)
文摘Macro and micromixing time represent two extreme mixing time scales,which governs the whole hydrodynamics characteristics of the surface aeration systems.With the help of experimental and numerical analysis,simulation equation governing those times scale has been presented in the present work.
基金Supported by the National Natural Science Foundation of China and China Petrochemical Corporation.
文摘An integral description of chemical reactions taken place under mixing was formulated on the basis of the three-region model pictured in Part Ⅰ of this study. A mathematically simplified version of the model was developed. It was shown that the converted portion of the material in the dispersion region can be neglected provided that the initial concentration ratio of A and B was less than 0.1, and the effects of micro - and macromixing on the chemical reactions could be represented by two dimensionless numbers: Dα and Π. The model was applied to two reacting systems: competitive-consecutive reactions and parallel reactions. Agreement between model prediction and experimental results demonstrated that the present framework, though in simplified form, is capable of describing reactive mixing without loss of any significant features of the process.
