The typical black storms or sand-dust storms in the northwestern China are generated and developed through an interaction between the specific large scale circulation pattern and mesoseale systems.The passing by/over ...The typical black storms or sand-dust storms in the northwestern China are generated and developed through an interaction between the specific large scale circulation pattern and mesoseale systems.The passing by/over a huge sand-abundant desert of a strong cold front with intensive frontal zone at mid and lower levels is a necessary condition for the formation and development of a black storm or a severe sand-dust storm.In order to investigate the mechanism of the sand-dust mobilization,transport and sedimentation during the black or sand-dust storms,a parameterization scheme of sand-dust source-sink terms and an equation of transport for the sand-dust were proposed and incorporated into the MM4 mesoscale model.The modified MM4 model was applied to the“May 1993”black storm case and succeeded in reproducing the evolution of the weather systems associated with the black-storm,the sand-dust concentration at surface layer and its vertical distribution,and the sand-dust sedimentation and transport.Our results show that the numerical simulating method by using a mesoscale model,with inclusion of an equation of the sand-dust transport and a parameterization scheme of the sand-dust source-sink terms,is a promising approach to study the mechanism for sand-dust mobilization,transport and sedimentation during a sand-dust storm event.展开更多
A computational fluid dynamics( CFD) model was presented to simulate wind flow over a forest canopy for analyzing the wind flow within and above forest canopies. Unlike previous studies on the canopy flow,the effect o...A computational fluid dynamics( CFD) model was presented to simulate wind flow over a forest canopy for analyzing the wind flow within and above forest canopies. Unlike previous studies on the canopy flow,the effect of canopy contour on the canopy was considered to develop the simulation method into a more general but complex case of wind flow over a forest canopy,using cedrus deodara and cinnamomum camphora. The desire of this work is mainly motivated to provide a rational way for predicting the wind flow within and above vegetation canopies. The model of canopy is not incorporated in the geometrical model,and it uses a porous domain combined with k-ε two-equation turbulence model with source / sink terms. The objectives of this paper are to analyze the contour of pressure and velocity and compare the simulation results with other works and field measurements. Results are encouraging,as the model profiles of mean velocity( u) qualitatively agree well with other works compared with and quantitatively have similar explanations as several authors. In conclusion, it is demonstrated that the adoption turbulence model with source / sink terms for forest canopies is proved to be a physically accurate and numerically robust method. The model and method are recommended for future use in simulating turbulent flows in forest canopies.展开更多
基金This study was supported by the National Natural Science Foundation of China under grant 49475268
文摘The typical black storms or sand-dust storms in the northwestern China are generated and developed through an interaction between the specific large scale circulation pattern and mesoseale systems.The passing by/over a huge sand-abundant desert of a strong cold front with intensive frontal zone at mid and lower levels is a necessary condition for the formation and development of a black storm or a severe sand-dust storm.In order to investigate the mechanism of the sand-dust mobilization,transport and sedimentation during the black or sand-dust storms,a parameterization scheme of sand-dust source-sink terms and an equation of transport for the sand-dust were proposed and incorporated into the MM4 mesoscale model.The modified MM4 model was applied to the“May 1993”black storm case and succeeded in reproducing the evolution of the weather systems associated with the black-storm,the sand-dust concentration at surface layer and its vertical distribution,and the sand-dust sedimentation and transport.Our results show that the numerical simulating method by using a mesoscale model,with inclusion of an equation of the sand-dust transport and a parameterization scheme of the sand-dust source-sink terms,is a promising approach to study the mechanism for sand-dust mobilization,transport and sedimentation during a sand-dust storm event.
基金National Natural Science Foundations of China(Nos.51178094,41371445)
文摘A computational fluid dynamics( CFD) model was presented to simulate wind flow over a forest canopy for analyzing the wind flow within and above forest canopies. Unlike previous studies on the canopy flow,the effect of canopy contour on the canopy was considered to develop the simulation method into a more general but complex case of wind flow over a forest canopy,using cedrus deodara and cinnamomum camphora. The desire of this work is mainly motivated to provide a rational way for predicting the wind flow within and above vegetation canopies. The model of canopy is not incorporated in the geometrical model,and it uses a porous domain combined with k-ε two-equation turbulence model with source / sink terms. The objectives of this paper are to analyze the contour of pressure and velocity and compare the simulation results with other works and field measurements. Results are encouraging,as the model profiles of mean velocity( u) qualitatively agree well with other works compared with and quantitatively have similar explanations as several authors. In conclusion, it is demonstrated that the adoption turbulence model with source / sink terms for forest canopies is proved to be a physically accurate and numerically robust method. The model and method are recommended for future use in simulating turbulent flows in forest canopies.
