Motivated by the recent biomimic design of microstructured adhesive surfaces,we study adhesion between a film-terminated fibrillar array and a rigid substrate.Using a two-dimensional model and ignoring the deformation...Motivated by the recent biomimic design of microstructured adhesive surfaces,we study adhesion between a film-terminated fibrillar array and a rigid substrate.Using a two-dimensional model and ignoring the deformation of the fibers and the backing layer,we show that the adhesion behavior is dominated by a dimensionless parameter reflecting the global flexibility of the terminal film.In particular,if the parameter is larger than 0.4,the adhesion is reversible;otherwise one or more hysteresis loops will appear after an approach-retraction cycle,leading to significant increase in the specific separation work.The result is expected to help not only optimal design of the structure,but also other applications such as micro-manipulation in micromechanical systems.展开更多
A topology method is presented in this paper to reveal flow structure occurring inside turbomachinery,in which near wall now structure is revealed by using wall limiting streamlines and space flow feature is revealed ...A topology method is presented in this paper to reveal flow structure occurring inside turbomachinery,in which near wall now structure is revealed by using wall limiting streamlines and space flow feature is revealed by using space streamlines and cross-section streamlines. As an example, a computational three-dimensional viscous flow field inside a transonic turbine cascade is studied. Through the analysis,the form and evolution of vortex system and the whole process of separation occurring within this cascade are revealed. The application of topology method for analyze fiow structure inside turbomachinery is very important for understanding flow features and mechanism of flow loss even for improving the design of turbomachinery and increasing its efficiency.展开更多
基金supported by the National Basic Research Program of China (Grant No. 2011CB302101)PhD Programs Foundation of the Ministry of Education of China (Grant No. 20113402110005)
文摘Motivated by the recent biomimic design of microstructured adhesive surfaces,we study adhesion between a film-terminated fibrillar array and a rigid substrate.Using a two-dimensional model and ignoring the deformation of the fibers and the backing layer,we show that the adhesion behavior is dominated by a dimensionless parameter reflecting the global flexibility of the terminal film.In particular,if the parameter is larger than 0.4,the adhesion is reversible;otherwise one or more hysteresis loops will appear after an approach-retraction cycle,leading to significant increase in the specific separation work.The result is expected to help not only optimal design of the structure,but also other applications such as micro-manipulation in micromechanical systems.
文摘A topology method is presented in this paper to reveal flow structure occurring inside turbomachinery,in which near wall now structure is revealed by using wall limiting streamlines and space flow feature is revealed by using space streamlines and cross-section streamlines. As an example, a computational three-dimensional viscous flow field inside a transonic turbine cascade is studied. Through the analysis,the form and evolution of vortex system and the whole process of separation occurring within this cascade are revealed. The application of topology method for analyze fiow structure inside turbomachinery is very important for understanding flow features and mechanism of flow loss even for improving the design of turbomachinery and increasing its efficiency.
