The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vortici...The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vorticity production and transport.The numerical method employs an adaptive unstructured quadrilateral mesh,which can capture the wave pattern and interface evolution very well.Simulations are carried out under the conditions of an incident shock Mach number of 1.2 and the light/heavy (air/SF 6) interface.Five different shapes are considered in the simulations:rectangle,ellipse,diamond and two kinds of triangle.The results show that the interfacial shapes can influence the wave patterns particularly on the shape and evolution of refracted shock waves.The generation and the distribution of vorticity on the interfaces with five different shapes also have dissimilarities.The circulation deposition on five interfaces is quantitatively investigated and compared with theoretical model.A good agreement is found between the numerical results and the predictions by the theoretical model.Some characteristic scales of the interface are tracked.Under the influence of nonlinear-acoustic effect and vorticity effect,the interfaces present different evolution modes.展开更多
The structure and rheological properties of carbon-based particle suspensions, i.e., carbon black（CB）, multi-wall carbon nanotube（MWNT）, graphene and hollow carbon sphere（HCS） suspended in polydimethylsiloxane（...The structure and rheological properties of carbon-based particle suspensions, i.e., carbon black（CB）, multi-wall carbon nanotube（MWNT）, graphene and hollow carbon sphere（HCS） suspended in polydimethylsiloxane（PDMS）, are investigated. In order to study the effect of particle shape on the structure and rheological properties of suspensions, the content of surface oxygen-containing functional groups of carbon-based particles is controlled to be similar. Original spherical-like CB（fractal filler）, rod-like MWNT and sheet-like graphene form large agglomerates in PDMS, while spherical HCS particles disperse relatively well in PDMS. The dispersion state of carbon-based particles affects the critical concentration of forming a rheological percolation network. Under weak shear, negative normal stress differences（ΔN） are observed in CB, MWNT and graphene suspensions, while ΔN is nearly zero for HCS suspensions. It is concluded that the vorticity alignment of CB, MWNT and graphene agglomerates under shear results in the negative ΔN. However, no obvious structural change is observed in HCS suspension under weak shear, and accordingly, the ΔN is almost zero.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.10972214)the Fundamental Research Funds for the Central Universities
文摘The early phases of the shock interaction process on two-dimensional interfaces with different shapes are numerically investigated in this study,which are closely related to the shock refraction and reflection,vorticity production and transport.The numerical method employs an adaptive unstructured quadrilateral mesh,which can capture the wave pattern and interface evolution very well.Simulations are carried out under the conditions of an incident shock Mach number of 1.2 and the light/heavy (air/SF 6) interface.Five different shapes are considered in the simulations:rectangle,ellipse,diamond and two kinds of triangle.The results show that the interfacial shapes can influence the wave patterns particularly on the shape and evolution of refracted shock waves.The generation and the distribution of vorticity on the interfaces with five different shapes also have dissimilarities.The circulation deposition on five interfaces is quantitatively investigated and compared with theoretical model.A good agreement is found between the numerical results and the predictions by the theoretical model.Some characteristic scales of the interface are tracked.Under the influence of nonlinear-acoustic effect and vorticity effect,the interfaces present different evolution modes.
基金financially supported by the National Natural Science Foundation of China(Nos.21474111,21222407 and 21274152)subsidized by the National Basic Research Program of China(973 Program,2012CB821500)
文摘The structure and rheological properties of carbon-based particle suspensions, i.e., carbon black（CB）, multi-wall carbon nanotube（MWNT）, graphene and hollow carbon sphere（HCS） suspended in polydimethylsiloxane（PDMS）, are investigated. In order to study the effect of particle shape on the structure and rheological properties of suspensions, the content of surface oxygen-containing functional groups of carbon-based particles is controlled to be similar. Original spherical-like CB（fractal filler）, rod-like MWNT and sheet-like graphene form large agglomerates in PDMS, while spherical HCS particles disperse relatively well in PDMS. The dispersion state of carbon-based particles affects the critical concentration of forming a rheological percolation network. Under weak shear, negative normal stress differences（ΔN） are observed in CB, MWNT and graphene suspensions, while ΔN is nearly zero for HCS suspensions. It is concluded that the vorticity alignment of CB, MWNT and graphene agglomerates under shear results in the negative ΔN. However, no obvious structural change is observed in HCS suspension under weak shear, and accordingly, the ΔN is almost zero.
