Porous particle flow is universal in nature and industry.However,in previous numerical simulations,porous particles have usually been assumed to be solid.It is necessary to study the flow and heat-transfer characteris...Porous particle flow is universal in nature and industry.However,in previous numerical simulations,porous particles have usually been assumed to be solid.It is necessary to study the flow and heat-transfer characteristics around porous particles because they are greatly different from those of impermeable particles.In this study,two-dimensional steady flow and heat transfer around and through a porous particle with a constant temperature placed in a cold fluid were numerically investigated.The effects of the Reynolds number(Re)and Darcy number(Da)on the flow and heat-transfer characteristics were investigated in detail.The investigated ranges of the parameters were 10≤Re≤40 and 10^(−6)≤Da≤10^(−2).It is sophisticated to simulate porous particles with traditional simulation methods because of their complicated structure.Therefore,the lattice Boltzmann method was used to solve the generalized macroscopic governing equations because of its simplicity.The drag coefficient decreased with increasing Re or Da,but the decrease was not prominent in the range 10^(−6)≤Da≤10^(−4).The heat-transfer efficiency of the front surface was much stronger than that of the rear surface.The heat-transfer efficiency between the particle and the fluid increased with increasing Re or Da.However,for 10^(−6)≤Da≤10^(−4),the increase was not prominent and the heat-transfer enhancement ratio was slightly larger than one.Furthermore,the effect of Da became more prominent at larger Re.In addition,new correlations for the drag coefficient and surface-averaged Nusselt number were obtained based on the simulated results.展开更多
The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins.In recent decades,researchers have identified glacier acceleration along Antarc...The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins.In recent decades,researchers have identified glacier acceleration along Antarctic ice sheet coastal margins.However,the study of ice sheet interiors where seasonal accumulation eventually balances ice wastage at the lower elevation is poorly understood.In this paper,the ice sheet elevation change around Dome A region is analyzed from 2002 to 2012 using two million elevation change measurements from EnviSat satellite radar altimeter data covering an area of about 7000 km2.A declining trend of 0.572±1.31 mm/year which means that the Dome A region was in balance during the last decade can be captured.In addition,two obvious changes in accumulation which divide elevation change time series into three independent equilibration stages are also extracted.In order to explain this phenomenon,two speculations related to snowfall and firn compaction are proposed in this paper.展开更多
基金supported by the National Natural Science Foundation of China(grant No.51922086).
文摘Porous particle flow is universal in nature and industry.However,in previous numerical simulations,porous particles have usually been assumed to be solid.It is necessary to study the flow and heat-transfer characteristics around porous particles because they are greatly different from those of impermeable particles.In this study,two-dimensional steady flow and heat transfer around and through a porous particle with a constant temperature placed in a cold fluid were numerically investigated.The effects of the Reynolds number(Re)and Darcy number(Da)on the flow and heat-transfer characteristics were investigated in detail.The investigated ranges of the parameters were 10≤Re≤40 and 10^(−6)≤Da≤10^(−2).It is sophisticated to simulate porous particles with traditional simulation methods because of their complicated structure.Therefore,the lattice Boltzmann method was used to solve the generalized macroscopic governing equations because of its simplicity.The drag coefficient decreased with increasing Re or Da,but the decrease was not prominent in the range 10^(−6)≤Da≤10^(−4).The heat-transfer efficiency of the front surface was much stronger than that of the rear surface.The heat-transfer efficiency between the particle and the fluid increased with increasing Re or Da.However,for 10^(−6)≤Da≤10^(−4),the increase was not prominent and the heat-transfer enhancement ratio was slightly larger than one.Furthermore,the effect of Da became more prominent at larger Re.In addition,new correlations for the drag coefficient and surface-averaged Nusselt number were obtained based on the simulated results.
基金This work was supported by the Chinese Polar Environment Comprehensive Investigation and Assessment Programmes[grant number CHINARE2015–02-04]the Public Science and Technology Research Fund Project of Surveying,Mapping and Geoinformation[grant number 201412009]+2 种基金the National Nature Science Foundation of China[grant number 41376187]the Polar Strategic Foundation[grant number 20120107]the Advance Research Program of Civil Aerospace Technology[grant number D040103].
文摘The expected responses of ice sheets to climate warming are growth in the thickness of the inland ice areas and thinning near the margins.In recent decades,researchers have identified glacier acceleration along Antarctic ice sheet coastal margins.However,the study of ice sheet interiors where seasonal accumulation eventually balances ice wastage at the lower elevation is poorly understood.In this paper,the ice sheet elevation change around Dome A region is analyzed from 2002 to 2012 using two million elevation change measurements from EnviSat satellite radar altimeter data covering an area of about 7000 km2.A declining trend of 0.572±1.31 mm/year which means that the Dome A region was in balance during the last decade can be captured.In addition,two obvious changes in accumulation which divide elevation change time series into three independent equilibration stages are also extracted.In order to explain this phenomenon,two speculations related to snowfall and firn compaction are proposed in this paper.
