A numerical study of the parameters controlling the viscous penalty method is investigated to better set up Particle-Resolved Direct Numerical Simulations (PR-DNS) of particulate flows. Based on this analysis, improve...A numerical study of the parameters controlling the viscous penalty method is investigated to better set up Particle-Resolved Direct Numerical Simulations (PR-DNS) of particulate flows. Based on this analysis, improvements of the methods are proposed in order to reach an almost second order convergence in space. The viscous penalty method is validated in Stokes regime by simulating a uniform flow past a fixed isolated cylinder. Moreover, it is also utilized in moderate Reynolds number regime for a uniform flow past a square configuration of cylinder and compared in terms of friction factor to the well-known Ergun correlation.展开更多
During the solidification of a sessile drop,the effect of heat exchange from the gaseous environmental medium is generally ignored.However,by combining experimental observations,direct numerical simulations,and a theo...During the solidification of a sessile drop,the effect of heat exchange from the gaseous environmental medium is generally ignored.However,by combining experimental observations,direct numerical simulations,and a theoretical model,we have demonstrated that the environmental medium,particularly one with high thermal conductivity such as a liquid,has nonnegligible heat exchange with both the drop and the substrate,leading to accelerated cooling of the outer surface of the sessile drop.Consequently,it causes alterations in the geometry of the freezing front and ultimately results in the formation of a solidified shell that encloses the drop.Furthermore,the encapsulated liquid continues to solidify,which induces volume change and consequently changes the final outcome of the freezing process.This study highlights the importance of considering the properties of the environmental medium and provides novel strategies to manipulate the freezing rate and reshape the morphology of the solidified drop.展开更多
文摘A numerical study of the parameters controlling the viscous penalty method is investigated to better set up Particle-Resolved Direct Numerical Simulations (PR-DNS) of particulate flows. Based on this analysis, improvements of the methods are proposed in order to reach an almost second order convergence in space. The viscous penalty method is validated in Stokes regime by simulating a uniform flow past a fixed isolated cylinder. Moreover, it is also utilized in moderate Reynolds number regime for a uniform flow past a square configuration of cylinder and compared in terms of friction factor to the well-known Ergun correlation.
基金Natural Science Foundation of China,Grant/Award Numbers:11988102,91852202,11861131005New Cornerstone Science FoundationChina Postdoctoral Science Foundation,Grant/Award Numbers:2022T150068,2021M700507。
文摘During the solidification of a sessile drop,the effect of heat exchange from the gaseous environmental medium is generally ignored.However,by combining experimental observations,direct numerical simulations,and a theoretical model,we have demonstrated that the environmental medium,particularly one with high thermal conductivity such as a liquid,has nonnegligible heat exchange with both the drop and the substrate,leading to accelerated cooling of the outer surface of the sessile drop.Consequently,it causes alterations in the geometry of the freezing front and ultimately results in the formation of a solidified shell that encloses the drop.Furthermore,the encapsulated liquid continues to solidify,which induces volume change and consequently changes the final outcome of the freezing process.This study highlights the importance of considering the properties of the environmental medium and provides novel strategies to manipulate the freezing rate and reshape the morphology of the solidified drop.
