Within the framework of the Navier–Stokes equations,the Weissenberg effect of turbulence is investigated.We begin with our investigation on the elastic effect of homogeneous turbulent shear flow.First,in the sense of...Within the framework of the Navier–Stokes equations,the Weissenberg effect of turbulence is investigated.We begin with our investigation on the elastic effect of homogeneous turbulent shear flow.First,in the sense of Truesdell(Physics of Fluids,1964)on the natural time of materials,we derive the natural time of turbulence,and use it together with the natural viscosity of turbulence derived in the article of Huang et al.(Journal of Turbulence,2003)to define the natural Weissenberg number of turbulence as a measure of the elastic effect of homogeneous turbulence.Second,we define a primary Weissenberg number of turbulence,which in laminar flow reduces to the Weissenberg number widely applied in rheology to characterize the elasticity of visco-elastic fluids.Our analysis based on the experimental results of Tavoularis and Karnik(Journal of Fluid Mechanics,1989)indicates that the larger is the Weissenberg number of turbulence,the more elastic becomes the turbulent flow concerned.Furthermore,we put forth a general Weissenberg number of turbulence,which includes the primary Weissenberg number of turbulence as a special case,to measure the overall elastic effects of turbulence.Besides,it is shown that the general Weissenberg number can also be used to characterize the elastic effects of non-Newtonian fluids in laminar flow.展开更多
According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of...According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio.This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied.The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.展开更多
We present a comprehensive workflow to obtain the best insights into the viscoelastic behavior of polymers. Viscoelasticity is depicted in most cases by the current commercially available polymers used for EOR applica...We present a comprehensive workflow to obtain the best insights into the viscoelastic behavior of polymers. Viscoelasticity is depicted in most cases by the current commercially available polymers used for EOR applications. The phenomenon is debated to be one of the reasons for additional oil recovery during polymer flooding applications. It is somehow accepted that polymer increases volumetric sweep efficiency owing to improved mobility ratio. Recently researches have explained that flooding polymers in porous media with elastic characteristics could recover additional oil, due to the improved microscale oil displacement (pore-scale). This study focuses on the analysis of polymer viscoelasticity based on single-phase core, sand-pack and capillary tube (CT) experiments coupled with their detailed rheological characterization, in order to evaluate polymer behavior in porous media. A combination of hydrolyzed polyacrylamides (HPAM) polymers as well as a bio polymer is presented throughout this evaluation. The evaluation of the data is addressed on the basis of pressure drop across the pores, separating the shear associated pressure by the extensional thickening associated pressure. Apart from that, viscoelastic dependence of the converging-diverging geometry has been experimented. Based on the observed behavior through porous media, HPAM polymers are compared with bio polymers. Moreover, the behavior of solutions with induced mechanical degradation (pre-sheared) is compared with non-sheared solutions. Similarly, concentrations with different polymer solutions are evaluated. The results obtained in this work allow for additional understanding of polymer solutions behavior in flooding applications. Furthermore?The results support?the definition of optimized workflows to assess their behavior under flow through porous media. Finally this evaluation helps to describe the parameter that defines polymer viscoelastic properties.展开更多
文摘Within the framework of the Navier–Stokes equations,the Weissenberg effect of turbulence is investigated.We begin with our investigation on the elastic effect of homogeneous turbulent shear flow.First,in the sense of Truesdell(Physics of Fluids,1964)on the natural time of materials,we derive the natural time of turbulence,and use it together with the natural viscosity of turbulence derived in the article of Huang et al.(Journal of Turbulence,2003)to define the natural Weissenberg number of turbulence as a measure of the elastic effect of homogeneous turbulence.Second,we define a primary Weissenberg number of turbulence,which in laminar flow reduces to the Weissenberg number widely applied in rheology to characterize the elasticity of visco-elastic fluids.Our analysis based on the experimental results of Tavoularis and Karnik(Journal of Fluid Mechanics,1989)indicates that the larger is the Weissenberg number of turbulence,the more elastic becomes the turbulent flow concerned.Furthermore,we put forth a general Weissenberg number of turbulence,which includes the primary Weissenberg number of turbulence as a special case,to measure the overall elastic effects of turbulence.Besides,it is shown that the general Weissenberg number can also be used to characterize the elastic effects of non-Newtonian fluids in laminar flow.
基金supported by the National Natural Science Foundation of China (Grant No.40671026)
文摘According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio.This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied.The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.
文摘We present a comprehensive workflow to obtain the best insights into the viscoelastic behavior of polymers. Viscoelasticity is depicted in most cases by the current commercially available polymers used for EOR applications. The phenomenon is debated to be one of the reasons for additional oil recovery during polymer flooding applications. It is somehow accepted that polymer increases volumetric sweep efficiency owing to improved mobility ratio. Recently researches have explained that flooding polymers in porous media with elastic characteristics could recover additional oil, due to the improved microscale oil displacement (pore-scale). This study focuses on the analysis of polymer viscoelasticity based on single-phase core, sand-pack and capillary tube (CT) experiments coupled with their detailed rheological characterization, in order to evaluate polymer behavior in porous media. A combination of hydrolyzed polyacrylamides (HPAM) polymers as well as a bio polymer is presented throughout this evaluation. The evaluation of the data is addressed on the basis of pressure drop across the pores, separating the shear associated pressure by the extensional thickening associated pressure. Apart from that, viscoelastic dependence of the converging-diverging geometry has been experimented. Based on the observed behavior through porous media, HPAM polymers are compared with bio polymers. Moreover, the behavior of solutions with induced mechanical degradation (pre-sheared) is compared with non-sheared solutions. Similarly, concentrations with different polymer solutions are evaluated. The results obtained in this work allow for additional understanding of polymer solutions behavior in flooding applications. Furthermore?The results support?the definition of optimized workflows to assess their behavior under flow through porous media. Finally this evaluation helps to describe the parameter that defines polymer viscoelastic properties.
