Biomimetic design has recently received widespread attention.Inspired by the Terebridae structure,this paper provides a structural form for suppressing vortex-induced vibration(VIV)response.Four different structural f...Biomimetic design has recently received widespread attention.Inspired by the Terebridae structure,this paper provides a structural form for suppressing vortex-induced vibration(VIV)response.Four different structural forms are shown,including the traditional smooth cylinder(P0),and the Terebridae-inspired cylinder with the helical angle of 30°(P_(30)),60°(P_(60)),and 90°(P_(90)).Computational fluid dynamics(CFD)method is adopted to solve the flow pass the Terebridae-inspired structures,and the vibration equation is solved using the Newmark-βmethod.The results show that for P_(30),P_(60) and P_(90),the VIV responses are effectively suppressed in the lock-in region,and P_(60) showed the best VIV suppression performance.The transverse amplitude and the downstream amplitude can be reduced by 82.67%and 91.43%respectively for P_(60) compared with that for P0,and the peak of the mean-drag coefficient is suppressed by 53.33%.The Q-criterion vortices of P_(30),P_(60),and P_(90) are destroyed,with irregular vortices shedding.It is also found that the boundary layer separation is located on the Terebridae-inspired ribs.The twisted ribs cause the separation point to constantly change along the spanwise direction,resulting in the development of the boundary layer separation being completely destroyed.The strength of the wake flow is significantly weakened for the Terebridae-inspired cylinder.展开更多
Downhole vortex drainage gas recovery is a new gas production technology.So far,however,the forces and motions of liquid phase in the swirling flow field of wellbores during its field application have not been figured...Downhole vortex drainage gas recovery is a new gas production technology.So far,however,the forces and motions of liquid phase in the swirling flow field of wellbores during its field application have not been figured out.In this paper,the forces of liquid droplets in the swirling flow field of wellbores were analyzed on the basis of two-phase fluid dynamics theories.Then,the motion equations of fluid droplets along axial and radical directions were established.Magnitude comparison was performed on several typical acting forces,including Basset force,virtual mass force,Magnus force,Saffman force and Stokes force.Besides,the formula for calculating the optimal helical angle of vortex tools was established according to the principle that the vertical resultant force on fluid droplets should be the maximum.And afterwards,each acting force was comprehensively analyzed in terms of its origin,characteristics and direction based on the established force analysis model.Magnitude comparison indicates that the forces with less effect can be neglected,including virtual mass force,Basset force and convection volume force.Moreover,the vertically upward centrifugal force component occurs on the fluid droplets in swirling flow field instead of those in the conventional flow field of wellbores,which is favorable for the fluid droplets to move upward.The reliability of optimal helical angle calculation formula was verified by means of case analysis.It is demonstrated that with the decrease of well depth,the fluid-carrying capability of gas and the optimal helical angle increase.The research results in this paper have a guiding significance to the optimization design of downhole vortex tools and the field application of downhole vortex drainage gas recovery technology.展开更多
基金supported by the Joint Postdoc Scheme with Non-local Institutions of the Hong Kong Polytechnic University(Grant No.1-YY4P).
文摘Biomimetic design has recently received widespread attention.Inspired by the Terebridae structure,this paper provides a structural form for suppressing vortex-induced vibration(VIV)response.Four different structural forms are shown,including the traditional smooth cylinder(P0),and the Terebridae-inspired cylinder with the helical angle of 30°(P_(30)),60°(P_(60)),and 90°(P_(90)).Computational fluid dynamics(CFD)method is adopted to solve the flow pass the Terebridae-inspired structures,and the vibration equation is solved using the Newmark-βmethod.The results show that for P_(30),P_(60) and P_(90),the VIV responses are effectively suppressed in the lock-in region,and P_(60) showed the best VIV suppression performance.The transverse amplitude and the downstream amplitude can be reduced by 82.67%and 91.43%respectively for P_(60) compared with that for P0,and the peak of the mean-drag coefficient is suppressed by 53.33%.The Q-criterion vortices of P_(30),P_(60),and P_(90) are destroyed,with irregular vortices shedding.It is also found that the boundary layer separation is located on the Terebridae-inspired ribs.The twisted ribs cause the separation point to constantly change along the spanwise direction,resulting in the development of the boundary layer separation being completely destroyed.The strength of the wake flow is significantly weakened for the Terebridae-inspired cylinder.
基金Project supported by the National Major S&T Project(No.:2011ZX05009-005)Beijing Natural Science Foundation for Youth Project(No.:3154039)Sinopec Technical Development Project(No.:34400004-14-ZC0607-0001).
文摘Downhole vortex drainage gas recovery is a new gas production technology.So far,however,the forces and motions of liquid phase in the swirling flow field of wellbores during its field application have not been figured out.In this paper,the forces of liquid droplets in the swirling flow field of wellbores were analyzed on the basis of two-phase fluid dynamics theories.Then,the motion equations of fluid droplets along axial and radical directions were established.Magnitude comparison was performed on several typical acting forces,including Basset force,virtual mass force,Magnus force,Saffman force and Stokes force.Besides,the formula for calculating the optimal helical angle of vortex tools was established according to the principle that the vertical resultant force on fluid droplets should be the maximum.And afterwards,each acting force was comprehensively analyzed in terms of its origin,characteristics and direction based on the established force analysis model.Magnitude comparison indicates that the forces with less effect can be neglected,including virtual mass force,Basset force and convection volume force.Moreover,the vertically upward centrifugal force component occurs on the fluid droplets in swirling flow field instead of those in the conventional flow field of wellbores,which is favorable for the fluid droplets to move upward.The reliability of optimal helical angle calculation formula was verified by means of case analysis.It is demonstrated that with the decrease of well depth,the fluid-carrying capability of gas and the optimal helical angle increase.The research results in this paper have a guiding significance to the optimization design of downhole vortex tools and the field application of downhole vortex drainage gas recovery technology.
