The turbulence in plane Couette flow subjected to system rotation is investigated. The anti-cyclonic rotation rate is well above the range in which roll-cells occurand close to the upper bound, beyond which no station...The turbulence in plane Couette flow subjected to system rotation is investigated. The anti-cyclonic rotation rate is well above the range in which roll-cells occurand close to the upper bound, beyond which no stationary turbulent states of motionexist. The mean velocity profile exhibits a linear region over 80% of the cross-section, inwhich the mean absolute vorticity is driven to zero. Viscous effects still prevail in narrow regions next to the walls, whereas the quasi-homogeneous central core exhibitsabnormal anisotropies of the Reynolds stress tensor, the vorticity tensor and the energy dissipation rate tensor. In spite of the distinctly higher turbulence level observed,a 13% drag reduction is found. This paradoxical finding is ascribed to configurationalchanges in the turbulence field brought about by the system rotation.展开更多
Particle dynamics in a turbulent channel flow is considered.The effects of particle concentration and Reynolds number on the particle velocity statistics are investigated.Four different particle response times,τ^(+)=...Particle dynamics in a turbulent channel flow is considered.The effects of particle concentration and Reynolds number on the particle velocity statistics are investigated.Four different particle response times,τ^(+)=1,5,30 and 100,are examined for three different Reynolds numbers,Re_(∗)=200,360 and 790(based on channel height and friction velocity).The particle concentration evolves with time and statistics obtained during three different sampling periods might be distinctly different.Themean and fluctuating particle velocities are substantially affected both by the particle response time and by the Reynolds number of the flow.展开更多
文摘The turbulence in plane Couette flow subjected to system rotation is investigated. The anti-cyclonic rotation rate is well above the range in which roll-cells occurand close to the upper bound, beyond which no stationary turbulent states of motionexist. The mean velocity profile exhibits a linear region over 80% of the cross-section, inwhich the mean absolute vorticity is driven to zero. Viscous effects still prevail in narrow regions next to the walls, whereas the quasi-homogeneous central core exhibitsabnormal anisotropies of the Reynolds stress tensor, the vorticity tensor and the energy dissipation rate tensor. In spite of the distinctly higher turbulence level observed,a 13% drag reduction is found. This paradoxical finding is ascribed to configurationalchanges in the turbulence field brought about by the system rotation.
基金This article is a slightly expanded version of a paper with the same title presented by the first author at”The 8th Asian Computational Fluid Dynamics Conference”in Hong Kong 10^(th)−14^(th) January 2010.The research work reported herein has been supported by A/S Norske Shell through a research fellowship(contract No.4610020178/C08156)and by the Research Council of Norway(Programme for Supercomputing)through a grant of computing time.
文摘Particle dynamics in a turbulent channel flow is considered.The effects of particle concentration and Reynolds number on the particle velocity statistics are investigated.Four different particle response times,τ^(+)=1,5,30 and 100,are examined for three different Reynolds numbers,Re_(∗)=200,360 and 790(based on channel height and friction velocity).The particle concentration evolves with time and statistics obtained during three different sampling periods might be distinctly different.Themean and fluctuating particle velocities are substantially affected both by the particle response time and by the Reynolds number of the flow.
