The convection structure in a rectangular channel with a horizontal flow forΓ = 12 was studied. The simulations were preformed by solving the hydrodynamic equations using theSIMPLE method. The convective behavior in ...The convection structure in a rectangular channel with a horizontal flow forΓ = 12 was studied. The simulations were preformed by solving the hydrodynamic equations using theSIMPLE method. The convective behavior in an absolutely and convectively unstable regime wasstudied. The results show that the two types of convection patterns in this system appear dependingon the convection intensity and horizontal flow. A periodically localized traveling wave state wasfound in this system.展开更多
In order to study atomization mechanism of a viscoelastic liquid sheet in an electric field, the spatial-temporal stability analysis of a viscoelastic liquid sheet injected into a dielectric station- ary ambient gas i...In order to study atomization mechanism of a viscoelastic liquid sheet in an electric field, the spatial-temporal stability analysis of a viscoelastic liquid sheet injected into a dielectric station- ary ambient gas in the presence of a vertical electric field is conducted. The dispersion relations of both sinuous and varicose disturbance modes are solved to explore the spatial-temporal instability of a charged viscoelastic sheet, by setting both the wave number and frequency complex. A para- metric study is performed to test the influence of the dimensionless parameters on the absolute instability of the sheet. The results show that the increase of liquid Weber number and time constant ratio, or decrease of gas to liquid density ratio and Reynolds number, can damp the absolute insta- bility. The effect of the liquid elasticity depends on the value of time constant ratio： when time con- stant ratio is small, the increase of liquid elasticity could amplify absolute growth rate, but the effect is weak when the elasticity number is relatively large; when time constant ratio is large, the increase of liquid elasticity cannot affect the absolute growth rate. Moreover, the variation of electrical Euler number can hardly influence the absolute instability of a charged viscoelastic sheet.展开更多
To control the Karman vortex street formed behind a thin airfoil at a certain incidence, a control cylinder was placed at the suction side apart from the airfoil in the downstream region. Both smoke visualization and ...To control the Karman vortex street formed behind a thin airfoil at a certain incidence, a control cylinder was placed at the suction side apart from the airfoil in the downstream region. Both smoke visualization and hot-wire measurements confirmed that the Karman vortex street was completely suppressed. The mechanism for suppression of the vortex street was examined with a hot-wire survey.展开更多
A three-wave interaction （3WI） code is developed to study the stimulated Raman scattering （SRS） in both absolute and convective regimes. In the simulations, the time and spatial evolutions of a plasma wave are des...A three-wave interaction （3WI） code is developed to study the stimulated Raman scattering （SRS） in both absolute and convective regimes. In the simulations, the time and spatial evolutions of a plasma wave are described by temporal growth rate and spatial factor, respectively. The spatial factors in different phases and different instability regimes are investigated. It is found that the spatial factor is caused by the finite velocity of the pump wave in the first phase and by damping in the last phase. With inclusion of the spatial factor, the temporal growth rate decreases and the threshold for SRS for a finite frequency mismatch increases. Meanwhile, the effects of wave frequency mismatch on the temporal growth rate are also discussed.展开更多
文摘The convection structure in a rectangular channel with a horizontal flow forΓ = 12 was studied. The simulations were preformed by solving the hydrodynamic equations using theSIMPLE method. The convective behavior in an absolutely and convectively unstable regime wasstudied. The results show that the two types of convection patterns in this system appear dependingon the convection intensity and horizontal flow. A periodically localized traveling wave state wasfound in this system.
基金The financial support of the National Natural Science Foundation of China (No. 11302013)
文摘In order to study atomization mechanism of a viscoelastic liquid sheet in an electric field, the spatial-temporal stability analysis of a viscoelastic liquid sheet injected into a dielectric station- ary ambient gas in the presence of a vertical electric field is conducted. The dispersion relations of both sinuous and varicose disturbance modes are solved to explore the spatial-temporal instability of a charged viscoelastic sheet, by setting both the wave number and frequency complex. A para- metric study is performed to test the influence of the dimensionless parameters on the absolute instability of the sheet. The results show that the increase of liquid Weber number and time constant ratio, or decrease of gas to liquid density ratio and Reynolds number, can damp the absolute insta- bility. The effect of the liquid elasticity depends on the value of time constant ratio： when time con- stant ratio is small, the increase of liquid elasticity could amplify absolute growth rate, but the effect is weak when the elasticity number is relatively large; when time constant ratio is large, the increase of liquid elasticity cannot affect the absolute growth rate. Moreover, the variation of electrical Euler number can hardly influence the absolute instability of a charged viscoelastic sheet.
文摘To control the Karman vortex street formed behind a thin airfoil at a certain incidence, a control cylinder was placed at the suction side apart from the airfoil in the downstream region. Both smoke visualization and hot-wire measurements confirmed that the Karman vortex street was completely suppressed. The mechanism for suppression of the vortex street was examined with a hot-wire survey.
基金supported by Sci. & Tech.Funds of CAEP(Nos.2010A0102004 and 2010B0102018)National Natural Science Foundation of China(Nos.11075025,10975023,10935003,10835003)
文摘A three-wave interaction （3WI） code is developed to study the stimulated Raman scattering （SRS） in both absolute and convective regimes. In the simulations, the time and spatial evolutions of a plasma wave are described by temporal growth rate and spatial factor, respectively. The spatial factors in different phases and different instability regimes are investigated. It is found that the spatial factor is caused by the finite velocity of the pump wave in the first phase and by damping in the last phase. With inclusion of the spatial factor, the temporal growth rate decreases and the threshold for SRS for a finite frequency mismatch increases. Meanwhile, the effects of wave frequency mismatch on the temporal growth rate are also discussed.
