Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition. It is indicated tha...Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition. It is indicated that when A U2oo- A U850 〉0 in the eastern tropical Pacific and A U2oo- A U850 〈0 in western tropical Pacific, the Walker cell is stronger in the Pacific tropical region and the annual frequency of NW Pacific tropical cyclone are above normal. In the years with zonal wind anomalies, the circulation of high and low troposphere and the vertical motions in the troposphere have significant characteristics. In the time scale of short-range climate prediction, zonal wind anomalies in high and low troposphere are useful as a preliminary signal of the annual frequency prediction of NW Pacific tropical cyclones.展开更多
The characteristics of tropical cyclone(TC) tilts under vertically varying background flows were preliminarily examined in this study based on numerical simulations with the Tropical Cyclone Model version 4(TCM4).The ...The characteristics of tropical cyclone(TC) tilts under vertically varying background flows were preliminarily examined in this study based on numerical simulations with the Tropical Cyclone Model version 4(TCM4).The tilt magnitudes presented a linearly decreasing tendency in the simulation with the environmental wind speed vertically varying throughout the troposphere and in the simulation with the vertical wind shear concentrated in the lower troposphere,while the vortex tilt showed a linearly increasing tendency in magnitude in the simulation where the vertical shear was concentrated in the upper troposphere.The change in tilt magnitude was found to be related to the evolution of the penetration depth near the eyewall.When the shear was concentrated in the lower troposphere,the vortex tended to tilt downshear right during the early integration and underwent more precession processes.When the shear was concentrated in the upper troposphere,the vortex rapidly tilted downshear left during the early simulation and vortex precession was less frequently observed.The storms simulated in all experiments were finally in downshear-left tilt equilibrium.展开更多
The thermal performance of a rectangular loop with a horizontal heating segment and a partly cooling vertical leg is studied. By one-dimensional approach, traditional friction factor and empirical correlation, a modif...The thermal performance of a rectangular loop with a horizontal heating segment and a partly cooling vertical leg is studied. By one-dimensional approach, traditional friction factor and empirical correlation, a modified Grashof number Gr* which turns out to be very important in the description of circulation flow is introduced. A new correlation for Nusselt number of the horizontal heater is obtained and the comparison with experimental raines shows good agreement.展开更多
Numerical computations are performed for the natural convection in circular enclosures with inner polygonal cylinders.The polygon surface and the outer envelope are at constant but different temperatures,A body-fitted...Numerical computations are performed for the natural convection in circular enclosures with inner polygonal cylinders.The polygon surface and the outer envelope are at constant but different temperatures,A body-fitted coordinate system is used,The coordinate system is generated via simple algebraic equations.The transformed governing equations are discretized on a control volume basis with power-law finite difference scheme.The SIMPLE-like algorithm is used to deal with the linkage between pressure and velocities.The numerical results are compared with the experimental data available in the literature,and the agreement between the numerical and experimental results are very good.展开更多
Natural convection heat transfer in eccentric annuli made of two isothermal horizontal circular cylinders is numerically investigated. Bipolar coordinates are used for the eccentric annuli. The governingequations are ...Natural convection heat transfer in eccentric annuli made of two isothermal horizontal circular cylinders is numerically investigated. Bipolar coordinates are used for the eccentric annuli. The governingequations are transformed into finite difference equations (FDE) by the central difference approach.Heat transfer and flow convection pattern results are simulated for 5.0≤RaL≤1.0×105, withPr = 0.3 - 100, Do/Di = 1.25 - 5.0, andε= 0.01-0.95. The axis of the inner cylinder lies onan inclined plane with θp= 0°- 180°.A Mach-Zehnder interferometer is used for the experimentalstudy. The range is for RaL = 5.3×102-2.41×104, with Do/Di = 2.0, 2.5 and 3.125,ε= 0.0-0.85,and θp= 0°-180°.Air is used as the medium. Comparison of the numerical results with the experimental data shows good agreement.展开更多
The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by ...The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by linear stability analysis and corresponding pattern selection mechanisms are discussed.The nonlinear evolution of different flow patterns and the convective heat transfer are simulated.The transition to oscillatory flow is also given by stability analysis where the base flow is a steady three dimensional flow.The stability predictions are in good agreement with the numerical simulations,including both the growth rate and the dimensionless frequency.展开更多
基金Research on predictive signals and methods for short-short climate of annual frequency oftyphoons, a project from the research fund on typhoons of 2003 – 2004 at Shanghai Typhoon Institute
文摘Relationships between large-scale zonal wind anomalies and annual frequency of NW Pacific tropical cyclones and possible mechanisms are investigated with the methods of correlation and composition. It is indicated that when A U2oo- A U850 〉0 in the eastern tropical Pacific and A U2oo- A U850 〈0 in western tropical Pacific, the Walker cell is stronger in the Pacific tropical region and the annual frequency of NW Pacific tropical cyclone are above normal. In the years with zonal wind anomalies, the circulation of high and low troposphere and the vertical motions in the troposphere have significant characteristics. In the time scale of short-range climate prediction, zonal wind anomalies in high and low troposphere are useful as a preliminary signal of the annual frequency prediction of NW Pacific tropical cyclones.
基金jointly supported by the National(Key)Basic Research and Development(973)Program of China(No.2015CB452803)the National Natural Science Foundation of China(Nos.41475058 and 41375068)+1 种基金the Open Project of the State Key Laboratory of Severe Weather(No.2016LASW-B08)the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)
文摘The characteristics of tropical cyclone(TC) tilts under vertically varying background flows were preliminarily examined in this study based on numerical simulations with the Tropical Cyclone Model version 4(TCM4).The tilt magnitudes presented a linearly decreasing tendency in the simulation with the environmental wind speed vertically varying throughout the troposphere and in the simulation with the vertical wind shear concentrated in the lower troposphere,while the vortex tilt showed a linearly increasing tendency in magnitude in the simulation where the vertical shear was concentrated in the upper troposphere.The change in tilt magnitude was found to be related to the evolution of the penetration depth near the eyewall.When the shear was concentrated in the lower troposphere,the vortex tended to tilt downshear right during the early integration and underwent more precession processes.When the shear was concentrated in the upper troposphere,the vortex rapidly tilted downshear left during the early simulation and vortex precession was less frequently observed.The storms simulated in all experiments were finally in downshear-left tilt equilibrium.
文摘The thermal performance of a rectangular loop with a horizontal heating segment and a partly cooling vertical leg is studied. By one-dimensional approach, traditional friction factor and empirical correlation, a modified Grashof number Gr* which turns out to be very important in the description of circulation flow is introduced. A new correlation for Nusselt number of the horizontal heater is obtained and the comparison with experimental raines shows good agreement.
文摘Numerical computations are performed for the natural convection in circular enclosures with inner polygonal cylinders.The polygon surface and the outer envelope are at constant but different temperatures,A body-fitted coordinate system is used,The coordinate system is generated via simple algebraic equations.The transformed governing equations are discretized on a control volume basis with power-law finite difference scheme.The SIMPLE-like algorithm is used to deal with the linkage between pressure and velocities.The numerical results are compared with the experimental data available in the literature,and the agreement between the numerical and experimental results are very good.
文摘Natural convection heat transfer in eccentric annuli made of two isothermal horizontal circular cylinders is numerically investigated. Bipolar coordinates are used for the eccentric annuli. The governingequations are transformed into finite difference equations (FDE) by the central difference approach.Heat transfer and flow convection pattern results are simulated for 5.0≤RaL≤1.0×105, withPr = 0.3 - 100, Do/Di = 1.25 - 5.0, andε= 0.01-0.95. The axis of the inner cylinder lies onan inclined plane with θp= 0°- 180°.A Mach-Zehnder interferometer is used for the experimentalstudy. The range is for RaL = 5.3×102-2.41×104, with Do/Di = 2.0, 2.5 and 3.125,ε= 0.0-0.85,and θp= 0°-180°.Air is used as the medium. Comparison of the numerical results with the experimental data shows good agreement.
基金supported by the National Natural Science Foundation of China (Grant No. 11072238)the 111 Project of China (Grant No. B07-033)
文摘The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by linear stability analysis and corresponding pattern selection mechanisms are discussed.The nonlinear evolution of different flow patterns and the convective heat transfer are simulated.The transition to oscillatory flow is also given by stability analysis where the base flow is a steady three dimensional flow.The stability predictions are in good agreement with the numerical simulations,including both the growth rate and the dimensionless frequency.