Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of...Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.展开更多
Based on high-resolution,Array for Real-time Geostrophic Oceanography(Argo)profiles and Sea Level Anomaly(SLA)data,this study statistically analyzes and compares turbulent diapycnal mixing profiles inside and outside ...Based on high-resolution,Array for Real-time Geostrophic Oceanography(Argo)profiles and Sea Level Anomaly(SLA)data,this study statistically analyzes and compares turbulent diapycnal mixing profiles inside and outside mesoscale eddies in the Gulf Stream region.The result indicates that average diapycnal diffusivity at 300–540 m depths in anticyclonic eddies reaches4.0×10-5 m2 s-1.This is significantly higher than the 1.6×10-5 m2 s-1 outside eddies and 0.8×10-5 m2 s-1 in cyclonic eddies.Probabilities of diapycnal diffusivity greater than 10-4 m2 s-1 within anticyclonic and cyclonic eddies and outside eddies are29%,5%and 12%,respectively.However,magnitudes of average diapycnal diffusivity at 540–900 m depths in these three cases are of the same order,10-5 m2 s-1.Twenty-four of a total 38 anticyclonic eddies had enhanced mixing in the ocean interior,and 22 were observed during or shortly after strong winds.The coincidence between enhanced mixing and strong wind stress indicates that more wind-induced,near-inertial wave energy propagates downward in anticyclonic eddies.The deeper part of 12 profiles(below 540 m)in anticyclonic eddies had vertical overturns with Thorpe scale exceeding 5 m,among which three profiles had overturns reaching 20 m.Enhanced mixing may have occurred in deep layers of some profiles,although it was not evident in average conditions.展开更多
In nuclear reactor fuel assemblies, spacer grids are installed among the rod bundles to support the fuel rods and affect the flow field between rods. Mixing vanes, as a swirling device, are set on the upper apex of th...In nuclear reactor fuel assemblies, spacer grids are installed among the rod bundles to support the fuel rods and affect the flow field between rods. Mixing vanes, as a swirling device, are set on the upper apex of the spacer grid. Vortexes produced by mixing vanes move along the axial direction in subchannels and enhance the forced convection heat transfer between the rods and cooling-fluid medium. In this paper, a numerical simulation method was used to investigate vortex motion produced by typical AFA-3G spacer grids in a 5×5-rod bundle by Star-CCM+ software. The shear-stress transport k-ω model was used to simulate turbulence phenomena. A dimensionless parameter, Se, based on the absolute vorticity flux, was reported to specify the intensity of secondary flow. Its physical meaning is the ratio of inertial force to viscous force induced by secondary flow. The results are helpful to take advantage of spacer grids in a much more effective way in pressurized water reactors.展开更多
文摘Results of experimental research of the mixing process of coaxial flows in a pipe with swirled peripheral jet are presented in this paper. Distribution of temperature and concentration of gases on the axis and wall of the channel under the influence of such factors as the regime flow, ratio of density of flows and swirl degree of the peripheral jet are studied. Research of temperature, swirl angle, circulation in cross sections along with the channel have shown that their distributions have the jet-like character and are described by known dependences for the layer of mixture.
基金supported by the National Natural Science Foundation of China(Grant Nos.41106012,41176008,91028008)a grant from Sanya Institute of Deep-Sea Science and Engineering(Grant No.SIDSSE-201207)
文摘Based on high-resolution,Array for Real-time Geostrophic Oceanography(Argo)profiles and Sea Level Anomaly(SLA)data,this study statistically analyzes and compares turbulent diapycnal mixing profiles inside and outside mesoscale eddies in the Gulf Stream region.The result indicates that average diapycnal diffusivity at 300–540 m depths in anticyclonic eddies reaches4.0×10-5 m2 s-1.This is significantly higher than the 1.6×10-5 m2 s-1 outside eddies and 0.8×10-5 m2 s-1 in cyclonic eddies.Probabilities of diapycnal diffusivity greater than 10-4 m2 s-1 within anticyclonic and cyclonic eddies and outside eddies are29%,5%and 12%,respectively.However,magnitudes of average diapycnal diffusivity at 540–900 m depths in these three cases are of the same order,10-5 m2 s-1.Twenty-four of a total 38 anticyclonic eddies had enhanced mixing in the ocean interior,and 22 were observed during or shortly after strong winds.The coincidence between enhanced mixing and strong wind stress indicates that more wind-induced,near-inertial wave energy propagates downward in anticyclonic eddies.The deeper part of 12 profiles(below 540 m)in anticyclonic eddies had vertical overturns with Thorpe scale exceeding 5 m,among which three profiles had overturns reaching 20 m.Enhanced mixing may have occurred in deep layers of some profiles,although it was not evident in average conditions.
文摘In nuclear reactor fuel assemblies, spacer grids are installed among the rod bundles to support the fuel rods and affect the flow field between rods. Mixing vanes, as a swirling device, are set on the upper apex of the spacer grid. Vortexes produced by mixing vanes move along the axial direction in subchannels and enhance the forced convection heat transfer between the rods and cooling-fluid medium. In this paper, a numerical simulation method was used to investigate vortex motion produced by typical AFA-3G spacer grids in a 5×5-rod bundle by Star-CCM+ software. The shear-stress transport k-ω model was used to simulate turbulence phenomena. A dimensionless parameter, Se, based on the absolute vorticity flux, was reported to specify the intensity of secondary flow. Its physical meaning is the ratio of inertial force to viscous force induced by secondary flow. The results are helpful to take advantage of spacer grids in a much more effective way in pressurized water reactors.
