Three kinds of rotating-stream tray（RST）separators were designed and designated as S1,S2 and S3.The separator S1 had double flow paths,while S2 and S3 had single flow path.The trays of S1 and S2 were the same of the...Three kinds of rotating-stream tray（RST）separators were designed and designated as S1,S2 and S3.The separator S1 had double flow paths,while S2 and S3 had single flow path.The trays of S1 and S2 were the same of the double-path type,which was different from the conventional outward tray of S3.Measurements of three-dimensional flow in the three RST separators were conducted at the same total gas flow rate and streamlines were given through calculation according to the measured data.Compared with the RST separators S2 and S3,the separator S1 not only reduced the separation distance,but also effectively increased the tangential velocity,especially in the neighborhood of the separator center.The structure of tray vanes had a great effect on the velocity profiles,especially on the axial velocity profiles.The maximal axial velocities of S1 and S2 near the separator wall were much lower than that of S3.The maximal axial velocity of S1 decreased by above 37% against that of S3,which was favorable for reducing the secondary carry-over in the two-phase separation process.Streamlines showed that the separator S3 had vortex rings over the whole axial section,while the separator S1 had vortex ring only near the tray vanes.The separator outlet baffle could increase the tangential velocity,moderate the axial velocity,and reduce the centripetal velocity.展开更多
This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles,including Reynolds stress,turbulence intensity and bursting analysis of open channel f...This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles,including Reynolds stress,turbulence intensity and bursting analysis of open channel flow.Different vegetation densities have been built between the adjacent vegetations,and the flow measurements are taken using acoustic Doppler velocimeter(ADV)at the locations within and downstream of the vegetation panel.Three different tests are conducted,where the first test has compact vegetations,while the second and the third tests have open spaces created by one and two empty vegetation slots within the vegetated field.Observation reveals that over 10%of eddies size is generated within the vegetated zone of compact vegetations as compared with the fewer vegetations.Significant turbulence structures variation is also observed at the points in the non-vegetated row.The findings from burst-cycle analysis show that the sweep and outward interaction events are dominant,where they further increase away from the bed.The effect of vegetation on the turbulent burst cycle is mostly obvious up to approximately two-third of vegetation height where this phenomenon is also observed for most other turbulent structure.展开更多
The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic ...The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic and sedimentary environments. In this study the impact was investigated, based on synchronized multi-station data from continuous observations made within and around the culture area. In total, three current velocity profiles were identified inside and on the landward side of the culture area. Based on the current velocity profiles we calculated the boundary layer parameters, the fluxes of erosion/deposition, and the rate of sediment transport in different times at each observation site. Comparison between culture and non-culture periods showed that the presence of suspended kelp caused the reduction in the average flow velocity by approximately 49.5%, the bottom friction velocity by 24.8%, the seabed roughness length by 62.7%, and the shear stress and the flux of resuspended sediment by approximately 50%. From analyses in combination with the corresponding vertical variation of the suspended sediment distribution, it is revealed that the lifted sediments by resuspension is mixed with the upper suspended material, which will modify the regional distribution of suspended sediment. These changes in flow structure and sediment movement will accelerate seabed siltation, which corresponds to the changes in seabed erosion/deposition. However, under the influences of the seasonal changes in kelp growth the magnitude of change with the seabed siltation was not obvious inside the culture area, but a fundamental change was apparent around the culture area.展开更多
In natural rivers,patches of vegetation generally expand over their steady wake region in the streamwise direction,forming elongated patches with length(L)greater than their width(b).This paper studies how the wake fl...In natural rivers,patches of vegetation generally expand over their steady wake region in the streamwise direction,forming elongated patches with length(L)greater than their width(b).This paper studies how the wake flows and the vortices develop as the emergent patches expand their length in the streamwise direction.The patches are modeled with the same width but different lengths in laboratory experiments.Behind the patches,the steady wake region(L_(w))is not related to the width-related flow blockage(C_(d)ab),where C_(d) is the drag coefficient,a is the vegetation density.Instead,L_(w) is related to the length-related flow blockage(C_(d)aL).On this basis,a model is proposed for predicting L_(w),which is in good agreement with the measurements.As a patch becomes denser and/or longer(as C_(d)aL increases),the steady wake region becomes shorter(L_(w) decreases),and vortices are observed closer to the patch trailing edge,producing a turbulence of a greater magnitude beyond L_(w).When the flow blockage increases to the limit(C_(d)aL>8),the Karman vortices are observed directly behind the porous patches.These results can be used to explain the longitudinal elongation of the vegetation patches in the field.展开更多
In the present study,among six gravel-bed river reaches,two natural gravel-bed river reaches with approximately similar bedforms and flow conditions have been found,one river reach with vegetation on bedforms and the ...In the present study,among six gravel-bed river reaches,two natural gravel-bed river reaches with approximately similar bedforms and flow conditions have been found,one river reach with vegetation on bedforms and the other without vegetation on bedforms.Based on field measurements,the impacts of vegetation over bedforms on flow characteristics have been investigated.Flow velocity,Reynolds stress and turbulence intensity distributions over bedforms with vegetation have been compared with those over gravel bedforms without vegetation.By using the quadrant analysis,the dominant events of turbulent flow structures have been assessed for flows over gravel bedforms with vegetation and without vegetation.Results show that the effect of vegetation enhances the anisotropy in turbulence and generates strong secondary currents,which lead to the occurrence of dip phenomenon at the stoss section and the crest of vegetated bedforms.The change of bed roughness from gravel bed to vegetated bed causes a development of a new boundary layer.This resulted in the different shape of velocity distributions over bedforms with vegetation from those over bedforms without vegetation,which can affect the lives of aquatic animals.Reynolds shear stress at downstream section of gravel bedform without vegetation is much higher than that of vegetated bedform,which shows that the erosion takes place from downstream of vegetated bedforms,while in the bare beds;the deposition is at downstream of bedforms.It is found that the presence of vegetation causes a chaotic distribution pattern of Reynolds shear stress,while it has more orderly pattern at the downstream section of gravel bedform without vegetation.Besides,the distribution of turbulence intensity in the lee side of vegetated bedform has a concave shape and in the stoss section,turbulence is generated in ejections and sweeps near the vegetation cover.These findings are significant to the practice of river ecological restoration.展开更多
文摘Three kinds of rotating-stream tray（RST）separators were designed and designated as S1,S2 and S3.The separator S1 had double flow paths,while S2 and S3 had single flow path.The trays of S1 and S2 were the same of the double-path type,which was different from the conventional outward tray of S3.Measurements of three-dimensional flow in the three RST separators were conducted at the same total gas flow rate and streamlines were given through calculation according to the measured data.Compared with the RST separators S2 and S3,the separator S1 not only reduced the separation distance,but also effectively increased the tangential velocity,especially in the neighborhood of the separator center.The structure of tray vanes had a great effect on the velocity profiles,especially on the axial velocity profiles.The maximal axial velocities of S1 and S2 near the separator wall were much lower than that of S3.The maximal axial velocity of S1 decreased by above 37% against that of S3,which was favorable for reducing the secondary carry-over in the two-phase separation process.Streamlines showed that the separator S3 had vortex rings over the whole axial section,while the separator S1 had vortex ring only near the tray vanes.The separator outlet baffle could increase the tangential velocity,moderate the axial velocity,and reduce the centripetal velocity.
文摘This study presents results from a vegetation-induced flow experimental study which investigates 3-D turbulence structure profiles,including Reynolds stress,turbulence intensity and bursting analysis of open channel flow.Different vegetation densities have been built between the adjacent vegetations,and the flow measurements are taken using acoustic Doppler velocimeter(ADV)at the locations within and downstream of the vegetation panel.Three different tests are conducted,where the first test has compact vegetations,while the second and the third tests have open spaces created by one and two empty vegetation slots within the vegetated field.Observation reveals that over 10%of eddies size is generated within the vegetated zone of compact vegetations as compared with the fewer vegetations.Significant turbulence structures variation is also observed at the points in the non-vegetated row.The findings from burst-cycle analysis show that the sweep and outward interaction events are dominant,where they further increase away from the bed.The effect of vegetation on the turbulent burst cycle is mostly obvious up to approximately two-third of vegetation height where this phenomenon is also observed for most other turbulent structure.
基金funded by the National Natural Science Foundation of China, Nos.41076031 and 41106041
文摘The culture of suspended kelp, such as Laminaria japonica Aresch, has arisen in nearshore areas for approximately 30 years since the 1980 s. This long-term activity has significant impact on the regional hydrodynamic and sedimentary environments. In this study the impact was investigated, based on synchronized multi-station data from continuous observations made within and around the culture area. In total, three current velocity profiles were identified inside and on the landward side of the culture area. Based on the current velocity profiles we calculated the boundary layer parameters, the fluxes of erosion/deposition, and the rate of sediment transport in different times at each observation site. Comparison between culture and non-culture periods showed that the presence of suspended kelp caused the reduction in the average flow velocity by approximately 49.5%, the bottom friction velocity by 24.8%, the seabed roughness length by 62.7%, and the shear stress and the flux of resuspended sediment by approximately 50%. From analyses in combination with the corresponding vertical variation of the suspended sediment distribution, it is revealed that the lifted sediments by resuspension is mixed with the upper suspended material, which will modify the regional distribution of suspended sediment. These changes in flow structure and sediment movement will accelerate seabed siltation, which corresponds to the changes in seabed erosion/deposition. However, under the influences of the seasonal changes in kelp growth the magnitude of change with the seabed siltation was not obvious inside the culture area, but a fundamental change was apparent around the culture area.
基金Projects supported by the National Natural Science Foundation of China(52022063,52179074 and U2040219).
文摘In natural rivers,patches of vegetation generally expand over their steady wake region in the streamwise direction,forming elongated patches with length(L)greater than their width(b).This paper studies how the wake flows and the vortices develop as the emergent patches expand their length in the streamwise direction.The patches are modeled with the same width but different lengths in laboratory experiments.Behind the patches,the steady wake region(L_(w))is not related to the width-related flow blockage(C_(d)ab),where C_(d) is the drag coefficient,a is the vegetation density.Instead,L_(w) is related to the length-related flow blockage(C_(d)aL).On this basis,a model is proposed for predicting L_(w),which is in good agreement with the measurements.As a patch becomes denser and/or longer(as C_(d)aL increases),the steady wake region becomes shorter(L_(w) decreases),and vortices are observed closer to the patch trailing edge,producing a turbulence of a greater magnitude beyond L_(w).When the flow blockage increases to the limit(C_(d)aL>8),the Karman vortices are observed directly behind the porous patches.These results can be used to explain the longitudinal elongation of the vegetation patches in the field.
文摘In the present study,among six gravel-bed river reaches,two natural gravel-bed river reaches with approximately similar bedforms and flow conditions have been found,one river reach with vegetation on bedforms and the other without vegetation on bedforms.Based on field measurements,the impacts of vegetation over bedforms on flow characteristics have been investigated.Flow velocity,Reynolds stress and turbulence intensity distributions over bedforms with vegetation have been compared with those over gravel bedforms without vegetation.By using the quadrant analysis,the dominant events of turbulent flow structures have been assessed for flows over gravel bedforms with vegetation and without vegetation.Results show that the effect of vegetation enhances the anisotropy in turbulence and generates strong secondary currents,which lead to the occurrence of dip phenomenon at the stoss section and the crest of vegetated bedforms.The change of bed roughness from gravel bed to vegetated bed causes a development of a new boundary layer.This resulted in the different shape of velocity distributions over bedforms with vegetation from those over bedforms without vegetation,which can affect the lives of aquatic animals.Reynolds shear stress at downstream section of gravel bedform without vegetation is much higher than that of vegetated bedform,which shows that the erosion takes place from downstream of vegetated bedforms,while in the bare beds;the deposition is at downstream of bedforms.It is found that the presence of vegetation causes a chaotic distribution pattern of Reynolds shear stress,while it has more orderly pattern at the downstream section of gravel bedform without vegetation.Besides,the distribution of turbulence intensity in the lee side of vegetated bedform has a concave shape and in the stoss section,turbulence is generated in ejections and sweeps near the vegetation cover.These findings are significant to the practice of river ecological restoration.
