Experimental studies which focus on flow visualization and the velocity field of a supersonic laminar/turbulent flow over a compression ramp were carried out in a Mach 3.0 wind tunnel. Fine flow structures and velocit...Experimental studies which focus on flow visualization and the velocity field of a supersonic laminar/turbulent flow over a compression ramp were carried out in a Mach 3.0 wind tunnel. Fine flow structures and velocity field structures were obtained via NPLS （nanoparticle-tracer planar laser scattering） and PIV （particle image velocimetry） techniques, time- averaged flow structures were researched, and spatiotemporal evolutions of transient flow structures were analyzed. The flow visualization results indicated that when the ramp angles were 25~, a typical separation occurred in the laminar flow, some typical flow structures such as shock induced by the boundary layer, separation shock, reversed flow and reattachment shock were visible clearly. While a certain extent separation occurred in turbulent flow, the separation region was much smaller. When the ramp angles were 28~, laminar flow separated further, and the separation region expanded evidently, flow structures in the separation region were complex. While a typical separation occurred in turbulent flow, reversed flow structures were significant, flow structures in the separation region were relatively simple. The experimental results of velocity field were corresponding to flow visualization, and the velocity field structures of both compression ramp flows agreed with the flow structures well. There were three layered structures in the U component velocity, and the V component velocity appeared like an oblique ＂v＂. Some differences between these two compression ramp flows can be observed in the velocity profiles of the shear layer and the shearing intensity.展开更多
In this paper, the eddy coefficient and the treatment for dividing layers of Estoque's numerical model in modern PBL dynamics have been applied to derive order-zero and order-one analytic solutions over large-scal...In this paper, the eddy coefficient and the treatment for dividing layers of Estoque's numerical model in modern PBL dynamics have been applied to derive order-zero and order-one analytic solutions over large-scale topography, the solutions are used to obtain the divergence and vertical velocity, improving the previous results.展开更多
Turbulent agglomeration is a promising pretreatment technology for improving the removal of fine particles in industrial flue gas,which can improve the particle removal effect of dust removal equipment safely and econ...Turbulent agglomeration is a promising pretreatment technology for improving the removal of fine particles in industrial flue gas,which can improve the particle removal effect of dust removal equipment safely and economically.However,due to the complexity of turbulence mechanisms,the relationship between turbulent flow fields and the agglomeration of fine particles is not known with precision,resulting a weak promotion effect for particle removal with this pretreatment technology.In this work,three kinds of turbulent agglomerators were constructed to investigate the agglomeration and removal characteristics of fine particles under different turbulent flow fields.The results demonstrated that the turbulent agglomerator with small-scale and three-dimensional vortexes in the flow field had the best effect in improving the agglomeration and removal of fine particles.Two kinds of agglomeration modes in turbulent agglomeration were proposed,one being agglomeration between fine particles in the vortex area,and the other the capture of fine particles by coarse particles.Furthermore,the motion trajectory,relative velocity and residence time of fine particles of different sizes in different flow fields were calculated by numerical simulation to investigate the interaction mechanism of particle agglomeration and turbulent flow fields.The results showed that a flow field with smallscale and three-dimensional vortexes can reduce the Stokes number(StK) and the relative velocity of particles of different sizes,and extend their residence time in a turbulent flow field,so as to obtain a better agglomeration effect for fine particles.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11172326 and 11302256)
文摘Experimental studies which focus on flow visualization and the velocity field of a supersonic laminar/turbulent flow over a compression ramp were carried out in a Mach 3.0 wind tunnel. Fine flow structures and velocity field structures were obtained via NPLS （nanoparticle-tracer planar laser scattering） and PIV （particle image velocimetry） techniques, time- averaged flow structures were researched, and spatiotemporal evolutions of transient flow structures were analyzed. The flow visualization results indicated that when the ramp angles were 25~, a typical separation occurred in the laminar flow, some typical flow structures such as shock induced by the boundary layer, separation shock, reversed flow and reattachment shock were visible clearly. While a certain extent separation occurred in turbulent flow, the separation region was much smaller. When the ramp angles were 28~, laminar flow separated further, and the separation region expanded evidently, flow structures in the separation region were complex. While a typical separation occurred in turbulent flow, reversed flow structures were significant, flow structures in the separation region were relatively simple. The experimental results of velocity field were corresponding to flow visualization, and the velocity field structures of both compression ramp flows agreed with the flow structures well. There were three layered structures in the U component velocity, and the V component velocity appeared like an oblique ＂v＂. Some differences between these two compression ramp flows can be observed in the velocity profiles of the shear layer and the shearing intensity.
基金This work was supported by National Natural Science Foundation of China
文摘In this paper, the eddy coefficient and the treatment for dividing layers of Estoque's numerical model in modern PBL dynamics have been applied to derive order-zero and order-one analytic solutions over large-scale topography, the solutions are used to obtain the divergence and vertical velocity, improving the previous results.
基金supported by the National Key Research and Development Program of China (No.2016YFB0600602)the National Natural Science Foundation of China (No.51806107)the Scientific Research Foundation of Graduate School of Southeast University (No.3203009749).
文摘Turbulent agglomeration is a promising pretreatment technology for improving the removal of fine particles in industrial flue gas,which can improve the particle removal effect of dust removal equipment safely and economically.However,due to the complexity of turbulence mechanisms,the relationship between turbulent flow fields and the agglomeration of fine particles is not known with precision,resulting a weak promotion effect for particle removal with this pretreatment technology.In this work,three kinds of turbulent agglomerators were constructed to investigate the agglomeration and removal characteristics of fine particles under different turbulent flow fields.The results demonstrated that the turbulent agglomerator with small-scale and three-dimensional vortexes in the flow field had the best effect in improving the agglomeration and removal of fine particles.Two kinds of agglomeration modes in turbulent agglomeration were proposed,one being agglomeration between fine particles in the vortex area,and the other the capture of fine particles by coarse particles.Furthermore,the motion trajectory,relative velocity and residence time of fine particles of different sizes in different flow fields were calculated by numerical simulation to investigate the interaction mechanism of particle agglomeration and turbulent flow fields.The results showed that a flow field with smallscale and three-dimensional vortexes can reduce the Stokes number(StK) and the relative velocity of particles of different sizes,and extend their residence time in a turbulent flow field,so as to obtain a better agglomeration effect for fine particles.
