Based on the study of hydraulic characteristics of the sudden expansion water flow of an annular flume, this paper determines the vertical velocity distribution and the turbulence intensity distribution in the mainstr...Based on the study of hydraulic characteristics of the sudden expansion water flow of an annular flume, this paper determines the vertical velocity distribution and the turbulence intensity distribution in the mainstream and the recirculation regions to analyze the basic features of this flow field. The adsorption of the phosphorus in the sediment is studied by adding the bacteriostatic agent. The results show that the flow speed in the mainstream region is higher than that in the recirculation region. However, the turbulence intensity in the recirculation region increases more than that in the mainstream region. The adsorption of the phosphorus in the sediment includes the physisorption and the biosorption, and the former is stronger than the latter. With the biosorption in the phosphorus removal process, the phosphorus released by the sediment is mainly completed by the poly-P bacteria in the anaerobic condition. The adsorption of the phosphorus in the sediment in the mainstream region of a sudden expansion water flow is strong and stable, whereas the adsorption in the sediment in the recirculation region is largely fluctuated.展开更多
In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by ...In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.展开更多
The size mismatch in an end-to-end vascular anastomosis between the host vessel and the graft may cause flow disturbance and predispose to thrombosis [1].Although a number of techniques have been employed to reduce th...The size mismatch in an end-to-end vascular anastomosis between the host vessel and the graft may cause flow disturbance and predispose to thrombosis [1].Although a number of techniques have been employed to reduce the risk of anastomotic thrombosis due to the size mismatch。展开更多
基金Project supported by the National Basic Research Development Program of China(973 Program,Grant No.2008CB418203)
文摘Based on the study of hydraulic characteristics of the sudden expansion water flow of an annular flume, this paper determines the vertical velocity distribution and the turbulence intensity distribution in the mainstream and the recirculation regions to analyze the basic features of this flow field. The adsorption of the phosphorus in the sediment is studied by adding the bacteriostatic agent. The results show that the flow speed in the mainstream region is higher than that in the recirculation region. However, the turbulence intensity in the recirculation region increases more than that in the mainstream region. The adsorption of the phosphorus in the sediment includes the physisorption and the biosorption, and the former is stronger than the latter. With the biosorption in the phosphorus removal process, the phosphorus released by the sediment is mainly completed by the poly-P bacteria in the anaerobic condition. The adsorption of the phosphorus in the sediment in the mainstream region of a sudden expansion water flow is strong and stable, whereas the adsorption in the sediment in the recirculation region is largely fluctuated.
基金supported by the National Natural Science Foundation of China (50606026 and 50736006)
文摘In this paper the present authors measured the gas-particle two-phase velocity correlation in sudden expansion gas-particle flows with a phase Doppler particle anemometer （PDPA） and simulated the system behavior by using both a Reynolds-averaged Navier-Stokes （RANS） model and a large-eddy simulation （LES）. The results of the measurements yield the axial and radial time-averaged velocities as well as the fluctuation velocities of gas and three particle-size groups （30μm, 50μm, and 95μm） and the gasparticle velocity correlation for 30μm and 50μm particles. From the measurements, theoretical analysis, and simulation, it is found that the two-phase velocity correlation of sudden-expansion flows, like that of jet flows, is less than the gas and particle Reynolds stresses. What distinguishes the two-phase velocity correlations of sudden-expansion flow from those of jet and channel flows is the absence of a clear relationship between the two-phase velocity correlation and particle size in sudden-expansion flows. The measurements, theoretical analysis, and numerical simulation all lead to the above-stated conclusions. Quantitatively, the results of the LES are better than those of the RANS model.
基金supported by Grants-in-Aid from the National Natural Science Foundation of China No.10632010,30670517
文摘The size mismatch in an end-to-end vascular anastomosis between the host vessel and the graft may cause flow disturbance and predispose to thrombosis [1].Although a number of techniques have been employed to reduce the risk of anastomotic thrombosis due to the size mismatch。
