The bubble drag force correlation plays an important role in the numerical simulation accuracy of gas/liquid flows.In order to systematically investigate the interphase drag force of non-buoyancy driven bubbly flows,a...The bubble drag force correlation plays an important role in the numerical simulation accuracy of gas/liquid flows.In order to systematically investigate the interphase drag force of non-buoyancy driven bubbly flows,a dynamic-positioning body force(DPBF)method is developed in this study.It is proved that this method has an enough computation precision.Using this method,a series of direct numerical simulation(DNS)cases of a single bubble with low-intermediate Re(1≤Re≤200)and a bubble swarm with low Re(5.6≤Re≤45)are carried out and the bubble drag coefficients are calculated.Based on all the DNS data,the drag correlations with dimensionless parameters(Re,We for a single bubble and Re,We,gas fraction for bubble swarm)are systematically investigated and reported in this paper,which can provide a reference to the development of drag force closure model for non-buoyancy driven bubbly flows.展开更多
We perform a series of experiments to study the velocity fluctuations generated by the flow past fixed spheres.Planar particle image velocimetry(PIV)is carried out to characterize the properties of the liquid fluctuat...We perform a series of experiments to study the velocity fluctuations generated by the flow past fixed spheres.Planar particle image velocimetry(PIV)is carried out to characterize the properties of the liquid fluctuation.The fluctuation induced by the spheres can be decomposed into the temporal fluctuation and the spatial fluctuation,which represent the contribution of flow instability and spatial inhomogeneity,respectively.In particularly,we focus on the contributions of temporal fluctuations and spatial fluctuations between low and high Reynolds number.At low Reynolds number(20<Re≤200),the total fluctuation mostly comes from the spatial fluctuation and increases as the area of velocity deficit in the wake of the sphere increases.The temporal fluctuation cannot be neglected at larger Reynolds number(200<Re≤700),and the total velocity fluctuation is induced by both flow instability and spatial inhomogeneity.Furthermore,the energy distribution in the flow direction and the span direction also changes drastically as the Reynolds number increases.The wavenumber spectra of fluctuations show a−3 slope at large scale,−5/3 slope at small scale.The starting scale of the−3 slope decreases with the increase of the Reynolds number.Specifically,it is consistent with the integral length scaleΛfor Re>200,but not for Re<200.The ending scale is aroundλ=0.5d and decreases slightly as Re increases.展开更多
基金Project supported by the State Key Program of National Natural Science of China(Grant No.91852204)the National Natural Science Foundation of China(Grant No.11772298).
文摘The bubble drag force correlation plays an important role in the numerical simulation accuracy of gas/liquid flows.In order to systematically investigate the interphase drag force of non-buoyancy driven bubbly flows,a dynamic-positioning body force(DPBF)method is developed in this study.It is proved that this method has an enough computation precision.Using this method,a series of direct numerical simulation(DNS)cases of a single bubble with low-intermediate Re(1≤Re≤200)and a bubble swarm with low Re(5.6≤Re≤45)are carried out and the bubble drag coefficients are calculated.Based on all the DNS data,the drag correlations with dimensionless parameters(Re,We for a single bubble and Re,We,gas fraction for bubble swarm)are systematically investigated and reported in this paper,which can provide a reference to the development of drag force closure model for non-buoyancy driven bubbly flows.
基金supported by the State Key Program of National Natural Science of China(Grant No.91852204)the National Natural Science Foundation of China(Grant No.11772298).
文摘We perform a series of experiments to study the velocity fluctuations generated by the flow past fixed spheres.Planar particle image velocimetry(PIV)is carried out to characterize the properties of the liquid fluctuation.The fluctuation induced by the spheres can be decomposed into the temporal fluctuation and the spatial fluctuation,which represent the contribution of flow instability and spatial inhomogeneity,respectively.In particularly,we focus on the contributions of temporal fluctuations and spatial fluctuations between low and high Reynolds number.At low Reynolds number(20<Re≤200),the total fluctuation mostly comes from the spatial fluctuation and increases as the area of velocity deficit in the wake of the sphere increases.The temporal fluctuation cannot be neglected at larger Reynolds number(200<Re≤700),and the total velocity fluctuation is induced by both flow instability and spatial inhomogeneity.Furthermore,the energy distribution in the flow direction and the span direction also changes drastically as the Reynolds number increases.The wavenumber spectra of fluctuations show a−3 slope at large scale,−5/3 slope at small scale.The starting scale of the−3 slope decreases with the increase of the Reynolds number.Specifically,it is consistent with the integral length scaleΛfor Re>200,but not for Re<200.The ending scale is aroundλ=0.5d and decreases slightly as Re increases.
