The shape evolution of bubble formed in carboxymethylcellulose(CMC) aqueous solution was real-time observed using laser image technique. The flow fields of liquid around growing and rising bubble were measured by lase...The shape evolution of bubble formed in carboxymethylcellulose(CMC) aqueous solution was real-time observed using laser image technique. The flow fields of liquid around growing and rising bubble were measured by laser Doppler velocimetry(LDV), and the liquid mean velocity and its contour curves were obtained. The results show that bubble grows as spherical shape because of the dominant role of surface tension in the early period, and then is stretched gradually as a teardrop shape due to the common effect of buoyancy and shear-thinning of fluid. The axial mean velocity of liquid phase takes on Gaussian distribution with the symmetrical axis passing through orifice center. However, the radial mean velocity increases first and then decreases with the increase of the distance from measured point to the symmetrical axis above. Further, the axial component along symmetrical axis decreases initially and increases with the rise of height, as well as its corresponding contour map diverging gradually. The radial component, yet, decreases steadily with the rise of height, and the maximum value deviates towards the two sides until disappear, as it contour shape of butterfly's "front wing".展开更多
The measurement results by Laser Doppler Velocimetry (LDV) are compared with the direct numerical simulation result by Eggels et al.[1] for a cylindrical pipe flow. In the case of a pipe flow, the bias error for mean ...The measurement results by Laser Doppler Velocimetry (LDV) are compared with the direct numerical simulation result by Eggels et al.[1] for a cylindrical pipe flow. In the case of a pipe flow, the bias error for mean velocity is very small, because the local turbulent intensity is very small all over the pipe cross section. However the difference of the combination of u’ and v’ have considerable effects on Reynolds shear stress. From our investigation, it is found that the selection of coincidence time that is a necessary parameter for combination of u’ and v’ is more important in obtaining the accurate Reynolds shear stress. The suitable coincidence time is selectal for a jet flow and the effectiveness of coincident bine method or equal time interval method with coincidence data is shown.展开更多
基金Financially supported by National Natural Science Foundation of China(21076139,21106106)Tianjin Natural Science Foundation(12JCQNJC03700)Foundation of Tianjin Educational Committee of China(20100508)
文摘The shape evolution of bubble formed in carboxymethylcellulose(CMC) aqueous solution was real-time observed using laser image technique. The flow fields of liquid around growing and rising bubble were measured by laser Doppler velocimetry(LDV), and the liquid mean velocity and its contour curves were obtained. The results show that bubble grows as spherical shape because of the dominant role of surface tension in the early period, and then is stretched gradually as a teardrop shape due to the common effect of buoyancy and shear-thinning of fluid. The axial mean velocity of liquid phase takes on Gaussian distribution with the symmetrical axis passing through orifice center. However, the radial mean velocity increases first and then decreases with the increase of the distance from measured point to the symmetrical axis above. Further, the axial component along symmetrical axis decreases initially and increases with the rise of height, as well as its corresponding contour map diverging gradually. The radial component, yet, decreases steadily with the rise of height, and the maximum value deviates towards the two sides until disappear, as it contour shape of butterfly's "front wing".
文摘The measurement results by Laser Doppler Velocimetry (LDV) are compared with the direct numerical simulation result by Eggels et al.[1] for a cylindrical pipe flow. In the case of a pipe flow, the bias error for mean velocity is very small, because the local turbulent intensity is very small all over the pipe cross section. However the difference of the combination of u’ and v’ have considerable effects on Reynolds shear stress. From our investigation, it is found that the selection of coincidence time that is a necessary parameter for combination of u’ and v’ is more important in obtaining the accurate Reynolds shear stress. The suitable coincidence time is selectal for a jet flow and the effectiveness of coincident bine method or equal time interval method with coincidence data is shown.
