The whole field measurements of swirling flow in spin-up and spin-downprocesses via PIV are presented in the paper. Investigation of the flow patterns at H/R = 1. 50 wasexperimentally carried out for the first time in...The whole field measurements of swirling flow in spin-up and spin-downprocesses via PIV are presented in the paper. Investigation of the flow patterns at H/R = 1. 50 wasexperimentally carried out for the first time in both processes. By means of symmetry analysis, itis found that the overall flow structure in the spin-up process still keep axi-symmetric to a greatextent, but deteriorated very fast in the spin-down process. The time to settle to the state of restin the spin-down process is found to be greatly shorter than the time to achieve the steady statein the spin-up process. Temporarily oscillatory vortex breakdown was discovered during the spin-upprocess, although no breakdown in the steady state at the same Reynolds number is found in preciousresearches.展开更多
Bubble-type vortex breakdown of the swirling flow inside a closed cylindricalcontainer with a rotating upper endwall was experimentally investigated via LDV. 3D measurement ofthe steady bubble at H/R =1.5 was firstly ...Bubble-type vortex breakdown of the swirling flow inside a closed cylindricalcontainer with a rotating upper endwall was experimentally investigated via LDV. 3D measurement ofthe steady bubble at H/R =1.5 was firstly carried out with very fine grid arrangement. Flow detailsinside the bubble and its Re -dependent structure were made clear. Abrupt waves of the azimuthalvelocity component were always found to be between the bottom stationary endwall and the upstreamstagnation point, which might be the reason of bubble formation. Variation of bubble structure andbubble center with the increasing Re gives the explanation for the disappearance of the breakdownregion.展开更多
文摘The whole field measurements of swirling flow in spin-up and spin-downprocesses via PIV are presented in the paper. Investigation of the flow patterns at H/R = 1. 50 wasexperimentally carried out for the first time in both processes. By means of symmetry analysis, itis found that the overall flow structure in the spin-up process still keep axi-symmetric to a greatextent, but deteriorated very fast in the spin-down process. The time to settle to the state of restin the spin-down process is found to be greatly shorter than the time to achieve the steady statein the spin-up process. Temporarily oscillatory vortex breakdown was discovered during the spin-upprocess, although no breakdown in the steady state at the same Reynolds number is found in preciousresearches.
文摘Bubble-type vortex breakdown of the swirling flow inside a closed cylindricalcontainer with a rotating upper endwall was experimentally investigated via LDV. 3D measurement ofthe steady bubble at H/R =1.5 was firstly carried out with very fine grid arrangement. Flow detailsinside the bubble and its Re -dependent structure were made clear. Abrupt waves of the azimuthalvelocity component were always found to be between the bottom stationary endwall and the upstreamstagnation point, which might be the reason of bubble formation. Variation of bubble structure andbubble center with the increasing Re gives the explanation for the disappearance of the breakdownregion.
