两个反向旋转盘片间剪切层不稳定性的实验和数值模拟研究

The shear layer instability in the flow between two counter-rotating disks enclosed by
a cylinder is investigated experimentally and numerically, for radius-to-height ratio
=R/h between 2 and 21. For sufficiently large rotation ratio, the internal shear layer
that separates two regions of opposite azimuthal velocities is prone to an azimuthal
symmetry breaking, which is investigated experimentally by means of visualization
and particle image velocimetry. The associated pattern is a combination of a sharpcornered
polygonal pattern, as observed by Lopez et al. (2002) for low aspect ratio,
surrounded by a set of spiral arms, first described by Gauthier et al. (2002) for high
aspect ratio. The spiral arms result from the interaction of the shear layer instability
with the Ekman boundary layer over the faster rotating disk. Stability curves and
critical modes are experimentally measured for the whole range of aspect ratios, and
are found to compare well with numerical simulations of the three-dimensional timedependent
NavierStokes equations over an extensive range of parameters. Measurements
of a local Reynolds number based on the shear layer thickness confirm that a
shear layer instability, with only weak curvature effect, is responsible for the observed
patterns. This scenario is supported by the observed onset modes, which scale as the
shear layer radius, and by the measured phase velocities. 德国LaVision PIV/PLIF粒子成像测速场仪