水流中流场,漩涡检测方案
检测样品
其他
检测项目
流场,漩涡
关联设备
共3种
方案详情文
The three-dimensional behavior of flow transition in circular and 6-chevron jets at Re?000 is
investigated with experiments conducted on a free water jet by time-resolved tomographic particle
image velocimetry. The emphasis is on the unsteady organization of coherent flow structures,
which play a role in the generation of acoustic noise. Shedding and pairing of vortices are the most
pronounced phenomena observed in the near field of the circular jet. The first and second pairing
amplify the axial pulsatile motion in the jet column and lead to the growth of azimuthal waves
culminating in the breakup of the vortex ring. Streamwise vortices of axial and radial vorticity are
observed in the outer region and move inward and outward under the effect of the vortex rings. In
the jet with chevrons, the axisymmetric ring-like coherence of the circular jet is not encountered.
Instead, streamwise flow structures of azimuthal vorticity emanate from the chevron apices, and
counter-rotating streamwise vortices of axial and radial vorticity develop from the chevron notches.
The decay of streamwise vortices is accompanied by the formation of C-shaped structures. The
three-dimensional analysis allows quantifying the vortex stretching and tilting activity, which, for the
circular jet exit, is related to the azimuthal instabilities and the streamwise vortices connecting the
vortex rings. In the chevron jet, stretching and tilting peak during the formation of C-structures.
Following Powell抯 aeroacoustic analogy, the spatial distribution of the source term is mapped,
evaluating the temporal derivative of the Lamb vector. The spatio-temporal evolution of such source
term is visualized revealing that the events of highest activity are associated with the processes of
vortex-ring pairing and vortex-ring disruption for the circular jet, and with the decay of streamwise
instabilities and the formation of C-shaped structures for the chevron case.
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