人字形射流

采用四台高速相机构成一套时间分辨层析PIV(TomoPIV)测量，外加一台红外相机测温。研究传热和速度场的关系。研究了人字形射流撞击墙壁状态下壁温与流场的相关性

The three-dimensional behavior of flow transition in circular and 6-chevron jets at Re?000 isinvestigated with experiments conducted on a free water jet by time-resolved tomographic particleimage 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 mostpronounced phenomena observed in the near field of the circular jet. The first and second pairingamplify the axial pulsatile motion in the jet column and lead to the growth of azimuthal wavesculminating in the breakup of the vortex ring. Streamwise vortices of axial and radial vorticity areobserved in the outer region and move inward and outward under the effect of the vortex rings. Inthe 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, andcounter-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. Thethree-dimensional analysis allows quantifying the vortex stretching and tilting activity, which, for thecircular jet exit, is related to the azimuthal instabilities and the streamwise vortices connecting thevortex 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 sourceterm is visualized revealing that the events of highest activity are associated with the processes ofvortex-ring pairing and vortex-ring disruption for the circular jet, and with the decay of streamwiseinstabilities and the formation of C-shaped structures for the chevron case.

利用LaVision的DaVis8.4软件平台构成的PIV系统测量了交叉流燃油喷射的速度场，同时测量了OH基自发辐射荧光分布，研究了交叉流燃油喷射对反应射流的影响。