A coaxial jet was actively controlled by a MEMS-fabricated micro flap actuator nozzle. The effect ofdifferent control modes on secondary azimuthal instabilities and the evolution of streamwise vorticeswere investigated by applying stereoscopic PIV to the cross-stream plane of the jet. Forcing withnon-symmetric modes, in particular the least-stable helical mode, accelerates the evolution of thestreamwise vortices through the enhancement of azimuthal instabilities. Although forcing is appliedto the outer shear layer of the outer jet, the control effect is most pronounced in the inner shear layerof the inner jet. Unlike in the natural jet, streamwise vortices appear in the inner shear layer of thecontrolled jet. For forcing with the fundamental axisymmetric mode, a Strouhal number of the orderof unity maximise the azimuthal instabilities and hence the counts of the streamwise vortices. Thepresent result is in accordance with our previous experimental findings in the longitudinal plane,where the evolution of the primary vortices and mixing between the inner and the outer jets wereexamined through 2D-PIV and PLIF (Kurimoto et al., 2004, Active control of coaxial jet mixing witharrayed micro actuators. Transactions of the Japanese Society of Mechanical Engineers, pp. 31–38.)This emphasises the connection between primary and streamwise vortices and their significance in themixing enhancement process. It is also found that the azimuthal wavelength under the present controlscheme is almost the same as that of the natural jet and independent of the streamwise position.
☆双向各三束光片照明,360° 全方位成像;☆光片参数可变,适用于各种样品;☆简单易用的样品腔,可对活体动物和透明组织进行成像;☆可在水溶性缓冲液和透明溶剂中成像,并对不用溶剂进行折射率修正;☆水平方向光路的动态聚焦,带来佳的分辨率;☆超大工作距离,支持大样品体积10 x 10 x 10mm;☆放大倍率可在1.26x至12.6x调整。