漩涡抖动

采用德国LaVision公司的软件平台和四台Imager SX 4M型CCD相机。构成一套层析PIV处理系统。并利用这样的系统对受到漩涡诱导振动（VIV）影响的系留球体尾流进行了Tomo-PIV测量。

The trajectory of the tip vortex of a reduced-scale, 1 m diameter, four-bladed rotor during hoveris studied using vortex methods combined with a center of mass analysis approach. The objectiveis to develop analysis techniques capable of accurately characterizing the dynamical features of theunsteady wake produced by rotorcraft during hover, descent, ascent and forward flight conditions.Measurements of all three components of the velocity field are acquired using a stereo PIV systemsynchronized to capture up to 260◦ wake age of the vortex with 10◦ offsets during hover conditions.The nominal operating condition of the rotor is at a blade loading of CT / = 0.0645 and a rotationalspeed of 1240RPM, corresponding to Rec = 180,000. An area encompassing the 95% confidenceregion for the vortex jitter reveals a noticeable anisotropic, aperiodic pattern over all wake ages,which has not been previously observed. The principal axis of the vortex jitter also appears toalign itself perpendicular to the slipstream boundary. An accurate characterization and predictionof the trajectory of the individual tip vortices can significantly enhance the ability to design rotorsto meet specific performance targets such as reduction in fuselage vibrations, noise scattering andmaneuvering noise as well as an alleviation in the resuspension of particles during brownout

用PIV方法实验研究了5.5米宽，13.5米长水槽内浅表湍流，剪切流动中大尺度漩涡结构的产生和消失机理。