系留球体尾中3D3C 层析PIV检测方案(CCD相机)

智能文字提取功能测试中

ResearchGateSee discussions，stats， and author profiles for this publication at： https：//www.researchgate.net/publication/331604372 Tomo-PIV measurements in the wake of a tethered sphere undergoing VIV Article in Journal of Fluids and Structures· March 2019DOI： 10.1016/j.jfluidstructs.2019.02.003 CITATIONS READS 99 5 authors， including： Lior Eshbal Daniel Kovalev Technion-IsraelInstitute of Technology Technion-Israel Institute of Technology 4 PUBLICATIONS 16 CITATIONS 1 PUBLICATION O CITATIONS SEE PROFILE SEE PROFILE Vlad Rinsky David Greenblatt Technion-Israel Institute of Technology Technion-Israel Institute of Technology 6 PUBLICATIONS 8 CITATIONS 150 PUBLICATIONS 2，584 CITATIONS SEE PROFILE SEE PROFILE Tomo-PIV measurements of the flow field in the wake ofa tethered sphere undergoing VIV L. Eshbal， D. Kovalev， V. Rinsky， D. Greenblatt， R. van Hout* Faculty ofMechanical Engineering， Technion - Israel Institute of TechnologyTechnion city， Haifa， Israel Abstract The 3D flow field in the wake of a tethered sphere (D=6 mm，m* =7.77，L*=4.1) undergoing vortex induced vibrations (VIV) in a water tunnel， wasmeasured using tomographic particle image velocimetry (tomo-PIV). Theflow field was investigated for four different reduced velocities ranging be-tween 3.61)， at least three different modes have beenidentified6. g1. Recently several studies of VIV of a one degree of freedom，elastically mounted sphere were performed by Sareen et al.12.B，1，inconjunction with a numerical study by Rajamuni et al.1.115|. In particular，the effect of steady and oscillatory rotation of the sphere as well as its proxim-ity to a free surface was investigated. Steady rotation reduced the oscillationamplitude and led to reduced periodicity while imposed rotary oscillationboth increased as well as decreased oscillation amplitudes depending on thesphere rotation frequency. Proximity to a free surface decreased the vibra-tion amplitude while for partial submersion， it either increased or decreaseddepending on the level of submersion. By now， much is known about the transverse amplitude response of atethered sphere for a wide variety of m*. However， very little is known aboutthe 3D flow field in its wake. Numerical simulations (Re ~300) of a neutrallybuoyant tethered sphere[ho]， an elastically mounted sphere [16 as well as atransverse oscillating rotating sphere15all showed the existence of hairpinvortices in their wakes. In addition， the numerical study by Behara et al.16identified a spiral mode consisting of a pair of counter-rotating， intertwinedstreamwise vortices. Particle image velocimetry (PIV) measurements of theflow field in the wake of a tethered sphere were carried out by Govardhanand Williamson9， Sareen et al.3，114and the group of van Hout etal.2.3.1. The former performed 2D PIV measurements in atransverse plane downstream of the sphere in order to construct the spatio- temporal plots of the streamwise vorticity by assuming a convection velocity.Their results indicated a two-sided chain of trailing，“hairpin-like”vorticesthat based on dye visualizations， formed vortex rings upon pinch-off . Thevortex shedding dynamics downstream of positively and negatively buoy-ant tethered spheres was further elucidated by high-speed PIV performedin a horizontal， equatorial plane8. 111. They found planar signaturesof periodically， alternately shed hairpin vortices (412， a slowsteady rise in A3/D is observed. Compared to van Hout et al. (2010)， A3/D Figure 2： Normalized transverse rms amplitude as a function of the reduced velocity.o， present results (m*= 7.77，(m*+CA)5= 0.428)； m， van Hout eett aall.. ((2010)(m*=7.8 *+CA)=0.167) B.. VVeerrttiiccala lb abras denote extreme values are low in the range 5 关闭