On the Fluid Transport In Disk Starting Process by Lagrangian Coherent Structures
用拉格朗日相关结构研究圆盘启动过程的流体输运

Velocity distribution and vorticity distribution around vortex circulation field generated by disk starting were measured by using particle imaging velocimetry (PIV). The finite-time Lyapunov exponent (FTLE) field and the Lagrangian coherent structure (LCS) of the vortex flow were computed. Based on FTLE and LCS, following the tracks of a piece of fluid particles, fluid transport process of the vortex circulation field was analyzed. During the formation process of disk vortex circulation field, the fluid was found to be divided into three parts by the disk and the repelling-LCS. A vorticity-flux window was found through which the fluid with vorticity flows into the vortex core continuously and the unsteady boundary of the vortex ring which consists of the r-LCS leeward, the disk and the flux window was identified.