抄録
The flow around a torus has a complicated three-dimensional structure. We researched the spatiotemporal structure of the wake behind the torus by using an ultrasonic velocity profile (UVP) monitor, in which two kinds of tori with different diameter ratios or solidity are set in a uniform flow with zero inclination. For the wake of tori, there were two modes of flow structure according to the diameter ratio; at lower ratio, a disk mode was dominant, and at higher ratio, a ring wake mode appeared. Both flow modes are represented very well in terms of instantaneous velocity profiles in the radial direction measured by the UVP monitor. Coherent structures in these flows were investigated by the proper orthogonal decomposition (POD). Eigenfunctions in space and random coefficients in time were deduced and compared with each other in the wakes of two tori. It is indicated that the lowerorder POD modes demonstrate large-scale coherent structures.
