Numerical study on coherent structure behind a circular disk

作者：Yang Jianzhi; Liu Minghou^*; Wu Guang; Zhong Wei; Zhang Xintai

来源：Journal of Fluids and Structures, 2014, 51: 172-188.

DOI：10.1016/j.jfluidstructs.2014.09.002

• Coherent structure
• Large eddy simulation
• Instability
• Turbulent wake
• Conditional average

A numerical study on the turbulent wake behind a circular disk of an aspect ratio 5 at Re = 10(4) is performed. Three characteristic instabilities are confirmed, including a low-frequency instability at St(L) approximate to 0.05-0.06 due to pumping motion of the recirculation region, large-scale vortex shedding at St(v) approximate to 0.14, and the shear-layer instability at St(KH) approximate to 1.4-1.6. A large waviness of the wake coherent structures is observed and further studied with the definition of the wake positions. It is suggested that the coexistence of lots of irregular helical/helical-like modes in the wake leads to the waviness. The traces of the wake positions in phase diagram could give a good description of the irregular motion of the large-scale vortex shedding location, which occurs at the same large-scale vortex shedding frequency. Two preferred states in the wake are found, which could induce two asymmetric topologies. The reflectional-symmetry-breaking regime at laminar wake is persistent in the turbulent wake and gives rise to the two asymmetric flow states. And, it is found that the coherent structure from the conditional averaging of each preferred state bears a remarkable resemblance to the wake structure at RSB mode for a low Reynolds number. Considering the topology from the conditional averaging of each preferred state and the flow visualizations at RSB mode, a spatial coherent wake structure at Re = 10(4) is then proposed.

• 出版日期2014-11
• 单位MIT; 中国科学技术大学