Vortical Structures in High-Reynolds-Number Jet Indicating Edgetone Oscillation

Abstract

Coherent vortical structures in a high-Reynolds number turbulent jet indicating edgetone oscillations are extracted from velocity and pressure data. Three statistical quantities are adopted as the candidate indicators of coherent structures; (i) phase-averaged vorticity, (ii) phase-averaged pressure, and (iii) phase-averaged velocity gradient tensor. All these quantities work well for extracting coherent structures in a test case of low-Reynolds number cylinder wake. However, when applied to the high-Reynolds number edgetone flow, (ii) and (iii) indicate much better performance than (i), because (i) is affected by the background time-averaged vorticity field. The advection speed of coherent structures is evaluated and compared with Powell's feedback mechanism.

Keywords

• edgetone
• coherent structure
• velocity gradient tensor
• low pressure