Numerical analysis of the correlation between fluid dynamic modes and hydrodynamic noise in flows around a three-dimensional circular cylinder

The flow around a circular cylinder for Re = 1000 is characterized by flow separation and Karman vortex street. The typical flow features can be captured to study the correlation between fluid fields and sound fields. In this paper, the three-dimensional circular cylinder is taken as the research object, and the probes of surface fluctuating pressure and far field sound pressure are arranged every 10°. The directional diagram and the coherence of fluctuating pressure and sound pressure are analyzed. The relationship between the flow mode and hydrodynamic noise is studied by using dynamic mode decomposition (DMD). The characteristics of the dipole and quadrupole sound source term of a long span cylinder are studied. The results show that at the angles between 30°–120° and 190°–350°, the fluctuating pressure contributes more to the generation of dipole sounds. The quadrupole sound source shows three-dimensional effects, which is more obvious in a cylinder with large spanwise length.