Effects of viscoelastic fluid on noise reduction of the flow over a circular cylinder

Abstract

Viscoelastic fluid can suppress instabilities of vortices around a circular cylinder, and has a wide application prospect in flow noise reduction. The effects of elasticity and the maximum polymer extensibility of dilute polymer solution on the noise reduction of flow around a circular cylinder were investigated. FENE−P model was used to simulate flow noise of two-dimensional flow through two different sound source extraction methods with Reynolds number of 100, Weissenberg number of 0 to 40, and the maximum polymer extensibility of 10 to 100. Results show that viscoelastic fluid can inhibit the formation of vortices, reduce the fluid pulsation around cylinder, and reduce intensity of dipole sound source on cylindrical surface. With appropriate maximum polymer extensibility, flow noise is particularly reduced, and elasticity will enhance the noise reduction effect. On condition that the Weissenberg number remains unchanged, a moderate increase in the maximum polymer extensibility can further reduce dipole intensity as well as drag of cylindrical surface, and flow noise will be further reduced. However, if the maximum extensibility of the polymer is too high, solid-like behavior will occur around the cylinder, greatly increasing drag and elastic stress and creating a new dipole around the fluid wall. Finally, noise increases. This study analyses the influence of various parameters in a viscoelastic fluid on noise and provides an idea with promising applications for flow noise reduction.