Abstract
Cylindrical bodies in uniform flows can be coated with a porous medium as a passive flow and noise control method in an effort to reduce the acoustic effects of vortex shedding. To date, the employed open-cell porous materials typically possess a randomized internal structure. This paper presents the design and validation of a novel 3-D printed structured porous coated cylinder that has significant flexibility, in that the porosity and pores per inch of the porous coating can be modified independently and relatively easily. The performance of the structured porous coating design is compared against porous polyurethane and metal foam with the same coating dimensions and similar pores per inch and porosity via an experimental acoustic investigation, revealing strong similarity in the passive noise control performance of each material type. A numerical comparison illustrates the similarities of the wake structure of the 3-D printed porous coated cylinder to an equivalent Darcy–Forchheimer model simulation that represents a randomized internal porous structure. The performance similarities of these different porous material types indicate that a structured porous geometry can be used to understand the internal flow behavior of the porous medium responsible for reducing the cylinder vortex shedding tone that is otherwise extremely difficult or impossible with typical randomized porous structures. Moreover, significant potential exists for the porous structure to be further optimized or smartly tailored by architectural design for different control purposes, coating geometries and dimensions, and working conditions.
Highlights
Passive flow control methods have become increasingly important and popular in commercial and industrial applications that display bluff body aeroacoustic noise
The investigation of porous coated cylinders is of specific interest, as the cylinder can pose as a simplistic representation of typical noisy engineering components due to aeroacoustic interaction, such as an aircraft landing gear [1] and parts of high speed train pantographs [2]
The intention of these results is to show the similarity in recorded acoustic measurements and flow behavior between the SPCC and other Porous Coated Cylinders (PCCs) types, thereby validating the SPCC as an alternative to common porous materials for passive flow and noise control
Summary
Passive flow control methods have become increasingly important and popular in commercial and industrial applications that display bluff body aeroacoustic noise. Porous coatings of bluff bodies is a relatively new method of passive flow control. Vortex shedding control of a cylinder was investigated by Zradkovich [3]. Who applied a metal foam coating to a cylinder surface to minimize the effects of vortex shedding and claimed that a prolonged wake could minimize the lift and drag force fluctuations acting on the cylinder. Doppler Anemometry a more stabilized wake and a significant reduction in pressure drag coefficient. Ruck et al [6] and Klausmann and Ruck [7] experimentally investigated the effects of replacing a segment of the leeward side of a cylinder with a porous medium, revealing significant drag reduction
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