The design and noise characteristics of a structured porous coated cylinder in uniform flow

The internal and external flow fields of a structured porous coated cylinder and implications on flow-induced noise

“…Therefore, the outer diameters are chosen to be D = 96 mm with an inner bare diameter of d = 64 mm and thus the ratio of the porous coating thickness to the bare cylinder diameter, t d, is 0.25. This t d ratio is consistent with the aeroacoustic investigation presented in Arcondoulis et al [7] and within the typical t d range of others [1,3,4,8,9,12,15,18]. It is also important to ensure that the Reynolds number range is within the range of previously published data for comparative purposes.…”

“…An iterative process of several interacting factors, such as the Reynolds number, outer diameter D and thickness-tobare-diameter ratio t d, and manufacturing limitations was conducted to design the SPCCs for a series of PIV tests in a water tunnel. The diameters of the SPCCs used for these experiments are larger than those used previously for aeroacoustic and PIV tests in air [7]. This is due to the differences in fluid medium (and required pore size to allow sufficient water-borne particles to enter the porous medium).…”

“…Arcondoulis et al [7] calculated the average quantities pertaining to porous coated cylinders obtained from the literature, as of 2017; porous cover thickness to bare cylinder diameter ratio, t d ≈ 0.22, average minimum Reynolds number of ≈ 0.8 × 10 5 and an average maximum Reynolds number of ≈ 1.5 × 10 5 . The majority of studies employ cylinders with a porous cover thickness to bare cylinder diameter ratio, t d, of 0.1 to 0.5 and within Re = 0.1 × 10 5 to 2 × 10 5 .…”

“…Arcondoulis et al [7] designed a Structured Porous Coated Cylinder (SPCC), such that a clear line of sight is possible along the cylinder span and also from the outer porous coated cylinder surface into the internal solid cylinder. They showed that the tone suppression and frequency shift were very similar to PPCCs and MFPCCs with similar porosity and PPI.…”

“…Figure 1 helps show the differences in porous structures typically used to treat cylinders for passive flow control. Due to the similar acoustic behavior of the SPCC relative to the randomized porous structures [7], it is hypothesized that the internal and external flow fields of these two different porous coated cylinder types should be very similar. The external flow field is relatively simple to compare for both cylinder types, by investigating time-averaged velocity profiles, linear instability analysis in the wake and turbulent kinetic energy levels.…”