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

Abstract

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

Internal and Near-Wall Flow Fields of a Structured Porous Coated Cylinder and Their Role in Passive Flow and Noise Control

“…Experiments were conducted in a water tunnel in the Department of Civil Engineering and Geosciences at TU Delft, The Netherlands. This experimental method is identical to a previous investigation [13]. Tomographic PIV was used to record both the internal and near-wall flow field of the SPCC.…”

“…The typical experimentally investigated PPI range, using an MFPCC and PPCC for porous coated cylinders is from 10 PPI to 30 PPI [1,9,11,12], with significant vortex shedding tone reduction observed using 10 PPI materials [11,12]. Arcondoulis et al [10] designed a Structured Porous Coated Cylinder (SPCC) that has a clear line of sight along the cylinder span, and also from the outer SPCC surface into the internal solid cylinder thus allowing the use of tomographic PIV to obtain some insight on the internal flow fields within the porous layers [13]. They showed that the tone suppression and frequency shift were very similar to PPCCs and MFPCCs with similar porosity and PPI.…”

Structured Porous Material Design for Passive Flow and Noise Control of Cylinders in Uniform Flow

“…The largest sample (Figure 5c) has D = 96 mm and is highly transparent, as it is 3-D printed using a transparent ultraviolet curing epoxy resin. This could allow the use of Index Refraction Matching within a water tunnel facility [22] as discussed in Section 1, or tomographic PIV [20] to investigate the internal flow field of a PCC. To 3-D print a customized randomized porous structure, let alone a highly transparent one, would present a significant challenge.…”

“…Despite these numerical simulations, there are no experimental data to verify these results. Understanding important fundamental flow characteristics, such as spanwise coherence length [12], development of the boundary layer within the porous structure [19,20] and regions of instabilities within the cylinder wake [21] will help enable the design of improved or optimized porous materials not only for cylinders, but for the bluff bodies that they represent [1,2,4].…”

“…By adding saline-based chemicals into the water, the refractive indices of the material body and the fluid can be matched, thereby making the body totally transparent. Then by using planar-PIV or tomographic PIV of a transparent cylinder [20], the internal flow field of the porous coated cylinder can be recorded. While this method is attractive, the material used for the porous coated cylinder must be highly transparent and therefore either CNC-machined or 3-D printed, thereby eliminating the use of readily available materials possessing a randomized internal porous structure.…”