Synergism of flow and noise control technologies

End-plate for noise-by-flow control in axial fans

“…During the last two decades, noise control has emerged as a new research field [12,13]. The scholars working in this field have proposed numerous noise reduction strategies that may be broadly categorised as passive, active or reactive.…”

A Critical Review of Stall Control Techniques in Industrial Fans

“…We typically derive flow control methodologies from an understanding of the relevant mechanisms or processes [48] and we can categorise them according to how one utilises flow control [49]. This can be (i) active, entailing flow control; or (ii) passive, entailing a flow management.…”

Synergistic Noise-By-Flow Control Design of Blade-Tip in Axial Fans: Experimental Investigation

“…Kameier and Neise (1997) highlighted that, in addition to the broadband influence, tip leakage flows could be responsible for narrowband tones at frequencies below the blade passing frequency in coincidence with a tip vortex separation. During the last decades, noise control has emerged as a new field of research as the literature demonstrates (Gad-el-Hak, 2000;Joslin et al, 2005), and scholars have proposed noise reduction strategy classifications, which distinguish between passive, active and reactive devices. A number of research programmes envisioned designs tailored to a synergistic noise and flow control by incorporating structural (passive) or flow (active) technologies in synergy with those mechanisms leading to a reduction of the noise sources' effectiveness.…”

“…Two textbook examples of this include: i) the chevron mixer for jet noise reduction among the structural-passive technology (Saiyed et al, 2000), and ii) the trailing edge blowing in turbomachinery noise suppression in the active-flow technology family (Brookfield & Waitz, 2000). According to Thomas et al (2002) and Joslin et al (2005), we can base a possible classification of flow and noise control technologies on the nature of the linkage between the underlying flow physics and the noise generation mechanisms. According to the exploitation of the flow control, the overall effect on performance or noise can be productive, due to the direct or indirect linkages, or counterproductive (Joslin et al, 2005).…”

“…According to Thomas et al (2002) and Joslin et al (2005), we can base a possible classification of flow and noise control technologies on the nature of the linkage between the underlying flow physics and the noise generation mechanisms. According to the exploitation of the flow control, the overall effect on performance or noise can be productive, due to the direct or indirect linkages, or counterproductive (Joslin et al, 2005). In the framework of industrial turbomachinery, the noise control techniques documented in the open literature are mostly passive systems.…”