Experimental investigation of flow development and gap vortex street in an eccentric annular channel. Part 1. Overview of the flow structure

• Published in: Journal of fluid mechanics 2014-08, Vol.752, p.521-542
• Main Authors: Choueiri, George H., Tavoularis, Stavros
• Format: Article
• Language: English
• Subjects: Boundary layer; Exact sciences and technology; Flow velocity; Flows in ducts, channels, nozzles, and conduits; Fluid dynamics; Fluid mechanics; Fundamental areas of phenomenology (including applications); Instrumentation for fluid dynamics; Physics; Reynolds number; Turbulent flow; Turbulent flows, convection, and heat transfer; Wall-bounded thin shear flows
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2014.343

Flow visualization, laser Doppler velocimetry and planar and stereoscopic particle image velocimetry were used to investigate the isothermal velocity field along an eccentric annular channel with a diameter ratio of 0.5 and an eccentricity of 0.8 for a Reynolds number of 7300. Observation of the flow development has identified three distinct regions: the entrance region, the fluctuation-growth (FG) region and the rapid-mixing (RM) region. Weak quasi-periodic velocity fluctuations were first detected in the downstream part of the entrance region, and grew into very strong ones, reaching peak-to-peak amplitudes in the narrow gap that were nearly 60 % of the bulk velocity. Two mixing layers were identified on either side of the gap, which generated a street of counter rotating vortices and thorough large-scale mixing of the fluid in the channel.