Particulars of the cross- and spanwise near-wake development of a short Semicircular-section Shell, through the TransitionRe-range (60 ≤Re ≤ 600)

Abstract

Within the fundamental context of quasi-2D bluff-body near-wake investigation, we analyse the way the initial wake vortices (primary and secondary vortices) form and develop with time behind a short (5.2:1) cylindrical semicircular shell (hollow at the back), after an impulsive start in translation. The study includes the transition regime and non-usual cross-sectional shapes. The structure of the vortices is examined by means of precise visualizations both in the mid-cross and mid-span planes. The particulars induced by the hollow face are deduced from a comparison with the cases of analogous solid cylinders and more particularly with the full semicircular cylinder (Boisaubert et al., 1996; Coutanceau et aI.,1998).The crosswise analysis shows that, except some fundamental difference at the separation initiation and some differences in details, a similar development ofthe Benard-Karman-vortices is observed, thus:-the regime ofthe occurring structures changes beyond the first phase of development (i.e. t"~6) when Reynolds number is passing through a critical value Re, (here 120 :s; Re, :s; 140)-Kelvin-Hehnholtz instabilities are detected for Re = 600 in the rolled-up separated shear layers originating from the sharp body-edges. On the contrary, the spanwise analysis reveals that the hollow face plays an important role in the time-development of the induced body-end three-dimensionalities (end-vortices and opposite spanwise currents) and intrinsic three-dimensionalities respectively. Thus, as opposed to solid bodies similarly limited in span, the emergence of clear patterns of secondary Taylor-Gortler-like vortices in the near wake have been experimentally proved for the first time when Re passes beyond the transition value of Re, '" 200. The consequence on the global structure of the flow is deduced.

CFD analysis of power-law fluid flow and heat transfer around a confined semi-circular cylinder

“…They obtained the corresponding Strouhal number as 0.166, which was 7% larger than that of a circular cylinder at the corresponding transition. Coutanceau et al [16] explained not only the way of formation of the initial wake vortices (primary and secondary vortices), but also their development with time behind a short cylindrical semi-circular shell. They reported about regime where structure changes occurred beyond the first phase of development when Re was between 120 and 140.…”

Momentum and heat transfer characteristics of a semi-circular cylinder immersed in power-law fluids in the steady flow regime

“…It also captures some aspects of novel impeller designs used in the mixing of viscous fluids. In spite of these potential applications, this flow configuration has received very little systematic attention to date, e.g., see [22][23][24][25][26]. The available scant literature has been reviewed recently [27].…”

Fluid flow and heat transfer around a confined semi-circular cylinder: Onset of vortex shedding and effects of Reynolds and Prandtl numbers

“…This motivated us to examine the confined forced convection heat transfer from a semi-circular cylinder in the unsteady regime (or at intermediate Re). On the other hand, extensive numerical/experimental literature is available on the forced flow and heat transfer around a semi-circular cylinder in the unconfined domain [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Among these studies, Kiya and Arie 63 [9], Boisaubert et al [10], Coutanceau et al [11], Sophy et al [12], Koide et al [13], Koide et al [14], Chandra heat capacity of fluid (J kg…”