Effect of natural ventilation on the boundary layer separation and near-wake vortex shedding characteristics of a sphere

Passive control of flow structure interaction between a sphere and free-surface

“…However, it is clear that there is only a small change on the flow patterns in the presence of ventilation for h/D!1.0. On the other hand, Suryanarayana and Prabhu [17] stated that the observed drag reduction of wake unsteadiness, presumably caused by the stabilization/weakening of the randomly rotating 3-D vortical structure of the smooth sphere, which was also observed in the present study. As seen in Figure 4, secondary vortices forms in the wake region due to jet flow through the vent.…”

“…It may be noted that any reduction in the wake unsteadiness may be expected to result in drag reduction. The modified flow structure of the near wake of the vented sphere may be characterized by a pair of counter-rotating ring vortices, which have the effect of aerodynamically streamlining the sphere as expressed by Suryanarayana and Prabhu [17]. As pointed by Suryanarayana and Prabhu [17], the effect of natural ventilation can be categorized in two broad regimes as weak and strong interaction regimes.…”

Comparison of Flow Characteristics of Different Sphere Geometries Under the Free Surface Effect

“…In the second and third columns of figure 3, instantaneous vector field and corresponding vorticity patterns are shown. The modified flow structure of the near wake of the vented sphere may be characterized by a pair of counter-rotating ring vortices, which have the effect of aerodynamically streamlining the sphere as expressed by Suryanarayana and Prabhu [19]. For all sphere models, wake structure has complicated and very wavy wake.…”

“…Control of flow structure around a sphere for various active and passive methods was studied by Suryanarayana and Prabhu (2000), Suryanarayana and Meier (1995), Suryanarayana et al (1993), Ozgoren et al(2011bOzgoren et al( , 2011c, Kim and Durbin (1988), Kiya (1988), Owen and Bearman (1988), Mehta (1985) and further investigations cited therein [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”

Turbulent shear flow downstream of a sphere with and without an o-ring located over a plane boundary

“…The cause of this rapid drag-coefficient reduction is the existence of small separation bubble(s) above the surface. Suryanarayana and Meier (1995) and Suryanarayana & Prabhu (2000) investigated the ventilation effects on the flow characteristics in the wake of a sphere [5][6]. They recorded that the ventilation decreases the drag coefficient for Reynolds number higher than critical value while it is less effect on the flow structure at intermediate Reynolds numbers.…”