The role of shape and relative submergence on the structure of wakes of low-aspect-ratio wall-mounted bodies

Hajimirzaie, Seyed M.; Wojcik, Craig; Buchholz, James

doi:10.1007/s00348-012-1406-1

Cited by 39 publications

(40 citation statements)

References 44 publications

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“…This flow motion induces the enclosed wake to feature a clockwise rotation that is well indicated by the streamlines in The presence of a horizontal roller for the submerged cone has also been observed for the submerged cylinder, cuboid and ellipsoid flow. 1,11,17,21,42 This upward flow region is significantly greater compared to that observed in the cylinder flow 1,21 due to the cone's geometry and inclined leeward face.…”

Section: B Time-averaged Velocity Fieldmentioning

confidence: 86%

“…This is in agreement with studies on flow around ellipsoidal bodies, particularly the downstream tilting of arch vortices observed for an ellipsoid when its longer axis is aligned in the spanwise direction. 17 Figure 10(a) shows that the coherence of the arch vortex is lost before the onset of the von Karman vortex shedding and that the horizontal extension of the KV structures is proportional to the diameter of the cone at its basement whilst they are vertically distributed over the whole water depth. Thus, despite the cone's height being lower than the water surface elevation for the SS case, the von Karman vortices expand over the whole water depth constrained by the presence of the free-surface layer.…”

Section: Instantaneous Flow Structuresmentioning

confidence: 99%

“…16,21,23 For a submerged ellipsoid, the strength of the base vortices reduces with increasing submergence, while the strength of the tip vortices is not affected by submergence. 17 However, the strength of the von Karmantype vortex shedding was highly influenced by the degree of submergence with a wider wake region and stronger periodic shedding taking place for lower submergences. 24 In contrast, increasing submergence the region narrows with the eventual termination of the shedding.…”

Section: Introductionmentioning

confidence: 99%

“…Such arch vortices have been observed for a number of object geometries, including cylinders, hemispheres, ellipsoids, and cubes. 1,[15][16][17] For the case of cylinders, it has been postulated that the arch vortex is the result of the two tip vortices combining with the vortex sheets shedding from the sides of the obstacle. 13,18,19 The arch vortex is formed independently of whether the vertical vortices are shed simultaneously from each side of the cylinder or shed off each alternate side as in "von Karman-type" shedding.…”

Section: Introductionmentioning

confidence: 99%

“…An ellipsoid with a longer length in the streamwise direction compared to the transverse direction results in more dominant tip structures, while base structures were more dominant in the transverse ellipsoid. 17 Other studies have examined the ratio of flow depth (H) to object height H h (also termed submergence or relative submergence) with the majority of research focusing on deeper flows usually conducted in wind tunnels. For hemispherical and cylindrical objects, two distinct wake types are observed, both dependent on submergence: a wake-bubble with downstream vortex shedding for slightly submerged and emergent objects 21 and an enclosed recirculation region with no shedding for moderate to deeply submerged objects.…”

Section: Introductionmentioning

confidence: 99%

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Large-eddy simulation of shallow turbulent wakes behind a conical island

et al. 2017

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Large-Eddy Simulations (LESs) and experiments were employed to study the influence of water depth on the hydrodynamics in the wake of a conical island for emergent, shallow, and deeply submerged conditions. The Reynolds numbers based on the island’s base diameter for these conditions range from 6500 to 8125. LES results from the two shallower conditions were validated against experimental measurements from an open channel flume and captured the characteristic flow structures around the cone, including the attached recirculation region, vortex shedding, and separated shear layers. The wake was impacted by the transition from emergent to shallow submerged flow conditions with more subtle changes in time-averaged velocity and instantaneous flow structures when the submergence increases further. Despite differences in the breakdown of the separated shear layers, vortex shedding, and the upward flow region on the leeward face (once the cone’s apex is submerged), similar flow structures to cylinder flow were observed. These include an arch vortex tilted in the downstream direction and von Karman vortices in the far-wake. Spectra of velocity time series and the drag coefficient indicated that the vortex shedding was constrained by the overtopping flow layer, and thus the shedding frequency decreased as the cone’s apex became submerged. Finally, the generalised flow structures in the wake of a submerged conical body are outlined.

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