Experimental control of vortex breakdown by density effects

Ismadi, Mohd Zulhilmi Paiz; Meunier, Patrice; Fouras, Andreas; Hourigan, Kerry

doi:10.1063/1.3560386

Cited by 18 publications

(22 citation statements)

References 37 publications

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“…One review of the progress made in breakdown control is Mitchell and Delery, 12 and research into control methods is continuing. [13][14][15][16][17] Despite the significant control demonstrated however, these methods appear not to have contributed to breakdown control in practice. The current solution for the F/A-18, for instance, is the placement of a vortex generator on the surface of the leading-edge extension to divert the vortex outboard of the vertical stabilizers, where breakdown when it does occur can do less harm.…”

Section: Introductionmentioning

confidence: 64%

A study of the geometry and parameter dependence of vortex breakdown

2015

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The types of vortex breakdown observed in the torsionally driven cylinder (TDC) flow and in the flow through an open-ended pipe are compared. The connection between the various breakdown types is specifically addressed, and the differences in manifestation of breakdown are attributed to the different Reynolds number regimes involved. Here, in both cases, the Reynolds number is based on quantities associated with the vortex core immediately upstream of breakdown, rather than the more geometry-specific Reynolds number defined in the previous work. Thus, the relationship between the TDC flow and the flows observed in other, more open geometries, is clarified. The predominantly asymmetric breakdown observed in open high Reynolds number flows is replaced by a closed bubble form with decreasing Reynolds number in the TDC. Three-dimensional numerical simulations support this interpretation, showing that the 3D spiral type of breakdown is replaced by a TDC-type axisymmetric breakdown in an open pipe as the Reynolds number is reduced. The stability of the three-dimensional solutions indicates that spiral breakdown modes stabilise at lower Reynolds number, leading to an axisymmetric breakdown state as a stable evolved flow solution. C 2015 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 64%

A study of the geometry and parameter dependence of vortex breakdown

2015

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“…This method is considered to be accurate and relatively fast (about 0.5 min). The absolute accuracy of the instrument is said to be 0.001 g/cm 3 , but apparently, it is higher (Ismadi, Meunier, Fouras, & Hourigan, ). After many (20) measurements, we conclude that the deviation is merely 0.0001 g/cm 3 .…”

Section: Methodsmentioning

confidence: 99%

Discharge estimation of submarine springs in the Dead Sea based on velocity or density measurements in proximity to the water surface

Munwes

Geyer

Katoshevski

et al. 2019

Hydrological Processes

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The Dead Sea is a closed lake, the water level of which is lowering at an alarming rate of about 1 m/year. Factors difficult to determine in its water balance are evaporation and groundwater inflow, some of which emanate as submarine groundwater discharge. A vertical buoyant jet generated by the difference in densities between the groundwater and the Dead Sea brine forms at submarine spring outlets. To characterize this flow field and to determine its volumetric discharge, a system was developed to measure the velocity and density of the ascending submarine groundwater across the center of the stream along several horizontal sections and equidistant depths while divers sampled the spring. This was also undertaken on an artificial submarine spring with a known discharge to determine the quality of the measurements and the accuracy of the method. The underwater widening of the flow is linear and independent of the volumetric spring discharge. The temperature of the Dead Sea brine at lower layers primarily determines the temperature of the surface of the upwelling, produced above the jet flow, as the origin of the main mass of water in the submarine jet flow is Dead Sea brine. Based on the measurements, a model is presented to evaluate the distribution of velocity and solute density in the flow field of an emanating buoyant jet. This model allows the calculation of the volumetric submarine discharge, merely requiring either the maximum flow velocity or the minimal density at a given depth.

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“…Second, the successful formation of vortex breakdowns was described when a fluid with smaller density was injected into the water inside a cylinder that had a rotating top lid. 33 These authors observed that a small density difference of 0.02% halved the critical Reynolds number for the appearance of vortex breakdown, a fact that was not averted either by using a lighter fluid. For density differences larger than 0.03%, they also found that the lighter fluid pierced through the bubble, which resulted in a new structure of vortex breakdown.…”

Section: Introductionmentioning

confidence: 95%

Experimental study of rotating Hagen-Poiseuille flow discharging into a 1:8 sudden expansion

et al. 2015

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In this paper, we present experimental evidence for the five different states that result from rotating Hagen-Poiseuille flow when it discharges into a 1:8 sudden expansion, namely: stable, convectively unstable, unstable shear layer, stable and unstable vortex breakdowns. Sanmiguel-Rojas et al. [“Three-dimensional structure of confined swirling jets at moderately large Reynolds numbers,” Phys. Fluids 20, 044104 (2008)] numerically predicted four of these five states and mapped the transition from one state to another. Our main objective is to study the onset of instabilities and vortex breakdown in these states experimentally. For this purpose, we visualize the flow at the inlet of the expansion for several values of moderately large Reynolds numbers, Re, and of swirl parameters, S. We analyze the inner region of the state that corresponds to the unstable shear layer in the sudden expansion and find two different states that share the same character, although they have different non-dimensional frequencies. The first relates to an oscillating structure near the axis, which arises at a small value of the swirl parameter, as well as to a generation of vortices that move downstream. The second shows, for greater values of the swirl parameter, vortices interacting with the boundary layer located on the wall of the static container that is perpendicular to the flow direction. In addition, we find a transition from stable to unstable vortex breakdown when perturbations become absolutely unstable inside the rotating pipe flow. Therefore, the most remarkable experimental finding is a new state, namely, unstable or transient vortex breakdown that takes place for the same pair of values (Rea, Sa) at which the onset of the absolute instability curve appears and intersects the region of stable vortex breakdown.

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Experimental control of vortex breakdown by density effects

Cited by 18 publications

References 37 publications

A study of the geometry and parameter dependence of vortex breakdown

A study of the geometry and parameter dependence of vortex breakdown

Discharge estimation of submarine springs in the Dead Sea based on velocity or density measurements in proximity to the water surface

Experimental study of rotating Hagen-Poiseuille flow discharging into a 1:8 sudden expansion

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