Experimental investigation of the effect of endplates and sidewalls on the near field development of a smooth contraction rectangular jet

Alnahhal, M.; Cavo, A.; Romeos, Alexandros; Perrakis, Konstantinos

doi:10.1016/j.euromechflu.2011.04.003

Cited by 9 publications

(6 citation statements)

References 29 publications

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“…20 The position of the virtual origin λ * depends strongly on the range of Reynolds number and aspect ratio, with positive or negative reported values in the range −5 λ * 10. [19][20][21][22] By considering again that the local velocity u l at the bed surface is the one given by this free jet model at x * = l * and must be the same at erosion threshold for the same fluid/grains configuration whatever the distance l * , Eq. (2) with constant K implies that U J must scale as (l * + λ * ) 1/2 at threshold.…”

Section: Discussionmentioning

confidence: 99%

“…21,22 For our present configuration of rectangular jet of aspect ratio w J /b = 6 and Reynolds range (Re J ∼ o(10 3 )), K 2. 20 The position of the virtual origin λ * depends strongly on the range of Reynolds number and aspect ratio, with positive or negative reported values in the range −5 λ * 10.…”

Section: Discussionmentioning

confidence: 99%

“…These difficulties to interpret the results of the jet erosion test mainly arise from the strong non-uniform flow with a stagnation point at the bottom of the jet axis. As jet flows on solid walls have strong applications for cooling purposes, 11 the jet flow has been yet widely studied both experimentally and theoretically in both circular (3D) [12][13][14][15] or plane (2D) 14,[16][17][18] cases, with some possible strong influence of finite aspect ratio 19 or sidewalls, [20][21][22] top endwall 22 in the plane configuration, and also of porous endwall. 23,24 With the jet flow characterization, different models have been proposed for describing the time evolution of the eroded crater by an impinging jet and its asymptotic shapes at rest after the jet stops or when it comes from a dynamical equilibrium of the erosive fluid forces with the restoring gravity forces.…”

Section: Introductionmentioning

confidence: 99%

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Erosion threshold of a liquid immersed granular bed by an impinging plane liquid jet

2014

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Erosion threshold of a model granular bed by a jet in a quasi bidimensional configuration has been studied experimentally in both laminar and turbulent regimes. The jet is a liquid sheet which impinges normally a packing of immersed beads monodisperse in size and density. The erosion threshold has been characterized at different impact distances of the jet on the sediment and for different grain size and fluid viscosity. In the explored range of parameters, we show that the erosion threshold is well described by a critical inertial Shields number based on the local flow velocity at the impinging point. This has been done by a careful analysis of the different jet flow regimes taking into account the position of the virtual origin of the jet.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Erosion threshold of a liquid immersed granular bed by an impinging plane liquid jet

2014

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“…This last result has also been reported in steady, uniform flow in smooth narrow channels with the rectangular cross-section, and was attributed to the increasing influence of the secondary currents and the fluid shear stresses (reflecting the effect of eddy viscosity in turbulent flows) as the ratio between channel width to flow depth decreases [10]. Side walls (two parallel walls confining the jet at the planes of the short sides of the rectangular nozzle) have been used to force the jet to entrain only in the streamwise and lateral directions, enhancing the two-dimensionality of the flow [11,12]. It has been shown that the large-scale flow organization, for turbulent slot jets bounded by very close solid side walls, differs substantially from the slot free jet, due to the development of the shear layers on both sides (affecting the spreading of the developed jet) and secondary longitudinal vortical structures near the nozzle exit [13].…”

Section: Introductionmentioning

confidence: 99%

Experimental study on the scour due to a water jet subjected to lateral confinement

Martino

Ciani

Paterson

et al. 2019

European Journal of Mechanics - B/Fluids

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The effect of lateral confinement due to very close side walls, on erosion caused by a water jet issuing from a rectangular sluice aperture, has been studied experimentally in a narrow laboratory flume. Velocimetry (PIV) in presence of a smooth, no erodible bottom, revealed self-similar velocity profiles with the structure of a wall jet, but upward-shifted with respect to the classical two-dimensional profile. The classical definition of the Shields number was modified, to include the influence of the relative roughness and the inlet aspect ratio. This last coefficient was also relevant in the definition of a suitable length scale to account for the effect of the lateral confinement. Scour patterns in the narrow flume have also shown differences with respect to erosion by two-dimensional wall jets: the downstream mound undergoes a morphological transition, from triangular to trapezoidal, at the early stage of the scour development, and grains move downhill driven by gravity inside the granular wedge, in a regime of steady recirculation (SR). Above this regime, a digging-refilling (DR) cycle, with periods of the order of seconds, triggers at a well-defined Shields number.

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“…To the authors" knowledge, a single study refers to the influence of a flat plate imposed as a wall boundary on the exit of an axisymmetric jet (Abdel-Rahman et al 1997). Abdel-Rahman (2010) recently reviewed these measurements -the only available data relating round jets -along with the data of Alnahhal et al (2011), who studied a similar influence but in a plane turbulent jet. Although he mentioned that the use of endplates appears to restrict the mixing with ambient air providing a slower spreading rate than that of free from confinements jets, he also admitted that more systematic studies are necessary in order to clarify the behavior of the flow under this particular influence.…”

Section: Introductionmentioning

confidence: 99%

Influence of an Exit Wall Boundary on the Flow of a Circular Jet

2013

JAFM

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The flow of the axisymmetric jet constitutes a subject of research from the origins of fluid dynamics; however it remains a subject of interest due to the recent findings that denote the influence of flow and geometry conditions in configurations that diverge from the theoretical "free-jet" case. In the present study, the effect of a wall boundary produced by a circular disk of twice the jet diameter, which is imposed on the exit of the jet is investigated experimentally and numerically. Computational simulations are performed to predict the flow characteristics incorporating different turbulence models (k-ε and Reynolds Stress) and solvers (Simplec and Coupled). Supportive pressure measurements are used to evaluate the predictions within the initial region of a circular jet at two Reynolds numbers (50,000 and 65,000). The results indicate that the presence of the exit wall boundary results to the formation of recirculation zone behind the exit, which prevents the entrainment of ambient fluid. Comparing with the flow field of the free from confinement jet, it is shown that the imposition of the wall has a minor effect on the mean velocity field; it is however capable of altering the turbulent flow properties, including the normal and the Reynolds shear stresses, in the region before the establishment of the self-similarity zone.

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Experimental investigation of the effect of endplates and sidewalls on the near field development of a smooth contraction rectangular jet

Cited by 9 publications

References 29 publications

Erosion threshold of a liquid immersed granular bed by an impinging plane liquid jet

Erosion threshold of a liquid immersed granular bed by an impinging plane liquid jet

Experimental study on the scour due to a water jet subjected to lateral confinement

Influence of an Exit Wall Boundary on the Flow of a Circular Jet

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