A PIV study of the laminar axisymmetric sudden expansion flow

Hammad, Khaled J.; Otugen, M. V.; Arık, E.

doi:10.1007/s003480050288

Cited by 54 publications

(33 citation statements)

References 10 publications

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“…zr is the non-dimensional length of the recirculation region in the pipe for Re = 1000. (Cantwell et al 2010), (△) and (▽) corresponds to experimental result (Latornell & Pollard 1986;Hammad et al 1999) 2zr = 0.088 Re and 2zr = 0.096Re respectively for sudden expansions.…”

Section: Methodsmentioning

confidence: 99%

“…In the axisymmetric sudden-expansion pipe flow, bifurcations of flow patterns have been studied experimentally (Sreenivasan & Strykowski 1983;Latornell & Pollard 1986;Hammad et al 1999;Mullin et al 2009) and numerically (Sanmiguel-Rojas et al 2010;Sanmiguel-Rojas & Mullin 2012). In these studies, flow separation after the expansion and reattachment downstream leads to the formation of a recirculation region near the wall.…”

Section: Introductionmentioning

confidence: 99%

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Localised turbulence in a circular pipe flow with gradual expansion

2015

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We report the results of three-dimensional direct numerical simulations for incompressible viscous fluid in a circular pipe flow with a gradual expansion. At the inlet, a parabolic velocity profile is applied together with a constant finite amplitude perturbation to represent experimental imperfections. Initially, at low Reynolds number, the solution is steady. As the Reynolds number is increased, the length of the recirculation region near the wall grows linearly. Then, at a critical Reynolds number, a symmetry-breaking bifurcation occurs, where linear growth of asymmetry is observed. Near the point of transition to turbulence, the flow experiences oscillations due to a shear layer instability for a narrow range of Reynolds numbers. At higher Reynolds numbers the recirculation region breaks into a turbulent state that remains spatially localised and unchanged when the perturbation is removed from the flow. Spatial correlation analysis suggests that the localised turbulence in the gradual expansion possess a different flow structure from the turbulent puff of uniform pipe flow.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Localised turbulence in a circular pipe flow with gradual expansion

2015

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“…walls and deviates from free jet predictions. While some previous mathematical analyses [11] have investigated flow behavior, they have not presented compact correlations to predict the flow, while other experimental investigations [12] did not investigate large expansion ratios. The transition regions identified in this work include the location where the jet begins to deviate from the linear behavior associated with a free jet, the location where the flow reattaches to the confinement wall, known as the reattachment length, and the location where flow in the confinement becomes fully developed.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Behavior of Confined Laminar Round Jets

Landfried

Jana

Kimber

2012

Volume 1: Symposia, Parts a and B

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Confined laminar fluid jets have many practical applications in industry. Several examples include expansions in pipes and flow of gas into a large plenum. While much consideration has been given experimentally to heat transfer and pressure gradients within the confinement, little attention has been paid to quantify the velocity profiles and transitions between various flow behaviours. Using a finite volume CFD code, OpenFOAM ®, the Navier-Stokes equations were solved for varying expansion ratio, 1/ε = renclosure/rj, and varying Reynolds numbers. In the present analysis, Reynolds number based on the inlet jet diameter is varied from 30 to 70, well within the accepted range for laminar jet behavior. The expansion ratio, 1/ε is varied from 20–200. Of primary focus in the current study are compact correlations for the jet centreline velocity as a function of jet Reynolds number, Rej and expansion ratio. Similar functional dependences for the “linear” decay region of the jet, and the location of the stagnation point on the enclosure wall, are also investigated. These are all important features of the global flow field for the confined jet. Results suggest that initially, the flow characteristics are identical to a free jet. At some downstream location, the presence of the enclosure is felt by the jet and deviations begin to be seen from free jet behavior. This transition region continues until at a sufficiently large downstream location, the flow becomes fully developed, internal Poiseuille flow. In this paper, we analyse these transition regions and offer explanations and practical correlations to successfully predict the important flow physics that occur between free jet behavior and Poiseuille flow. Key dimensionless parameters are identified, the magnitude of which can be used to classify the flow conditions.

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“…The normalised error in the mass flux is therefore equal to 4 × 10 −3 , which is acceptable relative to the spatial discretisation, and it does not have a significant impact on the simulation. In Figure 9 the streamlines obtained from the stream function are compared with the experimental results presented in Hammad et al [21] and a finite volume solution using Code_Saturne [22]. The calculation of the stream function Ψ from a velocity field can be performed using different methods and can provide insight into sources of disagreement with the experimental values.…”

Section: Rapidly Expanding Pipementioning

confidence: 99%

“…The geometrical parameters are chosen to correspond to one of the experiments presented by Hammad et al [21]: Figure 8 shows the horizontal velocity and density profiles at the inlet and outlet. As can be seen the velocity profile at the outlet is very close to the Poiseuille flow.…”

Section: Rapidly Expanding Pipementioning

confidence: 99%

Unsteady open boundaries for SPH using semi-analytical conditions and Riemann solver in 2D

Ferrand

Joly

Kassiotis

et al. 2017

Computer Physics Communications

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Due to the Lagrangian nature of SPH, treating inlet/outlet boundaries (that are intrinsically Eulerian) is a challenging issue. An extension to the Unified SemiAnalytical boundary conditions is presented to deal with unsteady open boundaries in confined and free-surface flows. The presented method uses Riemann invariants to calculate flow properties near the open boundaries, thus allowing the possibility to treat complex shapes. Furthermore, details are presented for a parallel implementation of this method, including particle creation and deletion, updating properties of vertices and segments, and additional constraints on the time step. Simple validation cases are then displayed to illustrate the performance of the proposed method as well as the ability to deal with complex problems such as generation of water waves and free outlets.

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A PIV study of the laminar axisymmetric sudden expansion flow

Cited by 54 publications

References 10 publications

Localised turbulence in a circular pipe flow with gradual expansion

Localised turbulence in a circular pipe flow with gradual expansion

Characterization of the Behavior of Confined Laminar Round Jets

Unsteady open boundaries for SPH using semi-analytical conditions and Riemann solver in 2D

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