Maps of mean gas velocity for stratified flows with and without atomization

Dykhno, L.A.; Williams, L.R.; Hanratty, Thomas J.

doi:10.1016/0301-9322(94)90039-6

Cited by 33 publications

(11 citation statements)

References 10 publications

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“…Furthermore, we observe that the secondary flow pattern is exactly the same at the 'low' and 'high' bulk Reynolds numbers, but the velocity differs in amplitude. We can note that the direction of the two large cells in the bottom is the same as that reported by Dykhno et al (1994) in horizontal gas-liquid annular flow when droplets are ejected from the liquid film.…”

Section: Results Of Single-phase Turbulent Pipe Flow (Without Particles)supporting

confidence: 66%

“…Indeed, the circumferential variation in the film thickness leads to a circumferential variation in the interface roughness, which promotes a secondary flow in the gas core Experimental study of particle-driven secondary flow in turbulent pipe flows 3 with a direction such that it exerts a drag on the film from the bottom to the top of the cross-section (Flores, Crowe & Griffith 1995), as shown in figure 1(b). However, there exists some experimental evidence that the secondary flow reverses direction when the amount of droplets in the bottom part of the gas core becomes important (Dykhno, Williams & Hanratty 1994). A satisfactory explanation has not been provided for this observation.…”

Section: Introductionmentioning

confidence: 83%

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Experimental study of particle-driven secondary flow in turbulent pipe flows

2012

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In fully developed single-phase turbulent flow in straight pipes, it is known that mean motions can occur in the plane of the pipe cross-section, when the cross-section is non-circular, or when the wall roughness is non-uniform around the circumference of a circular pipe. This phenomenon is known as secondary flow of the second kind and is associated with the anisotropy in the Reynolds stress tensor in the pipe cross-section. In this work, we show, using careful laser Doppler anemometry experiments, that secondary flow of the second kind can also be promoted by a non-uniform nonaxisymmetric particle-forcing, in a fully developed turbulent flow in a smooth circular pipe. In order to isolate the particle-forcing from other phenomena, and to prevent the occurrence of mean particle-forcing in the pipe cross-section, which could promote a different type of secondary flow (secondary flow of the first kind), we consider a simplified well-defined situation: a non-uniform distribution of particles, kept at fixed positions in the 'bottom' part of the pipe, mimicking, in a way, the particle or droplet distribution in horizontal pipe flows. Our results show that the particles modify the turbulence through 'direct' effects (associated with the wake of the particles) and 'indirect' effects (associated with the global balance of momentum and the turbulence dynamics). The resulting anisotropy in the Reynolds stress tensor is shown to promote four secondary flow cells in the pipe cross-section. We show that the secondary flow is determined by the projection of the Reynolds stress tensor onto the pipe crosssection. In particular, we show that the direction of the secondary flow is dictated by the gradients of the normal Reynolds stresses in the pipe cross-section, ∂τ rr /∂r and ∂τ θθ /∂θ . Finally, a scaling law is proposed, showing that the particle-driven secondary flow scales with the root of the mean particle-forcing in the axial direction, allowing us to estimate the magnitude of the secondary flow.

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Section: Results Of Single-phase Turbulent Pipe Flow (Without Particles)supporting

confidence: 66%

Section: Introductionmentioning

confidence: 83%

Experimental study of particle-driven secondary flow in turbulent pipe flows

2012

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“…One of the first to measure velocities in the gas phase of two-phase pipe flow were Andreussi & Persen (1987), Strand (1993), Dykhno et al (1994) and Paras et al (1998), while the liquid velocities were measured by Paras & Karabelas (1992) and Strand (1993). All these studies used single-point measurement techniques, either intrusive (Pitot tube, HWA) or non-intrusive (LDA).…”

Section: Introductionmentioning

confidence: 99%

Measurements of gravity and gravity-capillary waves in horizontal gas-liquid pipe flow using PIV in both phases

Birvalski

Tummers

Henkes

2016

International Journal of Multiphase Flow

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An experimental study was performed in stratified wavy flow of air and water through a horizontal pipe. The velocity fields in both phases were measured simultaneously using PIV and the interfacial shape was resolved using a profile capturing technique. The objective of the study was to investigate the interfacial characteristics and the velocities of the liquid and gas phases in two wave patterns: '3D small amplitude' and '2D large amplitude' waves. The wave patterns were shown to consist of gravity and gravity-capillary waves, respectively, with substantial differences in the wave characteristics and liquid velocities. Contrary to this, the effect of the waves on the gas velocities was rather similar in both wave regimes, with both wave regimes causing an increase in the velocity fluctuations close to the interface. The current measurements also produced a valuable dataset that can be used to further improve the numerical modeling of the stratified flow pattern.

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“…Jayanti et al [395] argued the tangential shear of the secondary flow to be insufficient to sustain a liquid film at the top of the circular tube, and Jayanti and Hewitt [396] even questioned the existence of secondary flows at about the same time as Flores et al [394]. However, the measurements of Flores et al [394] together with those of Dykhno et al [397] and Williams et al [398] firmly established the existence of secondary flows. Horizontal heated tubes are extensively used in once-through boilers and fluidized bed combustors.…”

Section: Secondary Field In Multiphase Turbulentmentioning

confidence: 98%

Developments in the Flow of Complex Fluids in Tubes

Siginer

2015

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Maps of mean gas velocity for stratified flows with and without atomization

Cited by 33 publications

References 10 publications

Experimental study of particle-driven secondary flow in turbulent pipe flows

Experimental study of particle-driven secondary flow in turbulent pipe flows

Measurements of gravity and gravity-capillary waves in horizontal gas-liquid pipe flow using PIV in both phases

Developments in the Flow of Complex Fluids in Tubes

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