Experimental Investigation of Nozzle Spacing Effects on Characteristics of Round Twin Free Jets

Laban, Andrew; Aleyasin, Seyed Sobhan; Tachie, Mark F.; Koupriyanov, Mike

doi:10.1115/1.4041989

Cited by 28 publications

(16 citation statements)

References 49 publications

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“…For the experiments of Harima et al (2001), U 0 /U j = 1/(0.98S/d + 0.27) and L 0 /d = 5.6S/d − 0.31. Laban et al (2019) had performed experiments on twin round jets with S/d = 2.8, 4.1, 5.5 and 7.1 at Re = 10 000. They have provided the maximum mean velocity on the centreline and the distance to the location (U 0 and L 0 in our notation).…”

Section: Nozzle Spacing Effectsmentioning

confidence: 99%

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Development and scaling of turbulent, twin round jets

Taddesse

Mathew

2022

J. Fluid Mech.

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The velocity field of stationary, turbulent, twin round jets has been found to scale with an intrinsic velocity $U_0$ and length $L_0$ , both depending linearly on inflow plane parameters – jet velocity $U_j$ , diameter $d$ and distance between jets $S$ . Flow fields were obtained from large-eddy simulations at these conditions in two experiments: (1) at Reynolds number ${Re}=230\,000$ based on $U_j$ and $d$ , and $S/d=5$ ; and (2) at ${Re} = 25\,000$ , $S/d = 2, 4, 8$ . Each jet develops independently and then merges into a single jet with an elliptic cross-section. Downstream, the jet becomes circular after a mild overshoot. Close quantitative agreement with experiment was obtained in all cases. As the merged jets develop, fluctuation levels over a central half-width are nearly uniform and scale with the local maximum mean velocity. In all cases, the mean streamwise velocity along the centreline of the configuration, $U_c$ , rises to a peak $U_0$ at a distance $L_0$ from the inflow plane. The velocity $U_0$ decreases and $L_0$ increases with $S$ . For all nozzle spacings, a similar development was observed: $U_c/U_0$ is a function of distance $x/L_0$ only, and is essentially independent of $S/d$ and ${Re}$ . Further, these intrinsic and input quantities are connected by simple relations: $U_0 = U_j/(1.02S/d + 0.44)$ and $L_0/d = 5.58S/d - 1.16$ . The far field development of the merged jet can also be scaled with $U_0$ and $S$ , analogous to round jet scaling with $U_j$ and $d$ . Thus all twin round jets may be described by these new intrinsic scales.

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Section: Nozzle Spacing Effectsmentioning

confidence: 99%

“…Particle image velocimetry data for water jets with S/d = 1.5, 2.0, 3.0 at Re = 3300 are also available (Zang & New 2015). The most recent measurements were reported in Laban et al (2019). The round jets were at Re = 10 000 and S/d = 2.8, 4.1, 5.5, 7.1.…”

Section: Introductionmentioning

confidence: 99%

Development and scaling of turbulent, twin round jets

Taddesse

Mathew

2022

J. Fluid Mech.

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“…It is worth noting that the converging region of continuous slotted jets is characterized by the presence of a time-averaged bubble region, as opposed to continuous twin jets where no reverse flow has been detected so far, as documented by the literature review in the research paper by Laban et al [29]. Conversely, recent experimental works have demonstrated that double-orifice synthetic jets present a recirculation region between its orifices [21]; the present study, along with the findings of the cited one, can shed light on the occurrence of this inner reverse flow region for synthetic jets, also by relating phaseand time-averaged results.…”

Section: Time-averaged Resultsmentioning

confidence: 98%

Experimental and CFD Characterization of a Double-Orifice Synthetic Jet Actuator for Flow Control

Palumbo

Luca

2021

Actuators

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The paper presents a joint experimental and numerical characterization of double-orifice synthetic jet actuators for flow control. Hot-wire measurements of the flow field generated by the device into a quiescent air environment were collected. The actuation frequency was systematically varied to obtain the frequency response of the actuator; its coupled resonance frequencies were detected and the velocity amplitude was measured. Direct numerical simulations (DNS) of the flow field generated by the device were subsequently carried out at the actuation frequency maximizing the jet output. The results of a fine-meshed parametric analysis are outlined to discuss the effect of the distance between the orifices: time-averaged flow fields show that an intense jet interaction occurs for small values of the orifice spacing-to-diameter ratio; phase-averaged velocity and turbulent kinetic energy distributions allow to describe the vortex motion and merging. A novel classification of the main regions of dual synthetic jets is proposed, based on the time- and phase-averaged flow behaviour both in the near field, where two distinct jets converge, and in the far field, where an unique jet is detected. The use of three-dimensional DNS also allows to investigate the vortex merging for low values of the jet spacing. The work is intended to provide guidelines for the design of synthetic jet arrays for separation control and impinging configurations.

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“…For the formation and characteristics of a free jet, the diffuser is of key importance [23], [24], [25], [26], [27]. Studies by Hussein et al [28] or [29], or by Mi et al [30] are among the papers dedicated to the geometry of a jet generated by a round diffuser. On the other hand, examples of analyses dedicated to a rectangular nozzle include [31] or [32].…”

Section: Introductionmentioning

confidence: 99%

Pressure Distribution On A Flat Plate In The Context of The Phenomenon of The Coanda Effect Hysteresis

Skotnicka-Siepsiak

2021

Preprint

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As a result of the Coanda effect, a symmetrical free jet will flow as an asymmetrical wall jet. At the same time, at the obstacle along which the flow is observed, the wall jet generates pressure distribution. In this study, the obstacle located at the diffuser outlet is a flat plate with a variable inclination angle. The article presents results of the study on pressure distributions on a flat plate with a variable angle of inclination. What is new, however, is that the presented results of the experimental research include the influence of the Coanda effect hysteresis on the pressure distribution on the plate. The article shows how pressure distributions change on the plate depending on whether the initial angle of inclination was 0 degree and was increased gradually in the course of the experiment until a detachment of the jet flowing from the plate was observed, or the initial angle of inclination was close to 90 degrees in the primal state and as the angle of the plate inclination was decreased, the jet flowing towards the plate reached the state of attachment to the plate surface.

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Experimental Investigation of Nozzle Spacing Effects on Characteristics of Round Twin Free Jets

Cited by 28 publications

References 49 publications

Development and scaling of turbulent, twin round jets

Development and scaling of turbulent, twin round jets

Experimental and CFD Characterization of a Double-Orifice Synthetic Jet Actuator for Flow Control

Pressure Distribution On A Flat Plate In The Context of The Phenomenon of The Coanda Effect Hysteresis

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