Effect of external disturbances on the spreading rate of a plane turbulent jet

Bradshaw, P.

doi:10.1017/s0022112077002493

Cited by 36 publications

(14 citation statements)

References 1 publication

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“…The mean velocity and fluctuation intensity profiles at and near the exit of the jet were checked to be axisymmetric. The jet discharges through the center of a 30 cm diameter disc into a large laboratory (15m x 30m x 3.5m) with controlled temperature, humidity, and traffic, so that the flow is essentially free from significant ambient recirculation and disturbances (Bradshaw 1977). The flow facility is schematically shown in the long-time space-time correlation is defined as:…”

Section: Apparatus and Proceduresmentioning

confidence: 99%

Search for Large-Scale Coherent Structures in the Nearly Self-Preserving Region of a Turbulent Axisymmetric Jet

Tso

Kovásznay

Hussain

1981

Journal of Fluids Engineering

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In an attempt to explore the existence of large-scale coherent structures in the nearly self-preserving region of an axisymmetric free air jet, a 2.54 cm air jet at a Reynolds number ReD = 6.8 × 104 has been investigated for x/D≥40 via both long and short time-averaged space-time correlation measurements. Conventional space-time correlation data with probe separations in the stream wise direction by as much as 25 diameters suggest the passage of large-scale organized structures. The radial extent of these structures is about one local jet diameter, and the azimuthal extent is about a quadrant of the cross-section. Recurring quasi-periodic patterns are observed in the time series of short time-averaged correlations between longitudinal velocity fluctuations obtained with two arrays of hot-wires separated in the streamwise direction. These orderly patterns provide direct evidence for the existence of these structures. Quantitative details of these structures are now being investigated.

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Section: Apparatus and Proceduresmentioning

confidence: 99%

Search for Large-Scale Coherent Structures in the Nearly Self-Preserving Region of a Turbulent Axisymmetric Jet

Tso

Kovásznay

Hussain

1981

Journal of Fluids Engineering

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“…Of the few comparative experimental studies undertaken between free and impinging (non-swirling) jets, those in axisymmetric configurations by Donaldson and co-workers [81,82], Popiel and Trass [83] and Looney and Walsh [84] are, however, derived at varied conditions, which makes it difficult to draw summative observations on the fundamental effects of jet impingement, and swirl, on jet development. Contributing to this challenging task is the variety of inlet and boundary conditions employed [84][85][86], many of which are also not completely reported to facilitate modelling or be subject to secondary flow influences, such as recirculation arising from the unique characteristics of the particular apparatus used [81].…”

Section: Introductionmentioning

confidence: 99%

The effect of inflow conditions on the development of non-swirling versus swirling impinging turbulent jets

2015

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“…Studies undertaken over many years [12][13][14][15][16] have shown that the downstream development of a jet depends on the flow at the jet origin, often termed initial conditions. The analytical work of George 12 and experimental assessments on round and plane jets ͑e.g., Refs.…”

Section: Introductionmentioning

confidence: 99%

The influence of Reynolds number on a plane jet

2008

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The present study systematically investigates through experiments the influence of Reynolds number on a plane jet issuing from a radially contoured, rectangular slot nozzle of large aspect ratio. Detailed velocity measurements were performed for a jet exit Reynolds number spanning the range 1500≤Reh≤16 500, where Reh≡Ubh/υ with Ub as the momentum-averaged exit mean velocity, h as the slot height, and υ as the kinematic viscosity. Additional centerline measurements were also performed for jets from two different nozzles in the same facility to achieve Reh=57 500. All measurements were conducted using single hot-wire anemometry to an axial distance (x) of x≤160h. These measurements revealed a significant dependence of the exit and the downstream flows on Reh despite all exit velocity profiles closely approximating a “top-hat” shape. The effect of Reh on both the mean and turbulent fields is substantial for Reh<10 000 but becomes weaker with increasing Reh. The length of the jet’s potential core, initial primary-vortex shedding frequency, and far-field rates of decay and spread all depend on Reh. The local Reynolds number, Rey0.5≡2Ucy0.5/υ, where Uc and y0.5 are the local centerline velocity and half-width, respectively, are found to scale as Rey0.5∼x1/2. It is also shown that, for Reh≥1500, self-preserving relations of both the turbulence dissipation rate (ε) and smallest scale (η), i.e., ε∼Reh3(x/h)−5/2 and η∼Reh−3/4(x/h)5/8, become valid for x/h≥20.

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Effect of external disturbances on the spreading rate of a plane turbulent jet

Abstract: The nonlinear growth of turbulent jets documented by Kotsovinos (1976) is tentatively attributed to draughts in the laboratory, caused principally by the jet itself.

Cited by 36 publications

References 1 publication

Search for Large-Scale Coherent Structures in the Nearly Self-Preserving Region of a Turbulent Axisymmetric Jet

Search for Large-Scale Coherent Structures in the Nearly Self-Preserving Region of a Turbulent Axisymmetric Jet

The effect of inflow conditions on the development of non-swirling versus swirling impinging turbulent jets

The influence of Reynolds number on a plane jet

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