Velocity and Reynolds stresses in a precessing jet flow

Schneider, G.; Hooper, J.D.; Musgrove, Arlene; Nathan, Graham J.; Luxton, R. E.

doi:10.1007/s003480050076

Cited by 24 publications

(17 citation statements)

References 6 publications

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“…The present study is performed using the mechanically rotating nozzle of Schneider et al, [26][27][28] shown schematically in Fig. 1.…”

Section: A Experimental Conditionsmentioning

confidence: 99%

“…In this regime the flame shape and global characteristics are similar to those obtained from comparable measurements with the fluidic PJ burners. 13 Schneider 26 and Schneider et al 27,28 have investigated the nonreacting velocity and pressure within the flow from a MPJ nozzle using both laser Doppler anemometry (LDA) and a miniature four-hole "Cobra" Pitot-tube probe. They employed a phase-averaging scheme, referenced to the phase of the nozzle, to identify flow patterns and structure for Re d = 26 600 and St p Ϸ 0.015.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, like its fluidic counterpart, this flow is extremely complex so that understanding of the turbulent mixing processes in it is still in its infancy. For example, measurements of velocity given by Schneider et al [26][27][28] were limited to the region x / d ഛ 12 and did not include energy frequency spectra nor a set of reliable highorder statistics such as skewness and flatness factors. Furthermore, previous measurements have phase averaged the flow relative to the rotation of the nozzle, rather than to the local position of the jet.…”

Section: Introductionmentioning

confidence: 99%

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Statistical analysis of the velocity field in a mechanical precessing jet flow

Nathan

2004

Physics of Fluids

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An experimental investigation of a precessing jet issuing from a mechanically rotating nozzle directed at an angle of ␣ = 45°relative to the axis of rotation is reported. Both conventional and conditional statistics of the velocity field of the jet were measured using a combined hot-wire and cold-wire (to identify any reverse flow) probe. Three distinct values (Ϸ0.005, 0.01, and 0.02) of the precession Strouhal number St p (ϵ rotation frequency ϫ nozzle diameter / jet exit bulk velocity) were used to assess the effect of varying St p . The measurements reveal that the Strouhal number in general has significant influence on the entire mixing field generated by a precessing jet. The occurrence of precession at all the Strouhal numbers of investigation produces a central recirculation zone at x ഛ 7d, where x is a distance measured from the rotating nozzle exit. A critical Strouhal number, i.e., St p,cr Ϸ 0.008 for the present case, is identified: at St p ജ St p,cr the core jet converges to the axis of rotation while at St p ജ St p,cr it does not. The characteristics of the turbulent flow in the near and intermediate regions are quite different and depend upon the magnitude of St p . The near-field region, x / d ഛ 10-15, is dominated by a regime of global precession of the entire jet. As a result, the large-scale entrainment of the ambient fluid is substantially enhanced while the fine-scale turbulent mixing is suppressed. Under the supercritical regime (i.e., St p ജ St p,cr ), the jet in the far field resembles some features of the nonprecessing counterpart. Nevertheless, significant differences still retain in the statistical properties.

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“…The present study is performed using the mechanically rotating nozzle of Schneider et al, [26][27][28] shown schematically in Fig. 1.…”

Section: A Experimental Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Statistical analysis of the velocity field in a mechanical precessing jet flow

Nathan

2004

Physics of Fluids

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“…At sufficiently low St p , the trajectory of the jet is almost independent of the precession. However, above a critical value, the precession generates a helical flow in the near field associated with a low-pressure core (Schneider et al 1997a). Further increases in St p produce a gradual tightening of the helix (Mi & Nathan 2005), but provide no substantive changes to the qualitative features.…”

Section: Introductionmentioning

confidence: 98%

“…All of these issues complicate detailed investigation. To provide insight into this complex flow, a mechanically oscillating jet nozzle was developed in which a round jet is directed at an angle (typically 45 • ) to an axis about which it is rotated (Schneider et al 1997a). This allows independent variation of the controlling parameters.…”

Section: Introductionmentioning

confidence: 99%

The naturally oscillating flow emerging from a fluidic precessing jet nozzle

2008

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Phase-averaged and directionally triggered digital particle image velocimetry measurements were taken in longitudinal and transverse planes in the near field of the flow emerging from a fluidic precessing jet nozzle. Measurements were performed at nozzle inlet Reynolds and Strouhal numbers of 59 000 and 0.0017, respectively. Results indicate that the jet emerging from the nozzle departs with an azimuthal component in a direction opposite to that of the jet precession. In addition, the structure of the 'flow convergence' region, reported in an earlier study, is better resolved here. At least three unique vortex-pair regions containing smaller vortical 'blobs' are identified for the first time. These include a vortex-pair region originating from the foci on the downstream face of the nozzle centrebody, a vortex-pair region shed from the edge of the centrebody and a vortex-pair region originating from the downstream surface of the nozzle exit lip.

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