The influence of Reynolds number on a plane jet

Deo, Ravinesh C.; Mi, Jianchun; Nathan, Graham J.

doi:doi:10.1063/1.2959171

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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 ≤ Re_h ≤ 16 500, where Re_h ≡ U_bh/υ with U_b 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 Re_h = 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 Re_h despite all exit velocity profiles closely approximating a “top-hat” shape. The effect of Re_h on both the mean and turbulent fields is substantial for Re_h<10 000 but becomes weaker with increasing Re_h. The length of the jet’s potential core, initial primary-vortex shedding frequency, and far-field rates of decay and spread all depend on Re_h. The local Reynolds number, Re_y0.5 ≡ 2U_cy_0.5/υ, where U_c and y_0.5 are the local centerline velocity and half-width, respectively, are found to scale as Re_y0.5 ∼ x^1/2. It is also shown that, for Re_h ≥ 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.

Article Outline

INTRODUCTION
EXPERIMENT DETAILS
RESULTS AND DISCUSSION
1. Characterization of the exit conditions
2. The mean velocity field
3. The fluctuating velocity field
FURTHER DISCUSSION
1. Spectral results of different Reynolds numbers
2. Interpretation of differences in statistical properties due to varying Re_h
CONCLUSIONS

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KEYWORDS and PACS

Keywords

aircraft, jets, nozzles

PACS

47.60.Kz

Flows and jets through nozzles
47.85.Gj

Aerodynamics

ARTICLE DATA

Digital Object Identifier

http://dx.doi.org/10.1063/1.2959171

PUBLICATION DATA

ISSN

1070-6631 (print)

1089-7666 (online)

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$abstract.society.value is a Member of CrossRef

American Institute of Physics

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