In a turbulent jet, the numerical investigation of space-time correlations C(r, τ) at two-point and two-time of streamwise fluctuating velocities is presented along the nozzle lipline. Large-eddy simulation (LES) is performed for a Mach 0.9 turbulent jet issuing from a round nozzle. The turbulent boundary layer is well developed at the nozzle outlet, upon the inner wall, by adopting synthetic turbulent inlet boundary conditions. We study the cross correlations of streamwise fluctuating velocities at three particular streamwise positions, i.e., x = 0.71, 7.03, and 34.47r0, corresponding to different stages of jet development, where r0 is the radius of the nozzle. Present results show that the classical Taylor’s frozen-flow model is unable to predict C(r, τ) accurately in this strongly spatially developing shear flow since the distortion of the flow pattern is missing. The isocorrelation contours of C(r, τ) show a clearly elliptical feature, which is found to be well predicted by the elliptic approximation (EA) model [G.-W. He and J.-B. Zhang, “Elliptic model for space-time correlations in turbulent shear flows,” Phys. Rev. E 73, 055303 (2006)]. According to the EA model, C(r, τ) has a scaling form of C(rE, 0) with two characteristic velocities U and V, i.e., rE = (r − Uτ)2 + V2τ2. By examining LES data, it is found that the characteristic velocity U determined in LES is in general consistent with the theoretical Ut in the EA model, while the trend of V in LES also matches with that of the theoretical Vt. Additionally, it is interesting that the ratio of V to Vt is approximately a constant V/Vt ≃ 1.3 in the turbulent jet.
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Space-time correlations of velocity in a Mach 0.9 turbulent round jet
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November 2019
Research Article|
November 15 2019
Space-time correlations of velocity in a Mach 0.9 turbulent round jet
Peng-Jun-Yi Zhang
;
Peng-Jun-Yi Zhang
1
Department of Modern Mechanics, University of Science and Technology of China
, Hefei 230027, China
2
State Key Laboratory of Aerodynamics, China Aerodynamics Research and Development Center
, P.O. Box 211, Mianyang, Sichuan 621000, China
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Zhen-Hua Wan
;
Zhen-Hua Wan
a)
1
Department of Modern Mechanics, University of Science and Technology of China
, Hefei 230027, China
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De-Jun Sun
De-Jun Sun
1
Department of Modern Mechanics, University of Science and Technology of China
, Hefei 230027, China
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a)
Electronic mail: wanzh@ustc.edu.cn
Note: This paper is part of the Special Topic, Papers Selected from the 8th International Symposium on Physics of Fluids.
Physics of Fluids 31, 115108 (2019)
Article history
Received:
September 19 2019
Accepted:
November 01 2019
Citation
Peng-Jun-Yi Zhang, Zhen-Hua Wan, De-Jun Sun; Space-time correlations of velocity in a Mach 0.9 turbulent round jet. Physics of Fluids 1 November 2019; 31 (11): 115108. https://doi.org/10.1063/1.5128424
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