The Preferred-Mode Coherent Structure in the Near Field of an Axisymmetric Jet With and Without Excitation
The ‘preferred-mode’ coherent structure in the near field of an axisymmetric jet is educed for different Reynolds numbers and for the two limiting asymptotic states of the exit boundary layer: laminar and fully- developed turbulent. Distributions of phase-average longitudinal and lateral velocities, coherent vorticity, coherent and incoherent turbulence Reynolds stresses, and coherent strain rate and production are obtained via phase-locked hot-wire measurements over the spatial extent of the coherent structure, for controlled excitation at the jet Strouhal number of 0.3. These properties are found to be independent of the initial condition but show weak dependence on the Reynolds number up to about 105. The naturally-occurring coherent structure in the unexcited jet, educed via an optimized conditional sampling scheme, shows no clear dependence on the jet Reynolds number up to 8 × 105.
KeywordsReynolds Number Shear Layer Reynolds Stress Coherent Structure Conditional Sampling
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- 2.Hussain, A. K. M. F. & Zaman, K. B. M. Q., 1981 J. Fluid Mech. (to appear).Google Scholar
- 3.Zaman, K.B.M.Q. & Hussain, A.K.M.F., J. Fluid Mech. 101, 449–491.Google Scholar
- 4.Husain, Z. D. & Hussain, A. K. M. F., A.I.A.A. J. 17, 48–55.Google Scholar
- 7.Zaman, K. B. M. Q. & Hussain, A. K. M. F., 1981 (submitted to J. Fluid Mech.).Google Scholar
- 9.Lau, J. C., 1979 Proc. Roy. Soc. A 3S8, 547–571.Google Scholar
- 11.Crighton, D. G., 1980 Lecture Notes in Physics, 136, 341–362.Google Scholar
- 12.Hasan, M. A. Z. & Hussain, A. K. M. F., 1981 J. Fluid Mech. (to appear).Google Scholar
- 13.Laufer, J., 1974 in Omaggio A. Carlo Ferrari, 451–464.Google Scholar