On Sound Generated by Instability Wave-Shock Cell Interaction in Supersonic Jets

Ray, Prasun K.; Cheung, Lawrence; Lele, Sanjiva K.

doi:10.2514/6.2004-2950

Cited by 1 publication

(2 citation statements)

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“…In our calculations, increasing the turbulence Reynolds number increases the peak instability wave amplitude and shifts the location of this peak downstream. 20 Our focus ͑for the most part͒ is not on absolute amplitudes, but rather relative trends in growth-which frequencies are more unstable? which azimuthal modes?-so the bulk of our conclusions is insensitive to the choice of turbulence Reynolds number ͑see the Appendix͒.…”

Section: Formulation and Methodologymentioning

confidence: 99%

“…The PSE code was validated based on comparisons to the linear PSE calculations of Malik and Chang 6 for a laminar M j = 2.5 jet. 20 A radially constant eddy viscosity is specified based on a constant local turbulence Reynolds number, Re t ϵ͑U cl ␦ I / t ͒ = 600. This value is roughly one order of magnitude larger than the peak eddy viscosity used in the RANS computations which is in basic agreement with the expectation that large-scale coherent disturbances exert a greater influence on mean-flow spreading than small-scale incoherent motions whose effect is modeled by the PSE eddy viscosity.…”

Section: Formulation and Methodologymentioning

confidence: 99%

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On the growth and propagation of linear instability waves in compressible turbulent jets

2009

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The linear instability of compressible axisymmetric unheated jets is investigated numerically. Solutions to the linear parabolized stability equations with Reynolds-averaged Navier-Stokes mean flows are used to describe the streamwise evolution of instability waves. For transonic jets, helical ͑azimuthal mode number m =1͒ instability waves tend to exhibit the largest gain over the jet potential core followed by the m = 2 and axisymmetric modes. At higher frequencies, the disparity in energy growth between the different azimuthal modes decreases, and there is a progressive reduction in energy growth as azimuthal mode number is increased from two to four. The entropic and pressure components of the total energy are compared to the kinetic energy. We find that the pressure term tends to be small, while the importance of the entropic component increases with frequency and decreases with azimuthal mode number. It is shown that the helical mode growth rates exhibit similarity when a local "mixing layer" scaling is adopted. This similarity is then used to concisely illustrate the stabilizing effect of compressibility over a broad range of frequencies and Mach numbers. Computed phase velocities are compared to measured convective velocities for unforced turbulent jets with Mach numbers M j = 0.51 and M j = 1.41. Good agreement is observed provided that the appropriate azimuthal mode number is selected.

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Section: Formulation and Methodologymentioning

confidence: 99%

Section: Formulation and Methodologymentioning

confidence: 99%