Spatial waves in turbulent jets

Abstract

Measurements of the spatial development of disturbance pressure waves in a low-speed axisymmetric turbulent free jet have been carried out. The results show that the wavenumbers of the pressure waves increase monotonically, while the phase velocities decrease as the Strouhal number of the jet increases. The pressure disturbance grows to a maximum at some distance downstream from the nozzle and then decays. The distributions of the amplitude of the pressure waves along the jet are similar if the data are plotted against a normalized distance St x/D. The most amplified mode is at a Strouhal number of 0.5 for the shear layer and 0.35 for the center line. The wave characteristics follow closely the linear stability theory of an inviscid diverged shear flow.

Development of turbulence in subsonic submerged jets

“…A small acoustic disturbance at some frequency f a within this range near the nozzle transforms into a growing hydrodynamic wave. There is evidence for this in the experimental results of Crow and Champagne [98] and Chan [99]. It follows from the experimental data in Fig.…”

“…We see that ǫ u is maximal for St a ≈ 0.3. Figure 9 a taken from [99] shows that the gain factor depends nonmonotonically on distance from the nozzle exit: it has a maximum at x/D = (0.75÷1.25)/St a . A theoretical dependence similar to that shown in Fig.…”

Wave Packets and Turbulent Jet Noise

“…For typical velocity profiles of a subsonic unheated round jet, at most one family of unstable modes exists for each azimuthal mode number (Mattingly & Chang 1974). Heuristic energy-integral formulations (Chan 1974, Liu 1974, Mankbadi & Liu 1981 or a rigorous multiple-scales analysis (Crighton & Gaster 1976, Tam & Morris 1980) extends the parallel flow theory to weakly diverging jet mean flow. A computationally simpler approach that delivers quantitatively similar results (Chang et al 1993) is the parabolized stability equation (PSE) framework (summarized in Herbert 1997).…”

Large-Eddy Simulations of Forced Three-Dimensional Impinging Jets

“…The importance of coherent structures in the transport of momentum and in noise production has been clearly demonstrated in a variety of flow fields (c.g., Ho and Nosseir, 1981;Nosseir and Ho, 1982;Moore, 1977) and has motivated many numerical studies aimed at understanding the dynamics of these structures (e.g., Davis and Moore, 1982;Metcalfe et al, 1987). In free jet flows, the of coherent structures has been studied by artificially exciting the jet at a specified frequency (e.g., Crow and Champagne, 1971;Chan, 1974Chan, , 1977Zaman and Hussain, 1980). This approach suppresses the natural instability of the jet and, thus, allows detailed study of the characteristics of the artificially created coherent structures.…”