Large-scale structure and entrainment in the supersonic mixing layer

Clemens, Noel T.; Mungal, M. G.

doi:10.1017/s0022112095000310

Cited by 332 publications

(152 citation statements)

References 25 publications

Supporting

Mentioning

128

Contrasting

Order By: Relevance

“…They found that the spatial fluctuations were indeed larger in the streamwise direction than in the vertical direction, suggesting that the overall global dynamics were dominated by a pulsating motion. Interestingly, there is evidence suggested by Clemens and Mungal 41 that the organization of the large-scale turbulent structures develop a more streamwise orientation with increasing compressibility.…”

Section: -6mentioning

confidence: 96%

Unsteady flow organization of compressible planar base flows

2007

View full text Add to dashboard Cite

The unsteady flow features of a series of two-dimensional, planar base flows are examined, within a range of low-supersonic Mach numbers in order to gain a better understanding of the effects of compressibility on the organized global dynamics. Particle image velocimetry is used as the primary diagnostic tool in order to characterize the instantaneous near wake behavior, in combination with data processing using proper orthogonal decomposition. The results show that the mean flowfields are simplified representations of the instantaneous flow organizations. Generally, each test case can be characterized by a predominant global mode, which undergoes an evolution with compressibility, within the Mach number range considered. ͑The term "global mode" is defined herein as an organized global dynamical behavior of the near wake region, recognizing that the near wake dynamics may be describable in terms of several global modes.͒ At Mach 1.46, the predominant global mode can be characterized by a sinuous or flapping motion. With increasing compressibility, this flapping mode decreases, and the predominant global mode evolves into a pulsating motion aligned with the wake axis at Mach 2.27. These global modes play an important role in the distributed nature of the turbulence properties. The turbulent mixing processes become increasingly confined to a narrower redeveloping wake with increasing compressibility. Global maximum levels of the streamwise turbulence intensity and the kinematic Reynolds shear stress occur within the vicinity of the mean reattachment location, and show no systematic trend with compressibility. In contrast, the global maximum level of the vertical turbulence intensity moves upstream from the redeveloping wake toward the mean reattachment location. The vertical turbulence intensity decays thereafter more slowly than the other turbulence quantities. Overall, the local maximum levels of the turbulence properties decrease appreciably with increasing compressibility.

show abstract

Section: -6mentioning

confidence: 96%

Unsteady flow organization of compressible planar base flows

2007

View full text Add to dashboard Cite

show abstract

“…Moreover, experiments indicate that in the moderately to fully compressible regime with M = O(1) (including low supersonic speeds M > 1), mixing layers continue to behave in more-or-less the same manner as in the incompressible regime (Clemens & Mungal 1995, Elliott, Samimy & Arnette 1995. In particular, vortex roll-up remains the most significant feature of mixing layer development (Urban & Mungal 2001, Olsen & Dutton 2003.…”

mentioning

confidence: 98%

Nonlinear development of subsonic modes on compressible mixing layers: a unified strongly nonlinear critical-layer theory

Sparks

2008

J. Fluid Mech.

View full text Add to dashboard Cite

This paper is concerned with the nonlinear instability of compressible mixing layers in the regime of small to moderate values of Mach number M , in which subsonic modes play a dominant role. At high Reynolds numbers of practical interest, previous studies have shown that the dominant nonlinear effect controlling the evolution of an instability wave comes from the so-called critical layer. In the incompressible limit (M = 0), the critical-layer dynamics are strongly nonlinear, with nonlinearity being associated with the logarithmic singularity of the velocity fluctuation (Goldstein & Leib 1988). In contrast, in the fully compressible regime (M = O(1)), nonlinearity is associated with a simple-pole singularity in the temperature fluctuation, and enters in a weakly nonlinear fashion (Goldstein & Leib 1989). In this paper, we first consider a weakly compressible regime, corresponding to the distinguished scaling M = O(ǫ 1/4 ), for which the strongly nonlinear structure persists but is affected by compressibility at leading order (where ǫ ≪ 1 measures the magnitude of the instability mode). A strongly nonlinear system governing the development of the vorticity and temperature perturbation is derived. It is further noted that the strength of the pole singularity is controlled by T ′ c , the mean temperature gradient at the critical level, and for typical base-flow profiles T ′ c is small even when M = O(1). By treating T ′ c as an independent parameter of O(ǫ 1/2 ), we construct a composite strongly nonlinear theory, from which the weakly nonlinear result for M = O(1) can be derived as an appropriate limiting case. Thus the strongly nonlinear formulation is uniformly valid for O(1) Mach numbers. Numerical solutions show that this theory captures vortex roll-up process, which remains the most prominent feature of compressible mixing-layer transition. The theory offers an effective tool for investigating the nonlinear instability of mixing layers at high Reynolds numbers.

show abstract

“…This seeding method is similar in concept to past studies using ethanol condensation (Bourdon and Dutton, 1999, Clemens and Mungal, 1995, Mahadevan et al, 1992, Smith and Dutton, 2001). Acetone vapor is added to the air upstream of the jet nozzle, and condenses when the flow is expanded to sufficiently high velocity.…”

Section: Experimental Facilities and Methodsmentioning

confidence: 81%

A Study of Convective Velocity in Supersonic Jets Using MHz Rate Imaging

Blohm

Lempert

Samimy

et al. 2006

44th AIAA Aerospace Sciences Meeting and Exhibit

View full text Add to dashboard Cite

MHz-rate flow visualization and Planar Doppler Velocimetry (PDV) measurements were carried out in Mach 1.3 and 2.0 axisymmetric jets with Reynolds number based on the nozzle exit diameter of over 10 6 using a burst mode laser and a pair of high-speed CCD framing cameras. Determination of convective velocity from flow visualization using planar space-time correlation reveals strong evidence of bias due to distinct artificial seeding gradients resulting from partial seeding of the flow (i.e. seeding of the mixing region, but not the jet core and the ambient). This bias can be somewhat rectified if the measurements are restricted to the early part of the shear layer growth, where the structures are relatively coherent and the correlation level is high and contains a distinct peak. The bias can be nearly eliminated if the entire flow field is seeded and PDV, rather than flow visualization, is used to determine the convective velocity. Under these circumstances, the measured convective velocity agrees very well with theoretical predictions.

show abstract

Large-scale structure and entrainment in the supersonic mixing layer

Cited by 332 publications

References 25 publications

Unsteady flow organization of compressible planar base flows

Unsteady flow organization of compressible planar base flows

Nonlinear development of subsonic modes on compressible mixing layers: a unified strongly nonlinear critical-layer theory

A Study of Convective Velocity in Supersonic Jets Using MHz Rate Imaging

Contact Info

Product

Resources

About