Low-dimensional model of a supersonic rectangular jet

Moreno, D.; Krothapalli, A.; Alkislar, Mehmet; Lourenco, L.

doi:10.1103/physreve.69.026304

Cited by 40 publications

(20 citation statements)

References 23 publications

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“…The technique has been successfully applied to a variety of practical flow problems, including boundary layers, 26 turbulent jets, 27 as well as compressible flows. 28 PIV data are particularly suited for POD analyses since the entire spatial velocity field is available, leading to the construction of global eigenmodes.…”

Section: Introductionmentioning

confidence: 99%

Unsteady flow organization of compressible planar base flows

2007

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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.

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Section: Introductionmentioning

confidence: 99%

Unsteady flow organization of compressible planar base flows

2007

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“…It has been applied to a variety of fluid dynamic problems of practical interest, including boundary layers (Aubry et al 1988) and compressible flows (Moreno et al 2004), to produce low-dimensional representations of the flow phenomena present. Particle image velocimetry (PIV) data are particularly suited for the POD analyses, since the entire spatial velocity field is available by snapshots, leading to the construction of global eigenmodes that can be used to further characterize the instantaneous spatial organization of the flow.…”

Section: Introductionmentioning

confidence: 99%

Unsteady aspects of an incident shock wave/turbulent boundary layer interaction

2009

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An incident shock wave/turbulent boundary layer interaction at Mach 2.1 is investigated using particle image velocimetry in combination with data processing using the proper orthogonal decomposition, to obtain an instantaneous and statistical description of the unsteady flow organization. The global structure of the interaction is observed to vary considerably in time. Although reversed flow is often measured instantaneously, on average no reversed flow is observed. On an instantaneous basis, the interaction exhibits a multi-layered structure, characterized by a relatively highvelocity outer region and low-velocity inner region. Discrete vortical structures are prevalent along their interface, which create an intermittent fluid exchange as they propagate downstream. A statistical analysis suggests that the instantaneous fullness of the incoming boundary layer velocity profile is (weakly) correlated with the size of the separation bubble and position of the reflected shock wave. The eigenmodes show an energetic association between velocity fluctuations within the incoming boundary layer, separated flow region and across the reflected shock wave, and portray subspace features that represent the phenomenology observed within the instantaneous realizations.

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“…An energy-based inner product is preferred because it retains the stable equilibrium points at the origin in the low-dimensional model [9] . Applying this method to flows at moderately high Mach numbers has generated satisfactory results [7] . Eqs.…”

Section: The Pod Vector and Inner Productmentioning

confidence: 92%

“…Thus, the inner product could lose its direct physical interpretation, since velocity and temperature cannot be simply added together. Even if we do not try to make physical sense of the inner product, there remains the question of how to combine kinetic and thermodynamic variables such that the main features of the flow are captured efficiently [7] . Lumley et al [8] introduced a form of inner product, which added normalized velocity and density fluctuations in an optimal way (hereafter referred to as a normalized inner product).…”

Section: Introductionmentioning

confidence: 99%

Analysis of flow structures in supersonic plane mixing layers using the POD method

Yang

2008

Sci. China Ser. G-Phys. Mech. As

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The proper orthogonal decomposition (POD) method was applied to analyzing the database obtained from the direct numerical simulation (DNS) of supersonic plane mixing layers. The effect of different forms of the inner products in the POD method was investigated. It was observed that the mean flow contributes to a predominant part of the total flow energy, and the energy spectrum of the turbulence fluctuations covers a wide range of POD modes. The patterns of leading (high energy) POD modes reveal that the flow structures exhibit spanwise counter rotating rolls, as well as oblique vortices. These flow patterns are insensitive to the velocity of the observer. As the convective Mach number increases, the energy spectrum becomes wider, the leading POD modes contain more complicated structures, and the flow becomes more chaotic. coherent structure, compressible mixing layer, POD, low-dimensional model

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Low-dimensional model of a supersonic rectangular jet

Cited by 40 publications

References 23 publications

Unsteady flow organization of compressible planar base flows

Unsteady flow organization of compressible planar base flows

Unsteady aspects of an incident shock wave/turbulent boundary layer interaction

Analysis of flow structures in supersonic plane mixing layers using the POD method

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