Quadrant Analysis in Turbulence Research: History and Evolution

Wallace, J. M.

doi:10.1146/annurev-fluid-122414-034550

Cited by 293 publications

(186 citation statements)

References 145 publications

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“…We found that 53% of the negative RSS comes from ejection events, while 47% of the negative RSS from sweep events, which respectively accounts for 40% and 35% of the total RSS. These results are consistent with the measurements by Nagano & Tagawa (1998) in a turbulent pipe flow, also reported in Wallace (2016). As observed in several analyses from literature (Lozano-Durán et al 2012, Lozano-Durán & Jiménez 2014, Robinson 1991, the individual contributions of each of the quadrant events to the total RSS strongly depends on the wall-normal location.…”

Section: Intense Rss Eventssupporting

confidence: 92%

Spatial–spectral characteristics of momentum transport in a turbulent boundary layer

2017

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Spectral content and spatial organization of momentum transport events are investigated in a turbulent boundary layer at the Reynolds number (Re τ ) = 2700, with time-resolved planar particle image velocimetry. The spectral content of the Reynolds-shear-stress fluctuations reveals that the largest range of time and length scales can be observed in proximity to the wall, while this range becomes progressively more narrow when the wall distance increases. Farther from the wall, longer time and larger length scales exhibit an increasing spectral content. Wave velocities of transport events are estimated from wavenumber-frequency power spectra at different wall-normal locations. Wave velocities associated with ejection events (Q2) are lower than the local average streamwise velocity, while sweep events (Q4) are characterized by wave velocities larger than the local average velocity. These velocity deficits are almost insensitive to the wall distance, which is also confirmed from time tracking the intense transport events. The vertical advection velocities of the intense ejection and sweep events are on average a small fraction of the friction velocity U τ , different from previous observations in a channel flow. In the range of wall-normal locations 60 < y + < 600, sweeps are considerably larger than ejections, which could be because the ejections are preferentially located in between the legs of hairpin packets. Finally, it is observed that negative quadrant events of the same type tend to appear in groups over a large spatial streamwise extent.

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Section: Intense Rss Eventssupporting

confidence: 92%

Spatial–spectral characteristics of momentum transport in a turbulent boundary layer

2017

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“…For a comprehensive overview on quadrant analysis see Ref. [18]. The turbulent heat flux can be decomposed into four different terms or quadrants, which can be summarized as (1)…”

Section: F Contributions Of Turbulent Heat Flux Quadrants To the Nusmentioning

confidence: 99%

Characteristics of turbulent heat transfer in an annulus at supercritical pressure

et al. 2017

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Heat transfer to fluids at supercritical pressure is different from heat transfer at lower pressures due to strong variations of the thermophysical properties with the temperature. We present and analyze results of direct numerical simulations of heat transfer to turbulent CO 2 at 8 MPa in an annulus. Periodic streamwise conditions are imposed so that mean streamwise acceleration due to variations in the density does not occur. The inner wall of the annulus is kept at a temperature of 323 K, while the outer wall is kept at a temperature of 303 K. The pseudocritical temperature T pc = 307.7 K, which is the temperature where the thermophysical properties vary the most, can be found close to the inner wall. This work is a continuation of an earlier study, in which turbulence attenuation due to the variable thermophysical properties of a fluid at supercritical pressure was studied. In the current work, the direct effects of variations in the specific heat capacity, thermal diffusivity, density, and the molecular Prandtl number on heat transfer are investigated using different techniques. Variations in the specific heat capacity cause significant differences between the mean nondimensionalized temperature and enthalpy profiles. Compared to the enthalpy fluctuations, temperature fluctuations are enhanced in regions with low specific heat capacity and diminished in regions with a large specific heat capacity. The thermal diffusivity causes local changes to the mean enthalpy gradient, which in turn affects molecular conduction of thermal energy. The turbulent heat flux is directly affected by the density, but it is also affected by the mean molecular Prandtl number and attenuated or enhanced turbulent motions. In general, enthalpy fluctuations are enhanced in regions with a large mean molecular Prandtl number, which enhances the turbulent heat flux. While analyzing the Nusselt numbers under different conditions it is found that heat transfer deterioration or enhancement can occur without streamwise acceleration or mixed convection conditions. Finally, through a combination of a relation between the Nusselt number and the radial heat fluxes, a quadrant analysis of the turbulent heat flux, and conditional averaging of the heat flux quadrants, it is shown that heat transfer from a heated surface depends on the density and the molecular Prandtl number of both hot fluid moving away from a heated surface as well as the thermophysical properties of relatively cold fluid moving towards it.

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“…From the discussion of figure 14, it is evident that such an event leads to negative amplification of the local acoustic mode, which should appear as a negative fluctuation in −∂ψ A /∂x. The quadrant analysis described in Wallace (2016) is used to establish this connection, using ω θ and −∂ψ A /∂x, and the results are provided in figure 16. The joint probability distribution function (JPDF) of these two signals, using the time history at a typical location in the core ((x, r) = (5.5, 0.25)), is shown in (a).…”

Section: Core Dynamics Of the Acoustic Modementioning

confidence: 99%

Acoustic, hydrodynamic and thermal modes in a supersonic cold jet

Nair

Gaitonde

2016

J. Fluid Mech.

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Large-eddy simulation data for a Mach 1.3 round jet are decomposed into acoustic, hydrodynamic and thermal components using Doak's momentum potential theory. The decomposed fields are then analysed to examine the properties of each mode and their dynamics based on the transport equation for the total fluctuating enthalpy. The solenoidal fluctuations highlight hydrodynamic components of the jet and capture the shear layer growth and breakdown process. The acoustic mode exhibits a jittering coherent wavepacket structure in the turbulent region and consequent highly directional downstream radiation. The expected radial decay rates, r for acoustic, are recovered and closely follow the universal radiation spectra in the sideline and downstream directions. The scalogram of the acoustic mode in the near-acoustic-field region is consistent with that of the pressure perturbation signal in the acoustic-frequency range, but effectively removes the hydrodynamic and thermal content. The time-resolved and mean behaviour of terms in the total fluctuating enthalpy equation is analysed in detail. A large-scale intermittent event in the near-acoustic field is shown to be associated with an intrusion of vortices from the shear layer into the core of the jet. Acoustic sources are created when the resulting negative fluctuations in the solenoidal component interact with positive fluctuations in the Coriolis acceleration term. The latter are associated with regions of high vorticity on the inner side of the shear layer. In contrast, sinks result from the interaction of solenoidal momentum fluctuations with positive entropy gradients along entrainment streaks.

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Quadrant Analysis in Turbulence Research: History and Evolution

Cited by 293 publications

References 145 publications

Spatial–spectral characteristics of momentum transport in a turbulent boundary layer

Spatial–spectral characteristics of momentum transport in a turbulent boundary layer

Characteristics of turbulent heat transfer in an annulus at supercritical pressure

Acoustic, hydrodynamic and thermal modes in a supersonic cold jet

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