Two-point laser Doppler velocimetry measurements in a Mach 1.2 cold supersonic jet for statistical aeroacoustic source model

Kerhervé, Franck; Jordan, Peter; Gervais, Yves; Valière, Jean-Christophe; Braud, P.

doi:10.1007/s00348-004-0815-1

Cited by 72 publications

(39 citation statements)

References 28 publications

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“…Subsequently, a methodology dedicated to the measurement of such a quantity is used. This method is derived from the classical integral length scale estimation based on twopoint measurements [22]. An evaluation of the longitudinal (i.e.…”

Section: Integral Length Scalementioning

confidence: 99%

On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator

Bénard

Moreau

2011

Flow Turbulence Combust

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Commercial and military aircrafts or miniature aerial vehicles can suffer from massive flow separation when high angles of attack are required. Single dielectric barrier discharge (DBD) actuators have demonstrated their capability of controlling such a separated flow at low external velocity. However, the processes resulting in the improvement of the flight performances remain unclear. In the present study, the reattachment process along the suction side of a NACA 0015 placed at an angle of attack of 16 • is experimentally investigated for an external velocity of 20 m/s (Re = 260,000). A single DBD actuator is mounted at the leading edge of the model. The velocity fields above the suction side of the airfoil are measured by a high-speed acquisition system (3 kHz). The results indicate that the baseline flow presents shed vortices that form at the leading edge and linearly grow along the free shear layer axis. This vortex shedding is organized and exhibits a specific frequency of about 90 Hz. The continuous actuation produces a partial flow reattachment up to 70% of the chord length. Temporal cross-correlation function indicates the presence of a vortex shedding at the trailing edge of the controlled flow. Finally, the temporal analysis demonstrates that the reattachment process requires 50 ms to reach a stabilized attached flow. The time-resolved analysis of the reattachment suggests that the actuation by plasma discharge acts as a catalyser by reinforcing one of the coherent flow structures already existing in the natural flow.

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Section: Integral Length Scalementioning

confidence: 99%

On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator

Bénard

Moreau

2011

Flow Turbulence Combust

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“…Attention was turned to use of non-intrusive laser-based methods when these became available. Laser Doppler Anemometry (LDA) -as for HWA probes applied in traversed multi-point mode -was successfully used by Lau et al (1979) and Lau (1980) for 2 nd -order correlations, and by Kerherve et al (2004) to study the longitudinal component of both 2 nd -and 4 th -order correlations, for axial separation only, in a high speed shear layer, enabling analytical expressions to be derived for the spatial and temporal parts of the correlation function. However, the point-based nature of LDA still seriously constrains its use in extraction of whole-field spatio-temporal correlation maps, in principle needed for all three velocity components and for all components of the separation vector.…”

Section: Introductionmentioning

confidence: 99%

Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

Pokora

McGuirk

2015

J. Fluid Mech.

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Stereoscopic three-component particle image velocimetry (3C-PIV) measurements have been made in a turbulent round jet to investigate the spatio-temporal correlations that are the origin of aerodynamic noise. Restricting attention to subsonic, isothermal jets, measurements were taken in a water flow experiment where, for the same Reynolds number and nozzle size, the shortest time scale of the dynamically important turbulent structures is more than an order of magnitude greater that in equivalent airflow experiments, greatly facilitating time-resolved PIV measurements. Results obtained (for a jet nozzle diameter and velocity of 40 mm and $1~\text{m}~\text{s}^{-1}$, giving $\mathit{Re}=4\times 10^{4}$) show that, on the basis of both single-point statistics and two-point quantities (correlation functions, integral length scales) the present incompressible flow data are in excellent agreement with published compressible, subsonic airflow measurements. The 3C-PIV data are first compared to higher-spatial-resolution 2C-PIV data and observed to be in good agreement, although some deterioration in quality for higher-order correlations caused by high-frequency noise in the 3C-PIV data is noted. A filter method to correct for this is proposed, based on proper orthogonal decomposition (POD) of the 3C-PIV data. The corrected data are then used to construct correlation maps at the second- and fourth-order level for all velocity components. The present data are in accordance with existing hot-wire measurements, but provide significantly more detailed information on correlation components than has previously been available. The measured relative magnitudes of various components of the two-point fourth-order turbulence correlation coefficient ($R_{ij,kl}$) – the fundamental building block for free shear flow aerodynamic noise sources – are presented and represent a valuable source of validation data for acoustic source modelling. The relationship between fourth-order and second-order velocity correlations is also examined, based on an assumption of a quasi-Gaussian nearly normal p.d.f. for the velocity fluctuations. The present results indicate that this approximation shows reasonable agreement for the measured relative magnitudes of several correlation components; however, areas of discrepancy are identified, indicating the need for work on alternative models such as the shell turbulence concept of Afsar (Eur. J. Mech. (B/Fluids), vol. 31, 2012, pp. 129–139).

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“…One exception is Zaman [12], that documented the impact of lobed mixers on centerline statistics of the jet. Another exception is Kerherve et al [13] that measured a supersonic jet in a forward flight environment. That work contains plots of radial turbulence intensity profiles at various axial stations in a shock-containing jet.…”

Section: Introductionmentioning

confidence: 99%

Establishing Consensus Turbulence Statistics for Hot Subsonic Jets

Bridges

Werner

2010

16th AIAA/CEAS Aeroacoustics Conference

108

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Many tasks in fluids engineering require knowledge of the turbulence in jets. There is a strong, although fragmented, literature base for low order statistics, such as jet spread and other meanvelocity field characteristics. Some sources, particularly for low speed cold jets, also provide turbulence intensities that are required for validating Reynolds-averaged Navier-Stokes (RANS) Computational Fluid Dynamics (CFD) codes. There are far fewer sources for jet spectra and for space-time correlations of turbulent velocity required for aeroacoustics applications, although there have been many singular publications with various unique statistics, such as Proper Orthogonal Decomposition, designed to uncover an underlying low-order dynamical description of turbulent jet flow. As the complexity of the statistic increases, the number of flows for which the data has been categorized and assembled decreases, making it difficult to systematically validate prediction codes that require high-level statistics over a broad range of jet flow conditions. For several years, researchers at NASA have worked on developing and validating jet noise prediction codes. One such class of codes, loosely called CFD-based or statistical methods, uses RANS CFD to predict jet mean and turbulent intensities in velocity and temperature. These flow quantities serve as the input to the acoustic source models and flow-sound interaction calculations that yield predictions of far-field jet noise. To develop this capability, a catalog of turbulent jet flows has been created with statistics ranging from mean velocity to space-time correlations of Reynolds stresses. The present document aims to document this catalog and to assess the accuracies of the data, e.g. establish uncertainties for the data. This paper covers the following five tasks:• Document acquisition and processing procedures used to create the particle image velocimetry (PIV) datasets.• Compare PIV data with hotwire and laser Doppler velocimetry (LDV) data published in the open literature.• Compare different datasets acquired at roughly the same flow conditions to establish uncertainties.• Create a 'consensus' dataset for a range of hot jet flows, including uncertainty bands.• Analyze this consensus dataset for self-consistency and compare jet characteristics to those of the open literature.One final objective fulfilled by this work was the demonstration of a universal scaling for the jet flow fields, at least within the region of interest to aeroacoustics. The potential core length and the spread rate of the half-velocity radius were used to collapse of the mean and turbulent velocity fields over the first 20 jet diameters in a highly satisfying manner. Nomenclature ! "shear layer thickness, U j /|dU/dr| max # shear layer coordinate, = (r -r 0.5 )/! " , # $ shear layer growth rate coordinate, = (r -r 0·5

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Two-point laser Doppler velocimetry measurements in a Mach 1.2 cold supersonic jet for statistical aeroacoustic source model

Cited by 72 publications

References 28 publications

On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator

On the Vortex Dynamic of Airflow Reattachment Forced by a Single Non-thermal Plasma Discharge Actuator

Stereo-PIV measurements of spatio-temporal turbulence correlations in an axisymmetric jet

Establishing Consensus Turbulence Statistics for Hot Subsonic Jets

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