Characterization of Unsteady Flow Structures Near Leading-Edge Slat: Part I: PIV Measurements

Jenkins, Luther N.; Khorrami, Mehdi R.; Choudhari, Meelan M.

doi:10.2514/6.2004-2801

Cited by 85 publications

(89 citation statements)

References 11 publications

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“…Similar to the 2D computations in [19], the present simulations are based on the 30P30N model geometry that was used during the experiments in the Basic Aerodynamic Research Tunnel (BART) at NASA Langley Research Center [22]. The relatively small (28 inch by 40 inch) test section of BART precludes meaningful noise measurements in this facility; however, it is well suited for characterizing the fluid dynamics of the high-lift configuration.…”

Section: A Geometry Of High-lift Configuration and Flow Conditionsmentioning

confidence: 99%

“…Towards that goal, a joint study involving particle image velocimetry (PIV) measurements and 2D unsteady computations for a generic, unswept three-element high-lift configuration was described in Refs. [22] and [19], respectively. The objective behind that work was to shed additional light on the unresolved questions pertaining to the development of unsteady flow structures within the slat cove region (including the recirculation zone of the cove) and the interaction between these structures and the adjacent solid surfaces.…”

Section: Introductionmentioning

confidence: 99%

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Slat Cove Unsteadiness: Effect of 3D Flow Structures

Choudhari

Khorrami

2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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Our previous studies have indicated that 2D, time accurate computations based on a pseudo-laminar zonal model of the slat cove region (within the framework of the Reynolds-Averaged Navier-Stokes equations) are inadequate for predicting the full unsteady dynamics of the slat cove flow field. Even though such computations could capture the large-scale, unsteady vorticity structures in the slat cove region without requiring any external forcing, the simulated vortices were excessively strong and the recirculation zone was unduly energetic in comparison with the PIV measurements for a generic high-lift configuration. To resolve this discrepancy and to help enable physics based predictions of slat aeroacoustics, the present paper is focused on 3D simulations of the slat cove flow over a computational domain of limited spanwise extent. Maintaining the pseudo-laminar approach, current results indicate that accounting for the threedimensionality of flow fluctuations leads to considerable improvement in the accuracy of the unsteady, nearfield solution. Analysis of simulation data points to the likely significance of turbulent fluctuations near the reattachment region toward the generation of broadband slat noise. The computed acoustic characteristics (in terms of the frequency spectrum and spatial distribution) within short distances from the slat resemble the previously reported, subscale measurements of slat noise.

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Section: A Geometry Of High-lift Configuration and Flow Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Slat Cove Unsteadiness: Effect of 3D Flow Structures

Choudhari

Khorrami

2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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“…On the other hand, it is shown that the resolved kinetic energy levels are higher further into the recirculation bubble for the finer temporal resolution, which is expected, since more energy-bearing eddies characterized by short time scales may be resolved. For a similar high-lift configuration, experimental and numerical studies were carried out by Jenkins et al [4], Choudhari and Khorrami [1] and Lockard and Choudhari [6]. In comparison with those results, the resolved energy intensity in the free shear-layer is much smaller here, but the overall tendency is comparable.…”

Section: Resolved Instantaneous Flow and Mean Flowmentioning

confidence: 76%

Hybrid RANS-LES Simulation of Turbulent High-Lift Flow in Relation to Noise Generation

Nebenführ

Peng

Davidson

2012

Progress in Hybrid RANS-LES Modelling

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Turbulence-resolving simulations have been performed using hybrid RANS-LES approaches for the turbulent flow around a three-element high-lift configuration. The main purpose is to explore the effect of some modeling-related numerical aspects on the simulation of resolved velocity and pressure fluctuations as potent noise-generating sources. Along with a presentation of resolved instantaneous and mean flow features, the impact of the time step and the spanwise extent of the computational domain is investigated. It is shown that the temporal resolution and the spanwise extension of the computational domain impose effects not only on the prediction of mean flow, but more significantly on the correlation of resolved turbulent structures, which may consequently affect the accuracy of flow-generated noise properties.

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“…[13][14][15] The two-dimensional (2-D) computations of this type helped clarify the cause-effect relationships between the near-field flow structures and the far-field noise; however, a further assessment of these computations 16 indicated excessively energetic vortical structures in comparison with the PIV measurements. 17 Three-dimensional (3-D) computations over a narrow portion of the model span 18 led to significant improvement in that regard, yielding a favorable comparison with the PIV measurements. 17 The importance of 3-D fluctuations in determining the unsteady dynamics within the cove region has also been confirmed via computations for other high-lift configurations and using alternative numerical algorithms.…”

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confidence: 99%

“…17 Three-dimensional (3-D) computations over a narrow portion of the model span 18 led to significant improvement in that regard, yielding a favorable comparison with the PIV measurements. 17 The importance of 3-D fluctuations in determining the unsteady dynamics within the cove region has also been confirmed via computations for other high-lift configurations and using alternative numerical algorithms. 19,20 The acoustic sources in the slat cove have been investigated experimentally 17 using the 30P/30N model.…”

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confidence: 99%

The Variation of Slat Noise with Mach and Reynolds Numbers

Lockard

Choudhari

2011

17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference)

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The slat noise from the 30P30N high-lift system has been computed using a computational fluid dynamics code in conjunction with a Ffowcs Williams-Hawkings solver. By varying the Mach number from 0.13 to 0.25, the noise was found to vary roughly with the 5th power of the speed. Slight changes in the behavior with directivity angle could easily account for the different speed dependencies reported in the literature. Varying the Reynolds number from 1.4 to 2.4 million resulted in almost no differences, and primarily served to demonstrate the repeatability of the results. However, changing the underlying hybrid Reynolds-averaged-Navier-Stokes/Large-Eddy-Simulation turbulence model significantly altered the mean flow because of changes in the flap separation. However, the general trends observed in both the acoustics and near-field fluctuations were similar for both models.

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Characterization of Unsteady Flow Structures Near Leading-Edge Slat: Part I: PIV Measurements

Cited by 85 publications

References 11 publications

Slat Cove Unsteadiness: Effect of 3D Flow Structures

Slat Cove Unsteadiness: Effect of 3D Flow Structures

Hybrid RANS-LES Simulation of Turbulent High-Lift Flow in Relation to Noise Generation

The Variation of Slat Noise with Mach and Reynolds Numbers

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