Exploring Noise Sources Using Simultaneous Acoustic Measurements and Real-Time Flow Visualizations in Jets

Hileman, James; Thurow, Brian S.; Samimy, Mo

doi:10.2514/2.1599

Cited by 30 publications

(24 citation statements)

References 25 publications

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“…The periods of relative quiet also had a series of robust structures, but it did not have entrainment of the ambient air into the centerline. This observation is in agreement with the subjective interpretations of the simultaneous data presented in Hileman and Samimy [2001] and Hileman et al [2002]. Another interesting difference between the two states (NG versus RQ) is the sizes of the structures that dominate.…”

Section: Image Reconstructionsupporting

confidence: 80%

“…Additional details of the anechoic chamber as well as its validation can be found in Kerechanin et al [2001]. Details of the jet facility can be found in Hileman et al [2002] and Hileman [2004]. The jet nozzle had a 25.4 cm (1 inch) exit diameter and was designed using the method of characteristics for a Mach 1.3 flow.…”

Section: Jet Facility and Anechoic Chambermentioning

confidence: 99%

“…In Hileman and Samimy [2001], the acquisition of the acoustic field was accomplished with a dual microphone array for noise source location and the flow was captured via dual-pulse flow visualization. In Hileman et al [2002], this technique was greatly improved upon with a four-microphone inline array and the use of a temporally resolved flow visualization system. In this work, a 3-D microphone array was used to locate the noise origins while two flow visualization systems captured the dynamics of the jet.…”

Section: Introductionmentioning

confidence: 99%

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Correlation of Flow Structures and Radiated Noise in High Speed Jets

Samimy¹,

Hileman²,

Caraballo³

et al. 2004

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, search! the collection of information. Send comments regarding tNs burden estimate or any other aspect of tNs collection of information, including suggest!The dynamics of large-scale turbulence structures within a high Reynolds number, ideally expanded Mach 1.3 jet were investigated during both the periods of production of strong acoustic radiation and extended periods of relative quiet that lacked such acoustic radiation. These results were acquired through a unique experiment where the sources of large amplitude sound waves were estimated with a three-dunensional microphone array and the flow field was simultaneously visualized on two orthogonal planes. The images from one of the planes were taken at a 167 kHz rate. Proper Orthogonal Decomposition (POD) was employed to create a basis of the size and distribution of large-scale structures within the two planes. These POD modes were then used to objectively determine the differences in the jet structure during noise generation and periods lacking significant noise generation. The results show that the flow during the periods of relative quiet cases is dominated by the lower order POD modes that consist of relatively large turbulence structures while it is dominated by higher order POD modes that capture the dynamic mterplay of the large-scale structures durmg noise generation periods. For approximately one convective time scale prior to the moment of noise emission, a series of large-scale structures forms and disintegrates within the mixing layer and in the process a large amount of ambient fluid is entramed into the core of the jet. For the first time, these results show how the dynamic interplay of large-scale turbulence structures generates acoustic radiation within a high Reynolds number jet. SUBJECT TERMS ABSTRACTThe dynamics of large-scale turbulence structures within a high Reynolds number, ideally expanded Mach 1.3 jet were investigated during both the periods of production of strong acoustic radiation and extended periods of relative quiet that lacked such acoustic radiation. These results were acquired through a unique experiment where the sources of large amplitude sound waves were estimated with a three-dimensional microphone array and the flow field was simultaneously visualized on two orthogonal planes. The images from one of the planes were taken at a 167 kHz rate. Proper Orthogonal Decomposition (POD) was employed to create a basis of the size and distribution of large-scale structures within the two planes. These POD modes were then used to objectively determine the differences in the jet structure during noise generation and periods lacking significant noise generation. The results show that the flow during the periods of relative quiet cases is dominated by the lower order POD modes that consist of relatively large turbulence structures while it is dominated by higher order POD modes that cap...

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Section: Image Reconstructionsupporting

confidence: 80%

Section: Jet Facility and Anechoic Chambermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Correlation of Flow Structures and Radiated Noise in High Speed Jets

Samimy¹,

Hileman²,

Caraballo³

et al. 2004

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“…This produces a less efficient resonant system where no single mode locks in to dominate the spectrum. Figure 12, comparing the energy distribution in the time-frequency domain of the resonant and controlled Mach 0.3 flow obtained using the Mexican hat wavelet transformation discussed by Hileman et al, 38 supports this point. In the resonant case (Fig.…”

Section: Discussionsupporting

confidence: 60%

Logic-Based Active Control of Subsonic Cavity Flow Resonance

Debiasi

Samimy

2004

AIAA Journal

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We present the results of an experimental investigation for controlling a shallow cavity flow in the Mach number range 0.25-0.5. The flow exhibits the characteristic staging behavior predicted by the semi-empirical Rossiter formula with multiple modes in the Mach number range 0.32-0.38 and a single strong mode in other Mach numbers. A survey of the velocity at the exit of the zero net mass flow compression-driver actuator used for control reveals that its amplitude is frequency dependent and its behavior is little influenced by the main flow. Forcing the Mach 0.3 flow indicated that the actuator has good authority over a large range of frequencies, with reduction of spectral peaks observed at some forcing frequencies. We took advantage of this phenomenon to develop a logicbased controller that searches the frequency space and maintains the optimal forcing frequency for peak reduction at each Mach number. Optimal frequencies and the corresponding reduced resonance have been obtained for all of the flow conditions explored. The physics of optimal frequency forcing as well as some characteristics of the logic-based controller are discussed.

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“…The directivity of the direct correlation function is similar to the directivity of large turbulence structures noise. Hileman and coworkers (Hileman et al 2003(Hileman et al , 2004(Hileman et al , 2005 well as from large turbulence structures. It is observed in the present investigation that the dominant part of fine-scale turbulence noise source is located just downstream of the potential core of the jet.…”

Section: Resultsmentioning

confidence: 99%

The Sources of Jet Noise: Experimental Evidence

Tam¹,

Viswanathan

Ahuja

et al. 2007

13th AIAA/CEAS Aeroacoustics Conference (28th AIAA Aeroacoustics Conference)

106

174

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The primary objective of this investigation is to determine experimentally the sources of jet mixing noise. In the present study, four different approaches are used. It is reasonable to assume that the characteristics of the noise sources are imprinted on their radiation fields. Under this assumption, it becomes possible to analyse the characteristics of the far-field sound and then infer back to the characteristics of the sources. The first approach is to make use of the spectral and directional information measured by a single microphone in the far field. A detailed analysis of a large collection of far-field noise data has been carried out. The purpose is to identify special characteristics that can be linked directly to those of the sources. The second approach is to measure the coherence of the sound field using two microphones. The autocorrelations and cross-correlations of these measurements offer not only valuable information on the spatial structure of the noise field in the radial and polar angle directions, but also on the sources inside the jet. The third approach involves measuring the correlation between turbulence fluctuations inside a jet and the radiated noise in the far field. This is the most direct and unambiguous way of identifying the sources of jet noise. In the fourth approach, a mirror microphone is used to measure the noise source distribution along the lengths of high-speed jets. Features and trends observed in noise source strength distributions are expected to shed light on the source mechanisms. It will be shown that all four types of data indicate clearly the existence of two distinct noise sources in jets. One source of noise is the fine-scale turbulence and the other source is the large turbulence structures of the jet flow. Some of the salient features of the sound field associated with the two noise sources are reported in this paper.

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Exploring Noise Sources Using Simultaneous Acoustic Measurements and Real-Time Flow Visualizations in Jets

Cited by 30 publications

References 25 publications

Correlation of Flow Structures and Radiated Noise in High Speed Jets

Correlation of Flow Structures and Radiated Noise in High Speed Jets

Logic-Based Active Control of Subsonic Cavity Flow Resonance

The Sources of Jet Noise: Experimental Evidence

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