Mitigation of impinging tones using central protrusion

Dhamanekar, Abhijit; Srinivasan, K.

doi:10.1016/j.jsv.2018.07.002

Cited by 6 publications

(2 citation statements)

References 29 publications

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“…Dhamanekar and Srinivasan's findings revealed that the central protrusion on the impinging plate exhibits greater efficacy in attenuating tones within supersonic impinging jets compared to those present in subsonic impinging jets. 38 Recently, Lubert et al 39 conducted a comprehensive review of the research conducted by NASA over the past 50 years on the physics underlying the generation and mitigation of noise from launch vehicles. Different noise reduction techniques for impinging jets can be found in the review articles of Jiang et al, 5 and Salehian and Mankbadi.…”

Section: Introduction and State Of The Artmentioning

confidence: 99%

Acoustic characteristics of jets impinging on permeable plates

Dhamanekar,

Srinivasan

2023

International Journal of Aeroacoustics

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This article explores the acoustic characteristics and the relevant flow features of jets impinging on permeable plates. Noise generated due to the interaction of the jet with permeable plates is compared with jets impinging on an impermeable plate and the corresponding free jet. This study systematically measures various parameters, including pore size, porosity, and pressure drop, to precisely quantify the permeability of the plates using the Forchheimer equation. The focus is on investigating the impact of permeability on noise reduction. An acoustic study is performed by carrying out blow-up and blow-down tests to find the effect of permeability at different nozzle pressure ratios and different nozzle-plate spacings. An extensive directivity study is conducted to find the directionality of acoustic emissions and calculate acoustic power. It is found that the overall sound pressure level is lower for the jets impinging on the permeable plates compared to the impermeable plates in subsonic cases. It is also observed that the insertion of the permeable plates in supersonic jets generates less noise compared to the corresponding free jet. It is found that most of the tones are absent in the case of permeable plates for supersonic jets, whereas the tones are present with lesser amplitude compared to jets impinging on impermeable plates for subsonic and transonic jets. Finally, flow measurement and flow visualization studies are carried out to understand the flow physics responsible for the noise variance. This study illuminates that the passage of flow through the porous plate results in the reduction of wall-jet velocities, thereby suppressing the turbulent mixing noise. The absence of shock oscillations in front of the permeable plate is identified as the cause of the mitigation of impinging tones.

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Section: Introduction and State Of The Artmentioning

confidence: 99%

Acoustic characteristics of jets impinging on permeable plates

Dhamanekar,

Srinivasan

2023

International Journal of Aeroacoustics

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“…Here, the interactions especially during supersonic gas jet impingement on solid surfaces are well documented, e.g. in [1][2][3]. In such situations, only the gas flow field is highly dynamic and the shape of the surface does not change.…”

Section: Introductionmentioning

confidence: 99%

A new experimental setup for time-resolved measurements of interactions between gas jets and flexible surfaces

Burkert

Schwarze

2022

Meas. Sci. Technol.

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The purpose of this study was to present a new setup for time-resolved measurements of the interactions between gas jets and ﬂexible surfaces. Such interactions are dominated by characteristic surface deformations and gas-driven surface waves. Previous works have studied the gas-surface interaction only in a sectional plane but not as a three-dimensional problem. In our setup, surface deformations and waves were generated by the impingement of a supersonic jet on a ﬂexible surface made of a silicon membrane. The inlet pressure of the Laval nozzle was varied from 0.8 bar to 3 bar and the nozzle surface distance was set in the range of 30 mm to 120mm with respect to the ﬂat surface. The entire surface area and its behavior were recorded using a high-speed camera. The evaluation was based on the pixel intensity values of the recorded surface images during the jet impingement. A fast Fourier transformation was applied to the results to determine the dominant frequencies of surface movements in detail. From this, low- and high-frequency events on the surface can be derived. Correlations between the main process parameters, nozzle distance, nozzle inlet pressure and characteristic surface behavior were deduced and mapped.

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