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Direct Computation of Wall-Pressure ...

Liu, Yi,

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Direct Computation of Wall-Pressure Fluctuations in Weakly Compressible Turbulent Wall-Bounded Flows /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Direct Computation of Wall-Pressure Fluctuations in Weakly Compressible Turbulent Wall-Bounded Flows // Yi Liu.
Author:	Liu, Yi,
Description:	1 electronic resource (202 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-12, Section: B.
Contained By:	Dissertations Abstracts International85-12B.
Subject:	Fluid mechanics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31235370
ISBN:	9798382723167

Direct Computation of Wall-Pressure Fluctuations in Weakly Compressible Turbulent Wall-Bounded Flows /
Liu, Yi,

Direct Computation of Wall-Pressure Fluctuations in Weakly Compressible Turbulent Wall-Bounded Flows /Yi Liu. - 1 electronic resource (202 pages)

Source: Dissertations Abstracts International, Volume: 85-12, Section: B.

Knowledge of wall-pressure fluctuations in turbulent wall-bounded flows is important for predictions of structural vibration and noise. In this study, compressible direct numerical simulations with a sixth-order, non-dissipative finite difference scheme are employed to accurately capture the spatiotemporal characteristics of wall-pressure fluctuations in low-Mach-number turbulent wall-bounded flows. Turbulent channel flow simulations are conducted at bulk Mach numbers Mb = 0.4, 0.2 and 0.1, and friction Reynolds number Reτ = 180. In addition to the convective ridge that is virtually Mach number independent, acoustic ridges, whose magnitudes are orders of magnitude lower, are identified in the two-dimensional wavenumber-frequency spectrum. At lower frequencies, the acoustic ridges represent propagating longitudinal and oblique waves that match the theoretical predictions of two-dimensional duct modes with a uniform mean flow. They decay with decreasing Mach numbers but remain distinctly identifiable even at Mb = 0.1. At high frequencies, in contrast, no propagating waves are found, and the spectral level in the supersonic wavenumber range is broadly elevated and increases with decreasing Mach number.At Mb = 0.4, two additional simulations are carried out, one in a plane channel at Reτ = 500 to explore the Reynolds number effect, and the other in a channel with a surface hump at friction Reτ = 180 to examine the impact of surface inhomogeneity. A strong Reynolds number dependence is observed in the subconvective wavenumber region, where the spectral level shows a significant elevation with increasing Reynolds number, especially at higher frequencies. The presence of the small two-dimensional hump along the spanwise direction is shown to vastly increase the acoustic energy for both longitudinal and oblique modes as well as the broadband subconvective spectral level as a result of diffraction and turbulence generation induced by the hump.Moreover, the fluctuating wall pressure beneath a flat-plate turbulent boundary layer is investigated at M∞ = 0.4 and momentum-thickness Reynolds numbers Reθ up to 1918. The results reveal the presence of acoustic ridges associated with longitudinally propagating waves in the two-dimensional wavenumber-frequency spectra. These acoustic ridges are less prominent compared with their counterparts in the plane channel. With proper frequency scaling, the convective ridges in TBL and plane-channel flows are found to be nearly identical. A small two-dimensional surface hump is found to substantially increase the acoustic energy for the downstream propagating waves downstream of the hump, but has less impact on the upstream region.

English

ISBN: 9798382723167Subjects--Topical Terms:

528155
Fluid mechanics.
Subjects--Index Terms:

Aeroacoustics

Direct Computation of Wall-Pressure Fluctuations in Weakly Compressible Turbulent Wall-Bounded Flows /
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300 $a 1 electronic resource (202 pages)
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500 $a Source: Dissertations Abstracts International, Volume: 85-12, Section: B.
500 $a Advisors: Wang, Meng Committee members: MacArt, Jonathan; Morris, Scott; Thomas, Flint.
502 $b Ph.D. $c University of Notre Dame $d 2024.
520 $a Knowledge of wall-pressure fluctuations in turbulent wall-bounded flows is important for predictions of structural vibration and noise. In this study, compressible direct numerical simulations with a sixth-order, non-dissipative finite difference scheme are employed to accurately capture the spatiotemporal characteristics of wall-pressure fluctuations in low-Mach-number turbulent wall-bounded flows. Turbulent channel flow simulations are conducted at bulk Mach numbers Mb = 0.4, 0.2 and 0.1, and friction Reynolds number Reτ = 180. In addition to the convective ridge that is virtually Mach number independent, acoustic ridges, whose magnitudes are orders of magnitude lower, are identified in the two-dimensional wavenumber-frequency spectrum. At lower frequencies, the acoustic ridges represent propagating longitudinal and oblique waves that match the theoretical predictions of two-dimensional duct modes with a uniform mean flow. They decay with decreasing Mach numbers but remain distinctly identifiable even at Mb = 0.1. At high frequencies, in contrast, no propagating waves are found, and the spectral level in the supersonic wavenumber range is broadly elevated and increases with decreasing Mach number.At Mb = 0.4, two additional simulations are carried out, one in a plane channel at Reτ = 500 to explore the Reynolds number effect, and the other in a channel with a surface hump at friction Reτ = 180 to examine the impact of surface inhomogeneity. A strong Reynolds number dependence is observed in the subconvective wavenumber region, where the spectral level shows a significant elevation with increasing Reynolds number, especially at higher frequencies. The presence of the small two-dimensional hump along the spanwise direction is shown to vastly increase the acoustic energy for both longitudinal and oblique modes as well as the broadband subconvective spectral level as a result of diffraction and turbulence generation induced by the hump.Moreover, the fluctuating wall pressure beneath a flat-plate turbulent boundary layer is investigated at M∞ = 0.4 and momentum-thickness Reynolds numbers Reθ up to 1918. The results reveal the presence of acoustic ridges associated with longitudinally propagating waves in the two-dimensional wavenumber-frequency spectra. These acoustic ridges are less prominent compared with their counterparts in the plane channel. With proper frequency scaling, the convective ridges in TBL and plane-channel flows are found to be nearly identical. A small two-dimensional surface hump is found to substantially increase the acoustic energy for the downstream propagating waves downstream of the hump, but has less impact on the upstream region.
546 $a English
590 $a School code: 0165
650 4 $a Fluid mechanics. $3 528155
650 4 $a Acoustics. $3 879105
650 4 $a Mechanical engineering. $3 649730
653 $a Aeroacoustics
653 $a Flow-structure interactions
653 $a Turbulence simulation
653 $a Acoustic ridges
690 $a 0204
690 $a 0986
690 $a 0548
710 2 $a University of Notre Dame. $b Aerospace and Mechanical Engineering. $e degree granting institution. $3 3823055
720 1 $a Wang, Meng $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-12B.
790 $a 0165
791 $a Ph.D.
792 $a 2024
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31235370