東華大學圖書館 |

Language: English

Help

回圖書館首頁

手機版館藏查詢

Back

Switch To: Labeled | MARC Mode | ISBD

Modal Analysis of Harmonically Force...

Heidt, Liam Frank Raven,

Linked to FindBook

Google Book

Amazon

博客來

Modal Analysis of Harmonically Forced Turbulent Flows with Application to Jets /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Modal Analysis of Harmonically Forced Turbulent Flows with Application to Jets // Liam Frank Raven Heidt.
Author:	Heidt, Liam Frank Raven,
Description:	1 electronic resource (141 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-05, Section: A.
Contained By:	Dissertations Abstracts International86-05A.
Subject:	Aviation. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31657125
ISBN:	9798346397229

Modal Analysis of Harmonically Forced Turbulent Flows with Application to Jets /
Heidt, Liam Frank Raven,

Modal Analysis of Harmonically Forced Turbulent Flows with Application to Jets /Liam Frank Raven Heidt. - 1 electronic resource (141 pages)

Source: Dissertations Abstracts International, Volume: 86-05, Section: A.

Many turbulent flows exhibit time-periodic statistics. These include flows in turbomachinery, the wakes of bluff bodies, and flows exposed to harmonic actuation. However, many existing techniques for identifying and modeling coherent structures, most notably spectral proper orthogonal decomposition (SPOD) and resolvent analysis, assume statistical stationarity. In this thesis, we develop extensions to study turbulent flows with periodic statistics. We focus on the application of turbulent jets and jet noise reduction through harmonic actuation, which is of interest for both commercial and military aviation due to its success in reducing noise by up to 5 dB.To analyze the coherent structures in harmonically forced flows, we develop the cyclostationary spectral proper orthogonal decomposition (CS-SPOD). We examine the resulting properties of CS-SPOD and develop a theoretical connection between CS-SPOD and harmonic resolvent analysis (HRA), thereby providing the theoretical basis for HRA to be used as a model for coherent structures of cyclostationary flows. We develop and validate a computationally efficient algorithm and then illustrate its efficacy using the linearized (complex) Ginzburg-Landau equation.We next employ cyclostationary analysis to investigate the impact of an axisymmetric acoustic harmonic forcing on the mean, turbulence, and coherent structures of a round turbulent jet with a Mach number of 0.4 and a Reynolds number of 4.5 x 105. We perform large-eddy simulations for four cases at two forcing frequencies and amplitudes. Both low-frequency (Strouhal number of 0.3) and high-frequency (Strouhal number of 1.5) forcing is found to generate an energetic, nonlinear, tonal response consisting of the rollup of vortices via the Kelvin-Helmholtz mechanism. However, the impact of forcing on the broadband turbulence and coherent structures is limited, particularly at the low forcing amplitude associated with jet-noise-reduction devices. Additionally, the dominant coherent structures for the forced jets are similar in their energy, structure, and mechanism. At high forcing amplitudes, phase-dependent features arise in the dominant coherent structures and are associated with coupling to the high-velocity/shear regions of the mean. Overall, our results support the existing hypotheses that jet noise reduction can be associated with the deformation of the mean flow field rather than through direct interaction between the forcing and the turbulence. Lastly, we find that HRA predicts the dominant coherent structures well. This shows that HRA can be used to develop models of forced jets in a similar manner to how resolvent is employed for natural jets, which may be useful to guide future sound-source models of jets subjected to active control.

English

ISBN: 9798346397229Subjects--Topical Terms:

873136
Aviation.

Modal Analysis of Harmonically Forced Turbulent Flows with Application to Jets /
LDR:04120nmm a22003853i 4500 001 2432467
005 20250707081508.5
006 m o d
007 cr|nu||||||||
008 261011s2025 miu||||||m |||||||eng d
020 $a 9798346397229
035 $a (MiAaPQD)AAI31657125
035 $a (MiAaPQD)Caltech16619
035 $a AAI31657125
040 $a MiAaPQD $b eng $c MiAaPQD $e rda
100 1 $a Heidt, Liam Frank Raven, $e author. $3 3821699
245 1 0 $a Modal Analysis of Harmonically Forced Turbulent Flows with Application to Jets / $c Liam Frank Raven Heidt.
264 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2025
300 $a 1 electronic resource (141 pages)
336 $a text $b txt $2 rdacontent
337 $a computer $b c $2 rdamedia
338 $a online resource $b cr $2 rdacarrier
500 $a Source: Dissertations Abstracts International, Volume: 86-05, Section: A.
500 $a Advisors: Colonius, Tim Committee members: Bae, Jane; Blanquart, Guillaume; Sader, John.
502 $b Ph.D. $c California Institute of Technology $d 2025.
520 $a Many turbulent flows exhibit time-periodic statistics. These include flows in turbomachinery, the wakes of bluff bodies, and flows exposed to harmonic actuation. However, many existing techniques for identifying and modeling coherent structures, most notably spectral proper orthogonal decomposition (SPOD) and resolvent analysis, assume statistical stationarity. In this thesis, we develop extensions to study turbulent flows with periodic statistics. We focus on the application of turbulent jets and jet noise reduction through harmonic actuation, which is of interest for both commercial and military aviation due to its success in reducing noise by up to 5 dB.To analyze the coherent structures in harmonically forced flows, we develop the cyclostationary spectral proper orthogonal decomposition (CS-SPOD). We examine the resulting properties of CS-SPOD and develop a theoretical connection between CS-SPOD and harmonic resolvent analysis (HRA), thereby providing the theoretical basis for HRA to be used as a model for coherent structures of cyclostationary flows. We develop and validate a computationally efficient algorithm and then illustrate its efficacy using the linearized (complex) Ginzburg-Landau equation.We next employ cyclostationary analysis to investigate the impact of an axisymmetric acoustic harmonic forcing on the mean, turbulence, and coherent structures of a round turbulent jet with a Mach number of 0.4 and a Reynolds number of 4.5 x 105. We perform large-eddy simulations for four cases at two forcing frequencies and amplitudes. Both low-frequency (Strouhal number of 0.3) and high-frequency (Strouhal number of 1.5) forcing is found to generate an energetic, nonlinear, tonal response consisting of the rollup of vortices via the Kelvin-Helmholtz mechanism. However, the impact of forcing on the broadband turbulence and coherent structures is limited, particularly at the low forcing amplitude associated with jet-noise-reduction devices. Additionally, the dominant coherent structures for the forced jets are similar in their energy, structure, and mechanism. At high forcing amplitudes, phase-dependent features arise in the dominant coherent structures and are associated with coupling to the high-velocity/shear regions of the mean. Overall, our results support the existing hypotheses that jet noise reduction can be associated with the deformation of the mean flow field rather than through direct interaction between the forcing and the turbulence. Lastly, we find that HRA predicts the dominant coherent structures well. This shows that HRA can be used to develop models of forced jets in a similar manner to how resolvent is employed for natural jets, which may be useful to guide future sound-source models of jets subjected to active control.
546 $a English
590 $a School code: 0037
650 4 $a Aviation. $3 873136
650 4 $a Decomposition. $3 3561186
650 4 $a Eigenvalues. $3 631789
650 4 $a Energy. $3 876794
650 4 $a Fluid mechanics. $3 528155
650 4 $a Reynolds number. $3 3681436
650 4 $a Literature. $3 537498
690 $a 0204
690 $a 0791
690 $a 0401
710 2 $a California Institute of Technology. $b Engineering and Applied Science. $e degree granting institution. $3 3765818
720 1 $a Colonius, Tim $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-05A.
790 $a 0037
791 $a Ph.D.
792 $a 2025
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=31657125