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Numerical Investigations of Supersonic Cavity Flows With Effect of Doors /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Numerical Investigations of Supersonic Cavity Flows With Effect of Doors // Skyler Keil Baugher.
Author:	Baugher, Skyler Keil,
Description:	1 electronic resource (255 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 87-05, Section: B.
Contained By:	Dissertations Abstracts International87-05B.
Subject:	Physics. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32384084
ISBN:	9798297964235

Numerical Investigations of Supersonic Cavity Flows With Effect of Doors /
Baugher, Skyler Keil,

Numerical Investigations of Supersonic Cavity Flows With Effect of Doors /Skyler Keil Baugher. - 1 electronic resource (255 pages)

Source: Dissertations Abstracts International, Volume: 87-05, Section: B.

Cavity flows are a common geometric feature in various applications, including musical instruments, motor vehicles, and various aircraft applications. In these latter uses, the resulting flow engenders significant acoustic loading, surpassing even 160db, damaging vital equipment, causing structural damage, loss of stealth and even failed store trajectories. The dynamics are predominately influenced by non-linear shear layer dynamics, which display 3-dimensional phenomena including spillage vortices, recirculation and large ultra-low frequency structures, such as the tornado vortex. The low frequency structures result from a quasi-periodic bifurcation of the shear layer, whose modulation, under certain conditions, plays a significant role in introducing span wise asymmetry of the cavity. The introduction of doors, such as on fighter aircraft or landing gear bays, introduces additional 3-dimensional interactions between the doors, shear layer, and low frequency cavity dynamics. As a result, dynamic loading may increase by up to 20db, stemming from complex 3-dimensional interactions such as the trapping of acoustic waves and changes in the features of spillage vortices or shear layer development.Despite the large number of applications and complex dynamics of cavity flows, which are not fully understood, studies in literature regarding low frequency 3-dimensional dynamics and shear layer bifurcation are relatively scarce. The few comprehensive studies of these phenomena are generally in low speed situations, whose low Reynolds numbers, aspect ratios and boundary conditions contain dynamics that are not readily extended to higher speed flows. Even fewer studies have included the implementation of doors, which significantly intensify and complicate the above phenomena; door operation (opening and closing) introduces transient effects that lead to be non-statistically stationary observations.These gaps in literature are addressed in the present thesis through computations, performed in parallel with experimental efforts at Florida State University. Supersonic cavity flows (Mach 2 and 1.6) with aspect ratios 4.5:1:1 (L:D:W) are considered for concreteness. This study includes the implementation of doors; for generality sliding, blunt and wedge doors are considered. To obtain results in an effective manner, differing degrees of computational fidelity are applied when necessary, namely RANS, hybrid RANS/LES and LES methodologies. Aside from the novel simulations performed, complex physics-driven methods and a myriad of data driven methods (e.g. Dynamic Mode Decomposition) are applied to the 3-dimensional flow field to isolate key dynamics associated with high-speed flows. In particular, they elucidate the interactions between the shear layer and ultra-low frequency 3-dimensional cavity motions and their effect of acoustic resonance. Furthermore, how these interactions, 3-dimensional structures and acoustic interactions are investigated with doors along with transient effects such as resonance startup with door operation.Key findings include the bifurcated state of the shear layer causing asymmetry in the cavity, its effects on flow acoustic resonance in the cavity, and the hydrodynamic and acoustic responses in the baseline no doors (ND) cavity and door configurations. It was found that the baseline cavity exhibits shear layer bifurcation, where the shear layer has a quasi-periodic impingement preference on one side of the back wall. This results in significantly asymmetric flow structures within the cavity, which in turn interact with the shear layer and modulate the resonance process. The most prominent structure within the cavity is the tornado vortex, which appears upstream of the cavity swirling fluid back into the shear layer. Upon investigating door configurations, the observed shear layer bifurcation and asymmetry persist, manifesting in similar tornado vortex structures with the wedge doors, and a 'twin-tornado' vortex system in the sliding doors and certain door angles. Ultimately, it was found that physical connections can established between the baseline and door configurations by observing the pressure distributions on the back wall. This was shown using long-time series Delayed Detached Eddy Simulations (DDES) simulation was able to confirm the effect of the asymmetry observed in RANS and its role in flow-acoustic resonance. A conglomerate of data driven methods, such as Dynamic Mode Decomposition (DMD), was applied to full volume snapshots of the cavity, fully isolating the quasi-periodic motion of bifurcated shear layer and the resulting 3-dimensional structures in the cavity, such as the tornado vortex for the first time. Furthermore, Momentum Potential Theory (MPT) was implemented on the baseline and door configurations segregating the hydrodynamic and acoustic components of the flow field. The nearly 20db increase of sound pressure levels in the cavity, were accompanied by tonal shifts in the door configurations and the presence of new dominant tones. It was revealed that the acoustic response near the was directly correlated with that of the impingement of hydrodynamic structures through the use of a multi-variate Spectral Proper Orthogonal Decomposition (SPOD) .This implies that a different interpretation of phase lag in the Rossiter formula may be warranted, and that 3-dimensional effects must be accounted for.

English

ISBN: 9798297964235Subjects--Topical Terms:

516296
Physics.
Subjects--Index Terms:

Cavity flows

Numerical Investigations of Supersonic Cavity Flows With Effect of Doors /
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502 $b Ph.D. $c The Ohio State University $d 2025.
520 $a Cavity flows are a common geometric feature in various applications, including musical instruments, motor vehicles, and various aircraft applications. In these latter uses, the resulting flow engenders significant acoustic loading, surpassing even 160db, damaging vital equipment, causing structural damage, loss of stealth and even failed store trajectories. The dynamics are predominately influenced by non-linear shear layer dynamics, which display 3-dimensional phenomena including spillage vortices, recirculation and large ultra-low frequency structures, such as the tornado vortex. The low frequency structures result from a quasi-periodic bifurcation of the shear layer, whose modulation, under certain conditions, plays a significant role in introducing span wise asymmetry of the cavity. The introduction of doors, such as on fighter aircraft or landing gear bays, introduces additional 3-dimensional interactions between the doors, shear layer, and low frequency cavity dynamics. As a result, dynamic loading may increase by up to 20db, stemming from complex 3-dimensional interactions such as the trapping of acoustic waves and changes in the features of spillage vortices or shear layer development.Despite the large number of applications and complex dynamics of cavity flows, which are not fully understood, studies in literature regarding low frequency 3-dimensional dynamics and shear layer bifurcation are relatively scarce. The few comprehensive studies of these phenomena are generally in low speed situations, whose low Reynolds numbers, aspect ratios and boundary conditions contain dynamics that are not readily extended to higher speed flows. Even fewer studies have included the implementation of doors, which significantly intensify and complicate the above phenomena; door operation (opening and closing) introduces transient effects that lead to be non-statistically stationary observations.These gaps in literature are addressed in the present thesis through computations, performed in parallel with experimental efforts at Florida State University. Supersonic cavity flows (Mach 2 and 1.6) with aspect ratios 4.5:1:1 (L:D:W) are considered for concreteness. This study includes the implementation of doors; for generality sliding, blunt and wedge doors are considered. To obtain results in an effective manner, differing degrees of computational fidelity are applied when necessary, namely RANS, hybrid RANS/LES and LES methodologies. Aside from the novel simulations performed, complex physics-driven methods and a myriad of data driven methods (e.g. Dynamic Mode Decomposition) are applied to the 3-dimensional flow field to isolate key dynamics associated with high-speed flows. In particular, they elucidate the interactions between the shear layer and ultra-low frequency 3-dimensional cavity motions and their effect of acoustic resonance. Furthermore, how these interactions, 3-dimensional structures and acoustic interactions are investigated with doors along with transient effects such as resonance startup with door operation.Key findings include the bifurcated state of the shear layer causing asymmetry in the cavity, its effects on flow acoustic resonance in the cavity, and the hydrodynamic and acoustic responses in the baseline no doors (ND) cavity and door configurations. It was found that the baseline cavity exhibits shear layer bifurcation, where the shear layer has a quasi-periodic impingement preference on one side of the back wall. This results in significantly asymmetric flow structures within the cavity, which in turn interact with the shear layer and modulate the resonance process. The most prominent structure within the cavity is the tornado vortex, which appears upstream of the cavity swirling fluid back into the shear layer. Upon investigating door configurations, the observed shear layer bifurcation and asymmetry persist, manifesting in similar tornado vortex structures with the wedge doors, and a 'twin-tornado' vortex system in the sliding doors and certain door angles. Ultimately, it was found that physical connections can established between the baseline and door configurations by observing the pressure distributions on the back wall. This was shown using long-time series Delayed Detached Eddy Simulations (DDES) simulation was able to confirm the effect of the asymmetry observed in RANS and its role in flow-acoustic resonance. A conglomerate of data driven methods, such as Dynamic Mode Decomposition (DMD), was applied to full volume snapshots of the cavity, fully isolating the quasi-periodic motion of bifurcated shear layer and the resulting 3-dimensional structures in the cavity, such as the tornado vortex for the first time. Furthermore, Momentum Potential Theory (MPT) was implemented on the baseline and door configurations segregating the hydrodynamic and acoustic components of the flow field. The nearly 20db increase of sound pressure levels in the cavity, were accompanied by tonal shifts in the door configurations and the presence of new dominant tones. It was revealed that the acoustic response near the was directly correlated with that of the impingement of hydrodynamic structures through the use of a multi-variate Spectral Proper Orthogonal Decomposition (SPOD) .This implies that a different interpretation of phase lag in the Rossiter formula may be warranted, and that 3-dimensional effects must be accounted for.
546 $a English
590 $a School code: 0168
650 4 $a Physics. $3 516296
650 4 $a Computer engineering. $3 621879
650 4 $a Aerospace engineering. $3 1002622
650 4 $a Fluid mechanics. $3 528155
653 $a Cavity flows
653 $a Detached Eddy Simulations
653 $a Momentum Potential Theory
653 $a Spectral Proper Orthogonal Decomposition
653 $a Dynamic Mode Decomposition
690 $a 0538
690 $a 0605
690 $a 0464
690 $a 0204
710 2 $a The Ohio State University. $b Aerospace Engineering. $e degree granting institution. $3 3829383
720 1 $a Gaitonde, Datta $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 87-05B.
790 $a 0168
791 $a Ph.D.
792 $a 2025
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32384084