Proper Orthogonal Decomposition for Experimental Investigation of Flame Instabilities

Iudiciani, Piero; Duwig, Christophe; Hosseini, Seyed Mohammad; Szász, Róbert-Zoltán; Fuchs, László; Gutmark, Ephraim

doi:10.2514/1.j051297

Cited by 31 publications

(13 citation statements)

References 39 publications

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“…In the present case, the mode pair amplitudes depicted in Fig. 6a do not have a circumferential distribution, but fill a circular disk in the normalized amplitude plane, which can be due to amplitude [16] and/or frequency modulation [8]. The phasing ϕ n of each snapshot can now be extracted from the normalized amplitude plane via the four-quadrant inverse tangent: Figure 6b shows the fluctuation velocity in y direction (V -component) of an average of snapshots within a 15…”

Section: Resultsmentioning

confidence: 59%

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Experimental Investigations of Tonal Noise on a Vehicle Side Mirror

Werner

Würz

Krämer

2016

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Experimental investigations on an isolated vehicle side mirror model are performed in a low turbulence wind tunnel aiming at the identification of the acoustic source mechanism leading to tonal noise emission. A combination of acoustic measurements and Particle Image Velocimetry shows that the discrete frequency noise can be related to the presence of a laminar boundary layer separation extending up to the trailing edge on the mirror's side surface and upper side. In the vicinity of the trailing edge, the shear layer develops into a vortical structure, which impinges on the trailing edge. By utilization of Proper Orthogonal Decomposition on the ensembles of instantaneous velocity fields and application of a phase sorting method, the length scales of the vortical structures could be extracted and related to the acoustic radiation. Order of magnitude analyses show parallels to the acoustic feedback mechanism known from the NACA 0012 airfoil.

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Section: Resultsmentioning

confidence: 59%

“…A pair of POD modes allows to assign a particular phasing to each snapshot of an ensemble with no need of a reference signal and even when the data acquisition time is not time resolved with respect to the expected signal frequency [8,16,19]. As the weighting factors a n, j can be interpreted as the amplitude of each POD mode Fig.…”

Section: Resultsmentioning

confidence: 99%

Experimental Investigations of Tonal Noise on a Vehicle Side Mirror

Werner

Würz

Krämer

2016

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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“…Visualization techniques are developed and applied to investigate the combustion instability [8,9,[11][12][13]. The representative flow visualization technique is PIV but it requires the incorporation of complex equipment and technical experiences.…”

Section: Introductionmentioning

confidence: 99%

“…The flame structure captured by these optical measurements includes information regarding the temperature field of the flow, thus crudely approximate the streak-line of the flow. Iudiciani et al [11] compared the visualization results of two different techniques, direct imaging and OH radical Chemiluminescence. The results showed similar structures showing a comparably simple convenient direct imaging could capture the important flow dynamics with compensation on the accuracy.…”

Section: Introductionmentioning

confidence: 99%

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The change in flow dynamics inside the post chamber of hybrid rocket

Choi

Lee

2015

J Mech Sci Technol

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Visualization of the flow field inside the post chamber of hybrid rocket has been conducted with direct imaging technique. It has been suggested that the flow dynamics inside the post chamber of hybrid rocket strongly affects the occurrence of Low frequency instability (LFI). Conventional observations of pressure and temperature measurements are insufficient to investigate the flow dynamics, thereby the visualization was applied. Direct imaging was used and the simple inexpensive method showed its capability of capturing interesting flow dynamics at reduced accuracy. First of all, in-phase like behavior between the unsteady heat release approximated by luminosity fluctuation and pressure oscillation has been confirmed. The coupling mechanism between local heat release and pressure oscillation of non-acoustic instability would lie in the hydrodynamics. Further analysis was done on visualized flow field with Proper orthogonal decomposition. The difference due to the existence of LFI was repeatedly appeared in mode 3 analysis. As a result, it is suggested that mode 2 and 3 interaction generates a rotating motion. The frequency characteristic of the rotating motion is found to be at a higher frequency than the most dominant frequency in the vicinity of 20 Hz. It is suspected that this rotating motion is closely related to vortex generation and is seemed to share similar characteristics to the Benard-von Karman instability found in bluff-body combustions. Investigations will be extended to the previously found cases of instability occurred experiments to understand the change in flow dynamics due to LFI.

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