A Reconstruction Method for the Flow Past an Open Cavity

Podvin, Bérengère; Fraigneau, Yann; Lusseyran, François; Gougat, Pierre

doi:10.1115/1.2175159

Cited by 52 publications

(30 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These vortices are not symmetric in that the first eigenmode is characterized by a clockwise-rotating vortex, whereas the second eigenmode is featured by a counter-clockwise-rotating vortex. These structures bear a resemblance to the "wake" eigenmodes or the "pulsating" Taylor-Görtler-like vortices found in an open cavity flow that are known to produce certain frequencies, sounds, and oscillations (Pastur et al, 2005;Podvin et al, 2006;Rowley and Williams, 2006). When the air flows from the laryngopharynx to the supraglottic space, the esophageal space acts as an open cavity where vortices are formed both in the cavity (approximately corresponding to the left side of the solid lines above the bifurcation in Fig.…”

Section: Pod Analysismentioning

confidence: 77%

Characteristics of the turbulent laryngeal jet and its effect on airflow in the human intra-thoracic airways

Lin

Tawhai

McLennan

et al. 2007

Respiratory Physiology & Neurobiology

273

286

View full text Add to dashboard Cite

A computational fluid dynamics technique is applied to understand the relative importance of the upper and intra-thoracic airways and their role in determining central airflow patterns with particular attention paid to the importance of turbulence. The geometry of the human upper respiratory tract is derived from volumetric scans of a volunteer imaged via multidetector-row computed tomography. Geometry 1 consists of a mouth piece, the mouth, the oropharynx, the larynx, and the intra-thoracic airways of up to 6 generations. Geometry 2 comprises only the intra-thoracic airways. The results show that a curved sheet-like turbulent laryngeal jet is observed only in geometry 1 with turbulence intensity in the trachea varying from 10% to 20%, whereas the turbulence in geometry 2 is negligible. The presence of turbulence is found to increase the maximum localised wall shear stress by three folds. The proper orthogonal decomposition analysis reveals that the regions of high turbulence intensity are associated with Taylor-Görtler-like vortices. We conclude that turbulence induced by the laryngeal jet could significantly affect airway flow patterns as well as tracheal wall shear stress. Thus airflow modeling, particularly subject specific evaluations, should consider upper as well as intra-thoracic airway geometry.

show abstract

Section: Pod Analysismentioning

confidence: 77%

Characteristics of the turbulent laryngeal jet and its effect on airflow in the human intra-thoracic airways

Lin

Tawhai

McLennan

et al. 2007

Respiratory Physiology & Neurobiology

273

286

View full text Add to dashboard Cite

show abstract

“…Connection with previous numerical simulations Podvin et al (2006) and Chang et al (2006) also reported the formation of spanwise structures and low-frequency modulations, for incompressible flows over open cavities. Similar to our work, both numerical studies focused on a cavity of aspect ratio L/D = 2 with laminar incoming boundary layer and periodic conditions in the spanwise direction.…”

Section: Visual Evidence Of the Three-dimensional Modementioning

confidence: 99%

“…Using proper orthogonal decomposition (POD), Podvin et al (2006) investigated cavity flows at Re D = 4000, with L/θ 0 ≈ 75. They related the first two most energetic POD modes to the shear-layer instabilities, and the next three modes (significantly less energetic) to 'fluctuating vortex motions inside the cavity'.…”

Section: Visual Evidence Of the Three-dimensional Modementioning

confidence: 99%

“…Recently, some aspects of the three-dimensional cavity flow have been investigated using large-eddy simulation (LES) (Rizzetta & Visbal 2003;Larchevêque et al 2004;Chang, Constantinescu & Park 2006) and proper orthogonal decomposition (POD) (Podvin et al 2006). These studies have been focused on the frequencies of oscillation and coherence of the (two-dimensional) Rossiter modes, and the extent to which there is agreement with experimental measurements of mean flow and spectra.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Three-dimensional instabilities in compressible flow over open cavities

2008

View full text Add to dashboard Cite

Direct numerical simulations are performed to investigate the three-dimensional stability of compressible flow over open cavities. A linear stability analysis is conducted to search for three-dimensional global instabilities of the two-dimensional mean flow for cavities that are homogeneous in the spanwise direction. The presence of such instabilities is reported for a range of flow conditions and cavity aspect ratios. For cavities of aspect ratio (length to depth) of 2 and 4, the three-dimensional mode has a spanwise wavelength of approximately one cavity depth and oscillates with a frequency about one order of magnitude lower than two-dimensional Rossiter (flow/acoustics) instabilities. A steady mode of smaller spanwise wavelength is also identified for square cavities. The linear results indicate that the instability is hydrodynamic (rather than acoustic) in nature and arises from a generic centrifugal instability mechanism associated with the mean recirculating vortical flow in the downstream part of the cavity. These three-dimensional instabilities are related to centrifugal instabilities previously reported in flows over backward-facing steps, lid-driven cavity flows and Couette flows. Results from three-dimensional simulations of the nonlinear compressible Navier–Stokes equations are also reported. The formation of oscillating (and, in some cases, steady) spanwise structures is observed inside the cavity. The spanwise wavelength and oscillation frequency of these structures agree with the linear analysis predictions. When present, the shear-layer (Rossiter) oscillations experience a low-frequency modulation that arises from nonlinear interactions with the three-dimensional mode. The results are consistent with observations of low-frequency modulations and spanwise structures in previous experimental and numerical studies on open cavity flows.

show abstract

“…POD is today an established technique and many investigators have successfully used POD to analyze complex flow fields. Podvin et al (2006) used POD to investigate cavity flows and were able to relate the first couple of most the energetic and dominant POD modes to cavity flow shear layer instabilities. Meyer et al (2007) used PIV based POD to analyze flow structures in the JICF flow configuration.…”

Section: Introductionmentioning

confidence: 99%