Studying Sound Production in the Hole-Tone Configuration Using Compressible and Incompressible Global Stability Analyses

2021 ◽  
pp. 251-263
Author(s):  
R. Longobardi ◽  
D. Fabre ◽  
P. Bonnefis ◽  
V. Citro ◽  
F. Giannetti ◽  
...  
Keyword(s):  
Global Stability ◽  
Sound Production ◽  
Stability Analyses

scholarly journals Investigation of the roughness-induced transition: global stability analyses and direct numerical simulations

2014 ◽  
Vol 760 ◽  
pp. 175-211 ◽  
Author(s):  
Jean-Christophe Loiseau ◽  
Jean-Christophe Robinet ◽  
Stefania Cherubini ◽  
Emmanuel Leriche
Keyword(s):  
Aspect Ratio ◽  
Global Stability ◽  
Numerical Simulations ◽  
Shear Layer ◽  
Roughness Element ◽  
Three Dimensional ◽  
Direct Numerical Simulations ◽  
Low Speed ◽  
Stability Analyses ◽  
Roughness Elements

AbstractThe linear global instability and resulting transition to turbulence induced by an isolated cylindrical roughness element of height $h$ and diameter $d$ immersed within an incompressible boundary layer flow along a flat plate is investigated using the joint application of direct numerical simulations and fully three-dimensional global stability analyses. For the range of parameters investigated, base flow computations show that the roughness element induces a wake composed of a central low-speed region surrounded by a three-dimensional shear layer and a pair of low- and high-speed streaks on each of its sides. Results from the global stability analyses highlight the unstable nature of the central low-speed region and its crucial importance in the laminar–turbulent transition process. It is able to sustain two different global instabilities: a sinuous and a varicose one. Each of these globally unstable modes is related to a different physical mechanism. While the varicose mode has its root in the instability of the whole three-dimensional shear layer surrounding the central low-speed region, the sinuous instability turns out to be similar to the von Kármán instability in the two-dimensional cylinder wake and has its root in the lateral shear layers of the separated zone. The aspect ratio of the roughness element plays a key role on the selection of the dominant instability: whereas the flow over thin cylindrical roughness elements transitions due to a sinuous instability of the near-wake region, for larger roughness elements the varicose instability of the central low-speed region turns out to be the dominant one. Direct numerical simulations of the flow past an aspect ratio ${\it\eta}=1$ (with ${\it\eta}=d/h$) roughness element sustaining only the sinuous instability have revealed that the bifurcation occurring in this particular case is supercritical. Finally, comparison of the transition thresholds predicted by global linear stability analyses with the von Doenhoff–Braslow transition diagram provides qualitatively good agreement.

scholarly journals A global analysis of tonal noise in flows around aerofoils

2014 ◽  
Vol 754 ◽  
pp. 5-38 ◽  
Author(s):  
Miguel Fosas de Pando ◽  
Peter J. Schmid ◽  
Denis Sipp
Keyword(s):  
Global Stability ◽  
Acoustic Radiation ◽  
Global Analysis ◽  
Feedback Loops ◽  
Surface Boundary ◽  
Mean Flow ◽  
Suction Surface ◽  
Stability Analyses ◽  
Pressure Surface ◽  
Linearized Operator

AbstractThe generation of discrete acoustic tones in the compressible flow around an aerofoil is addressed in this work by means of nonlinear numerical simulations and global stability analyses. The nonlinear simulations confirm the appearance of discrete tones in the acoustic spectrum and, for the chosen flow case, the global stability analyses of the mean-flow dynamics reveal that the linearized operator is stable. However, the flow response to incoming disturbances exhibits important transient growth effects that culminate in the onset of aeroacoustic feedback loops, involving instability processes on the suction- and pressure-surface boundary layers together with their cross-interaction by acoustic radiation at the trailing edge. The features of the aeroacoustic feedback loops and the appearance of discrete tones are then related to the features of the least-stable modes in the global spectrum: the spatial structure of the direct modes displays the coupled dynamics of hydrodynamic instabilities on the suction surface and in the near wake. Finally, different families of global modes will be identified and the dynamics that they represent will be discussed.

Large eddy simulations and global stability analyses of an annular and cylindrical rotor/stator cavity limit cycles

2019 ◽  
Vol 31 (10) ◽  
pp. 104109 ◽  
Author(s):  
Matthieu Queguineur ◽  
Thibault Bridel-Bertomeu ◽  
Laurent Y. M. Gicquel ◽  
Gabriel Staffelbach
Keyword(s):  
Global Stability ◽  
Limit Cycles ◽  
Large Eddy Simulations ◽  
Stability Analyses ◽  
Large Eddy

scholarly journals Global Stability Analyses Unraveling Roughness-induced Transition Mechanisms

2015 ◽  
Vol 14 ◽  
pp. 182-191 ◽  
Author(s):  
J.-Ch. Loiseau ◽  
J.-Ch. Robinet ◽  
S. Cherubini ◽  
E. Leriche
Keyword(s):  
Global Stability ◽  
Stability Analyses

Reading Risk in Children With Speech Sound Disorder: Prevalence, Persistence, and Predictors

2020 ◽  
Vol 63 (11) ◽  
pp. 3714-3726
Author(s):  
Sherine R. Tambyraja ◽  
Kelly Farquharson ◽  
Laura Justice
Keyword(s):  
At Risk ◽  
Sound Production ◽  
Speech Therapy ◽  
Speech Sound ◽  
Reading Difficulties ◽  
School Age Children ◽  
Speech Sound Disorder ◽  
Word Decoding ◽  
School Year ◽  
School Based

Purpose The purpose of this study was to determine the extent to which school-age children with speech sound disorder (SSD) exhibit concomitant reading difficulties and examine the extent to which phonological processing and speech production abilities are associated with increased likelihood of reading risks. Method Data were obtained from 120 kindergarten, first-grade, and second-grade children who were in receipt of school-based speech therapy services. Children were categorized as being “at risk” for reading difficulties if standardized scores on a word decoding measure were 1 SD or more from the mean. The selected predictors of reading risk included children's rapid automatized naming ability, phonological awareness (PA), and accuracy of speech sound production. Results Descriptive results indicated that just over 25% of children receiving school-based speech therapy for an SSD exhibited concomitant deficits in word decoding and that those exhibiting risk at the beginning of the school year were likely to continue to be at risk at the end of the school year. Results from a hierarchical logistic regression suggested that, after accounting for children's age, general language abilities, and socioeconomic status, both PA and speech sound production abilities were significantly associated with the likelihood of being classified as at risk. Conclusions School-age children with SSD are at increased risk for reading difficulties that are likely to persist throughout an academic year. The severity of phonological deficits, reflected by PA and speech output, may be important indicators of subsequent reading problems.

Sound Production Treatment for Acquired Apraxia of Speech: An Examination of Dosage in Relation to Probe Performance

2020 ◽  
pp. 1-16
Author(s):  
Julie L. Wambaugh ◽  
Lydia Kallhoff ◽  
Christina Nessler
Keyword(s):  
Retrospective Analysis ◽  
Sound Production ◽  
Apraxia Of Speech ◽  
Practice Schedule ◽  
Practice Schedules ◽  
Baseline Performance ◽  
The Mean ◽  
Number Of Treatment ◽  
The Impact

Purpose This study was designed to examine the association of dosage and effects of Sound Production Treatment (SPT) for acquired apraxia of speech. Method Treatment logs and probe data from 20 speakers with apraxia of speech and aphasia were submitted to a retrospective analysis. The number of treatment sessions and teaching episodes was examined relative to (a) change in articulation accuracy above baseline performance, (b) mastery of production, and (c) maintenance. The impact of practice schedule (SPT-Blocked vs. SPT-Random) was also examined. Results The average number of treatment sessions conducted prior to change was 5.4 for SPT-Blocked and 3.9 for SPT-Random. The mean number of teaching episodes preceding change was 334 for SPT-Blocked and 179 for SPT-Random. Mastery occurred within an average of 13.7 sessions (1,252 teaching episodes) and 12.4 sessions (1,082 teaching episodes) for SPT-Blocked and SPT-Random, respectively. Comparisons of dosage metric values across practice schedules did not reveal substantial differences. Significant negative correlations were found between follow-up probe performance and the dosage metrics. Conclusions Only a few treatment sessions were needed to achieve initial positive changes in articulation, with mastery occurring within 12–14 sessions for the majority of participants. Earlier occurrence of change or mastery was associated with better follow-up performance. Supplemental Material https://doi.org/10.23641/asha.12592190

Item Context and /s/ Phone Articulation Test Results

1972 ◽  
Vol 15 (4) ◽  
pp. 852-860 ◽  
Author(s):  
Zoe Zehel ◽  
Ralph L. Shelton ◽  
William B. Arndt ◽  
Virginia Wright ◽  
Mary Elbert
Keyword(s):  
Test Score ◽  
Sound Production ◽  
Broad Context ◽  
Test Results ◽  
Production Task ◽  
Test Result

Fourteen children who misarticulated some phones of the /s/ phoneme were tape recorded articulating several lists of items involving /s/. The lists included the Mc-Donald Deep Test for /s/, three lists similar to McDonald’s but altered in broad context, and an /s/ sound production task. Scores from lists were correlated, compared for differences in means, or both. Item sets determined by immediate context were also compared for differences between means. All lists were found to be significantly correlated. The comparison of means indicated that both broad and immediate context were related to test result. The estimated “omega square” statistic was used to evaluate the percentage of test score variance attributable to context.

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