Influence of Expansion Ratio and Turbulence Modeling on the Acoustic Characteristics of Ducted Premixed Combustion

2008 ◽  
Author(s):  
Tek Seang Kuan ◽  
R. Peter Lindstedt
Keyword(s):  
Turbulence Modeling ◽  
Expansion Ratio ◽  
Premixed Combustion ◽  
Acoustic Characteristics

LATTICE-BOLTZMANN SIMULATIONS OF FLOWS OVER BACKWARD-FACING INCLINED STEPS

2013 ◽  
Vol 25 (01) ◽  
pp. 1340021 ◽  
Author(s):  
RUPESH B. KOTAPATI ◽  
RICHARD SHOCK ◽  
HUDONG CHEN
Keyword(s):  
Turbulent Flows ◽  
Lattice Boltzmann ◽  
Turbulence Modeling ◽  
Laser Doppler Anemometry ◽  
Expansion Ratio ◽  
Outlet Section ◽  
Inlet Section ◽  
Eddy Simulation ◽  
Lattice Boltzmann Simulations ◽  
Inclination Angles

The lattice-Boltzmann method (LBM) is used in conjunction with a very large-eddy simulation (VLES) turbulence modeling approach to compute separated flows over backward-facing steps at different wall inclination angles. The Reynolds number Re H based on the step height H and center-line velocity at the channel inlet ucl is 64 000. The expansion ratio of the outlet section to the inlet section of the channel is 1.48. Wall inclination angles α considered include 10°, 15°, 20°, 25°, 30° and 90°. The computed flow fields for different inclination angles of the step are assessed against the laser Doppler anemometry (LDA) measurements of Makiola [B. Makiola, Ph.D. Thesis, University of Karlsruhe (1992); B. Ruck and B. Makiola, Flow separation over the step with inclined walls, in Near-Wall Turbulent Flows, eds. R. M. C. So, C. G. Speziale and B. E. Launder (Elsevier, 1993), p. 999.]. In addition to validating the lattice-Boltzmann solution with the experiments, this study also investigates the effects of three dimensionality, the proximity of the inlet to the step, and the grid resolution on the quality of the predictions.

Influence of Hydrogen Addition on Lean Premixed Methane-Air Flame Statistics

2010 ◽  
Author(s):  
Baris Yilmaz ◽  
Sibel O¨zdogan ◽  
Iskender Go¨kalp
Keyword(s):  
High Pressure ◽  
Software Package ◽  
Turbulence Modeling ◽  
Laminar Flame ◽  
Turbulent Flame ◽  
Premixed Combustion ◽  
High Pressure Chamber ◽  
Hydrogen Addition ◽  
Flame Brush ◽  
Lean Conditions

Hydrogenated premixed methane/air flames under lean conditions are simulated in this study. The computational model of the high pressure chamber setup of Orleans - ICARE (France) has been developed. The k-ε turbulence model with Pope-correction is used for turbulence modeling. The laminar flame properties are computed using GRI-Mech 3.0 mechanism with Chemkin software package. The turbulent flame front statistics are investigated with three premixed combustion models, namely Zimont, Coherent Flame Model (CFM) and modified version of CFM model (MCFM) models. It has been observed that increasing the volumetric percentage of hydrogen in the mixture results in reducing the flame-end position. The flame brush thickness becomes thinner as well. Satisfactory results have been obtained compared to experiments.

Prosodic Impairment Associated With Traumatic Brain Injury

2009 ◽  
Vol 19 (3) ◽  
pp. 97-102
Author(s):  
Billy Irwin
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Detailed Analysis ◽  
Acoustic Characteristics ◽  
Individual Variations

Abstract Purpose: This article discusses impaired prosody production subsequent to traumatic brain injury (TBI). Prosody may affect naturalness and intelligibility of speech significantly, often for the long term, and TBI may result in a variety of impairments. Method: Intonation, rate, and stress production are discussed in terms of the perceptual, physiological, and acoustic characteristics associated with TBI. Results and Conclusions: All aspects of prosodic production are susceptible to the effects of damage resulting from TBI. There are commonly associated prosodic impairments; however, individual variations in specific aspects of prosody require detailed analysis.

Age-Related Decline in Emotional Prosody Discrimination

2014 ◽  
Vol 61 (3) ◽  
pp. 215-223 ◽  
Author(s):  
Rachel L. C. Mitchell ◽  
Rachel A. Kingston
Keyword(s):  
Older Adults ◽  
Auditory Perception ◽  
Duration Discrimination ◽  
Pitch Perception ◽  
Sensory Level ◽  
Emotional Prosody ◽  
Processing Stage ◽  
Acoustic Characteristics ◽  
Age Related ◽  
Level Of Processing

It is now accepted that older adults have difficulty recognizing prosodic emotion cues, but it is not clear at what processing stage this ability breaks down. We manipulated the acoustic characteristics of tones in pitch, amplitude, and duration discrimination tasks to assess whether impaired basic auditory perception coexisted with our previously demonstrated age-related prosodic emotion perception impairment. It was found that pitch perception was particularly impaired in older adults, and that it displayed the strongest correlation with prosodic emotion discrimination. We conclude that an important cause of age-related impairment in prosodic emotion comprehension exists at the fundamental sensory level of processing.

AN EULERIAN-LAGRANGIAN SPRAY AND ATOMIZATION MODEL WITH IMPROVED TURBULENCE MODELING

2009 ◽  
Vol 19 (8) ◽  
pp. 727-739 ◽  
Author(s):  
Wei Ning ◽  
Rolf D. Reitz ◽  
Ramachandra Diwakar ◽  
Andreas M. Lippert
Keyword(s):  
Turbulence Modeling
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