Numerical Investigation of the Mean Flow Effect on the Acoustic Reflection at the Open End of Clarinet-Like Instruments

2010 ◽  
Vol 96 (5) ◽  
pp. 959-966 ◽  
Author(s):  
Andrey Ricardo da Silva ◽  
Gary P. Scavone ◽  
Arcanjo Lenzi
Keyword(s):  
Numerical Investigation ◽  
Mean Flow ◽  
Flow Effect ◽  
Acoustic Reflection ◽  
The Mean

Experimental Investigation of the Acoustic Reflection Coefficient of a Modeled Gas Turbine Impingement Cooling Section

2012 ◽  
Author(s):  
Christoph Jörg ◽  
Michael Wagner ◽  
Thomas Sattelmayer
Keyword(s):  
Reflection Coefficient ◽  
Flow Velocity ◽  
Gas Turbines ◽  
Acoustic Energy ◽  
Quality Data ◽  
Mean Flow ◽  
Impingement Cooling ◽  
Acoustic Reflection ◽  
The Mean ◽  
Mean Flow Velocity

The thermoacoustic stability of gas turbines depends on a balance of acoustic energy inside the engine. While the flames produce acoustic energy, other areas like the impingement cooling system contribute to damping. In this paper, we investigate the damping potential of an annular impingement sleeve geometry embedded into a realistic environment. A cold flow test rig was designed to represent real engine conditions in terms of geometry, and flow situation. High quality data was delivered by six piezoelectric dynamic pressure sensors. Experiments were carried out for different mean flow velocities through the cooling holes. The acoustic reflection coefficient of the impingement sleeve was evaluated at a downstream reference location. Further parameters investigated were the number of cooling holes, and the geometry of the chamber surrounding the impingement sleeve. Experimental results show that the determining parameter for the reflection coefficient is the mean flow velocity through the impingement holes. An increase of the mean flow velocity leads to significantly increased damping, and to low values of the reflection coefficient.

Flow Induced Aerodynamic Noise Analysis of Perforated Tube Mufflers

2012 ◽  
Vol 29 (2) ◽  
pp. 225-231 ◽  
Author(s):  
C.-N. Wang ◽  
C.-C. Tse ◽  
S.-C. Chen
Keyword(s):  
Transmission Loss ◽  
Noise Analysis ◽  
Helmholtz Resonator ◽  
Aerodynamic Noise ◽  
Mean Flow ◽  
Flow Effect ◽  
Flow Induced Noise ◽  
The Mean ◽  
Cfd Method ◽  
Perforated Tube

AbstractDespite the analysis of muffler performance for many years, most works focus mainly on reducing inlet sound and fail to consider the flow effect. Most of their results correlate well with the experimental measurements. Subsequent works have considered the mean flow effect. Owing to Doppler's effect, transmission loss curve of the muffler will shift in its corresponding frequency. However, the correlation is worse than the experimental results since the flow induced noise does not include in the analysis. This work elucidates how flow induced noise affects muffler performance by analyzing a uniform flow that passes through perforated mufflers. The flow field is calculated with the CFD method, followed by evaluation of the aerodynamic noise based on the simulation results. Additionally, the procedure is simplified by computing and comparing only the total sound power induced by the flow in the muffler interior. Two muffler types, Helmholtz resonator and plug perforated tube muffler, are analyzed and discussed.

scholarly journals Review and numerical investigation of the mean flow features of a round turbulent jet in counterflow

2020 ◽  
Vol 32 (4) ◽  
pp. 045102 ◽  
Author(s):  
Marc Rovira ◽  
Klas Engvall ◽  
Christophe Duwig
Keyword(s):  
Numerical Investigation ◽  
Turbulent Jet ◽  
Mean Flow ◽  
Flow Features ◽  
The Mean

Simple explicit model of liquid mean flow in region above axial impeller

1985 ◽  
Vol 50 (11) ◽  
pp. 2396-2410
Author(s):  
Miloslav Hošťálek ◽  
Ivan Fořt
Keyword(s):  
Vortex Flow ◽  
Flow Model ◽  
Quantitative Agreement ◽  
Mean Flow ◽  
Flat Bottom ◽  
Proposed Model ◽  
Minimum Number ◽  
The Mean ◽  
Model Equations ◽  
Radial Circulation

The study describes a method of modelling axial-radial circulation in a tank with an axial impeller and radial baffles. The proposed model is based on the analytical solution of the equation for vortex transport in the mean flow of turbulent liquid. The obtained vortex flow model is tested by the results of experiments carried out in a tank of diameter 1 m and with the bottom in the shape of truncated cone as well as by the data published for the vessel of diameter 0.29 m with flat bottom. Though the model equations are expressed in a simple form, good qualitative and even quantitative agreement of the model with reality is stated. Apart from its simplicity, the model has other advantages: minimum number of experimental data necessary for the completion of boundary conditions and integral nature of these data.

scholarly journals Technical note: Inherent benchmark or not? Comparing Nash–Sutcliffe and Kling–Gupta efficiency scores

2019 ◽  
Vol 23 (10) ◽  
pp. 4323-4331 ◽  
Author(s):  
Wouter J. M. Knoben ◽  
Jim E. Freer ◽  
Ross A. Woods
Keyword(s):  
Time Series ◽  
Coefficient Of Variation ◽  
Ad Hoc ◽  
Model Performance ◽  
Technical Note ◽  
Mean Flow ◽  
Model Adequacy ◽  
Robust Model ◽  
The Mean ◽  
Adequacy Assessment

Abstract. A traditional metric used in hydrology to summarize model performance is the Nash–Sutcliffe efficiency (NSE). Increasingly an alternative metric, the Kling–Gupta efficiency (KGE), is used instead. When NSE is used, NSE = 0 corresponds to using the mean flow as a benchmark predictor. The same reasoning is applied in various studies that use KGE as a metric: negative KGE values are viewed as bad model performance, and only positive values are seen as good model performance. Here we show that using the mean flow as a predictor does not result in KGE = 0, but instead KGE =1-√2≈-0.41. Thus, KGE values greater than −0.41 indicate that a model improves upon the mean flow benchmark – even if the model's KGE value is negative. NSE and KGE values cannot be directly compared, because their relationship is non-unique and depends in part on the coefficient of variation of the observed time series. Therefore, modellers who use the KGE metric should not let their understanding of NSE values guide them in interpreting KGE values and instead develop new understanding based on the constitutive parts of the KGE metric and the explicit use of benchmark values to compare KGE scores against. More generally, a strong case can be made for moving away from ad hoc use of aggregated efficiency metrics and towards a framework based on purpose-dependent evaluation metrics and benchmarks that allows for more robust model adequacy assessment.

scholarly journals Experimental study on the mean flow characteristics of a supersonic multiple jet configuration

2021 ◽  
Vol 108 ◽  
pp. 106377
Author(s):  
Mohammed Faheem ◽  
Aqib Khan ◽  
Rakesh Kumar ◽  
Sher Afghan Khan ◽  
Waqar Asrar ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Characteristics ◽  
Mean Flow ◽  
The Mean
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