Effect of Velocity Ratio on Noise Source Distribution of Coaxial Jets

AIAA Journal ◽  
2010 ◽  
Vol 48 (7) ◽  
pp. 1504-1512 ◽  
Author(s):  
Dimitri Papamoschou ◽  
Sara Rostamimonjezi
Keyword(s):  
Noise Source ◽  
Velocity Ratio ◽  
Source Distribution ◽  
Coaxial Jets

Noise Reduction of Blade-Passing Frequency Components in a Centrifugal Blower

2004 ◽  
Author(s):  
Yutaka Ohta ◽  
Eisuke Outa
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Source ◽  
Higher Order ◽  
Pressure Level ◽  
Source Distribution ◽  
Centrifugal Blower ◽  
Blade Passing Frequency ◽  
Active Cancellation ◽  
Frequency Components

A hybrid-type noise control method is applied to fundamental and higher-order blade-passing frequency components, abbreviated to BPF components, radiated from a centrifugal blower. An active cancellation of the BPF noise source is conducted based on a detailed investigation of the noise source distribution by using correlation analysis. The sound pressure level of 2nd- and/or 3rd-order BPF can be reduced by more than 15 decibels and discrete tones almost eliminate from the power spectra of blower-radiated noise. On the other hand, the sound pressure level of the fundamental BPF is difficult to reduce effectively by the active cancellation method because of the large amplitude of the noise source fluctuation. However, the fundamental BPF is largely influenced by the frequency-response characteristics of the noise transmission passage, and is passively reduced by appropriate adjusting of the inlet duct length. Simultaneous reduction of BPF noise, therefore, can be easily made possible by applying passive and active control methods on the fundamental and higher-order BPF noise, respectively. We also discuss the distribution pattern of BPF noise sources by numerical simulation of flow fields around the scroll cutoff.

Comparisons of Initially Turbulent, Low-Velocity-Ratio Circular and Square Coaxial Jets

AIAA Journal ◽  
2003 ◽  
Vol 41 (2) ◽  
pp. 230-239 ◽  
Author(s):  
Dimitris E. Nikitopoulos ◽  
Jason W. Bitting ◽  
Sivaram Gogineni
Keyword(s):  
Velocity Ratio ◽  
Low Velocity ◽  
Coaxial Jets

Jet Noise Source Distribution from Far-Field Cross Correlations

AIAA Journal ◽  
1977 ◽  
Vol 15 (6) ◽  
pp. 771-772 ◽  
Author(s):  
L. Maestrello ◽  
Chen-Huei Liu
Keyword(s):  
Noise Source ◽  
Jet Noise ◽  
Source Distribution ◽  
Far Field ◽  
Cross Correlations

Effects of Jet Noise Source Distribution on Acoustic Far-Field Measurements

2012 ◽  
Vol 11 (7-8) ◽  
pp. 885-915 ◽  
Author(s):  
Ching-Wen Kuo ◽  
Jérémy Veltin ◽  
Dennis K. McLaughlin
Keyword(s):  
Noise Source ◽  
Jet Noise ◽  
Field Measurements ◽  
Source Distribution ◽  
Far Field

Flow Characteristics of Swirling Coaxial Jets From Divergent Nozzles

1987 ◽  
Vol 109 (3) ◽  
pp. 275-282 ◽  
Author(s):  
T. Mahmud ◽  
J. S. Truelove ◽  
T. F. Wall
Keyword(s):  
Bituminous Coal ◽  
Static Pressure ◽  
Reverse Flow ◽  
Velocity Ratio ◽  
Flow Characteristics ◽  
Aerodynamic Characteristics ◽  
Flow Zone ◽  
Mean Velocity ◽  
Coaxial Jets ◽  
Mass Flowrate

The aerodynamic characteristics of free, swirling, coaxial jets issuing from an air model of a typical burner for pulverized bituminous coal have been studied. Detailed measurements of mean velocity and static pressure have been obtained in the region near the nozzle exit. The boundary of the reverse-flow zone has been mapped and the recirculated-mass flowrate measured in order to quantify the effects of velocity ratio and swirl in the primary and secondary jets. The influence of burner geometry (divergent-nozzle length and centre-line blockage) has also been studied. The type of flow pattern is found to depend upon the level of swirl in the primary and secondary jets. The recirculated-mass flowrate is predominantly influenced by secondary swirl. The measurements have been compared with predictions obtained by numerical solution of the governing conservation equations in orthogonal curvilinear co-ordinates. The general features of the flows are adequately predicted although discrepancies in detail seem to indicate deficiencies in the turbulence model.

Incorporating spatial gradient observations into seismic noise interferometry

2021 ◽  
Author(s):  
Patrick Paitz ◽  
Korbinian Sager ◽  
Christian Boehm ◽  
Andreas Fichtner
Keyword(s):  
Noise Source ◽  
Source Distribution ◽  
Seismic Interferometry ◽  
Spatial Gradient ◽  
Source Inversion ◽  
Common Assumption ◽  
Wide Range ◽  
The Common ◽  
Arbitrary Noise ◽  
Public Datasets

<p>With an increasing availability of next-generation instruments in seismology such as Distributed Acoustic Sensing (DAS) interrogators and rotation sensors, as well as public datasets from these instruments, there is a demand for incorporating these new gradient observables into the workflows of seismic interferometry and noise source inversion.</p><p>Dropping the common assumption of Green’s function retrieval, we derive a generalized formulation for seismic interferometry that can utilize not only displacement measurements but also spatial and temporal gradients thereof – including velocity, strain and rotation.</p><p>Based on this formulation, we are able to simulate interferometric wavefields of displacement and gradient observations or arbitrary combinations of these observables, for heterogeneous visco-elastic media, and for arbitrary noise source distributions.</p><p>We demonstrate how to derive adjoint-based expressions for finite-frequency sensitivity kernels of the interferometric wavefields with respect to subsurface structure and noise source distributions, for a wide range of observed quantitates and combinations thereof. We provide numerical examples of such sensitivity kernels.</p><p>Especially in environments where the common assumption of a homogeneous noise source distribution is violated, our formulation enables correlation-wavefield based inversions, combining different seismic observables.</p><p>The discussed theoretical and numerical developments bring us one step closer to multi-observational full waveform ambient noise inversion, underlining the potential and possible impact of recent developments in seismic instrumentation to seismology across all scales.</p>

Heterogeneous cloud-supercomputing framework for daily seismic noise source inversion

2020 ◽  
Author(s):  
Alexey Gokhberg ◽  
Laura Ermert ◽  
Jonas Igel ◽  
Andreas Fichtner
Keyword(s):  
Real Time ◽  
Seismic Noise ◽  
Cross Correlation ◽  
Noise Source ◽  
Workflow Management ◽  
Source Distribution ◽  
Ambient Seismic Noise ◽  
Source Inversion ◽  
Finite Frequency ◽  
Noise Sources

<p>The study of ambient seismic noise sources and their time- and space-dependent distribution is becoming a crucial component of the real-time monitoring of various geosystems, including active fault zones and volcanoes, as well as geothermal and hydrocarbon reservoirs. In this context, we have previously implemented a combined cloud - HPC infrastructure for production of ambient source maps with high temporal resolution. It covers the entire European continent and the North Atlantic, and is based on seismic data provided by the ORFEUS infrastructure. The solution is based on the Application-as-a-Service concept and includes (1) acquisition of data from distributed ORFEUS data archives, (2) noise source mapping, (3) workflow management, and (4) front-end Web interface to end users.</p><p>We present the new results of this ongoing project conducted with support of the Swiss National Supercomputing Centre (CSCS). Our recent goal has been transitioning from mapping the seismic noise sources towards modeling them based on our new method for near real-time finite-frequency ambient seismic noise source inversion. To invert for the power spectral density of the noise source distribution of the secondary microseisms we efficiently forward model global cross-correlation wavefields for any noise distribution. Subsequently, a gradient-based iterative inversion method employing finite-frequency sensitivity kernels is implemented to reduce the misfit between synthetic and observed cross correlations.</p><p>During this research we encountered substantial challenges related to the large data volumes and high computational complexity of involved algorithms. We handle these problems by using the CSCS massively parallel heterogeneous supercomputer "Piz Daint". We also apply various specialized numeric techniques which include: (1) using precomputed Green's functions databases generated offline with Axisem and efficiently extracted with Instaseis package and (2) our previously developed high performance package for massive cross correlation of seismograms using GPU accelerators. Furthermore, due to the inherent restrictions of supercomputers, some crucial components of the processing pipeline including the data acquisition and workflow management are deployed on the OpenStack cloud environment. The resulting solution combines the specific advantages of the supercomputer and cloud platforms thus providing a viable distributed platform for the large-scale modeling of seismic noise sources.</p>

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