Turbomachinery Exhaust Noise Radiation Experiments - Part 2: In-Duct and Far-Field Mode Analysis

2008 ◽  
Author(s):  
Ulf Tapken ◽  
Roland Bauers ◽  
Frank Arnold ◽  
Joergen Zillmann
Keyword(s):  
Mode Analysis ◽  
Far Field ◽  
Field Mode ◽  
Noise Radiation ◽  
Exhaust Noise

Submicron Simultaneous IR and Raman Spectroscopy (IR+Raman): Breakthrough Developments in Optical Photothermal IR (O-PTIR) Combined for Enhanced Failure Analysis

2019 ◽  
Author(s):  
Jay Anderson ◽  
Mustafa Kansiz ◽  
Michael Lo ◽  
Curtis Marcott
Keyword(s):  
Raman Spectroscopy ◽  
Failure Analysis ◽  
Data Quality ◽  
Raman Spectra ◽  
Spatial Resolution ◽  
Far Field ◽  
Field Mode ◽  
Microscopic Scale ◽  
Analytical Tools ◽  
Ir And Raman

Abstract Failure analysis of organics at the microscopic scale is an increasingly important requirement, with traditional analytical tools such as FTIR and Raman microscopy, having significant limitations in either spatial resolution or data quality. We introduce here a new method of obtaining Infrared microspectroscopic information, at the submicron level in reflection (far-field) mode, called Optical-Photothermal Infrared (O-PTIR) spectroscopy, that can also generate simultaneous Raman spectra, from the same spot, at the same time and with the same spatial resolution. This novel combination of these two correlative techniques can be considered to be complimentary and confirmatory, in which the IR confirms the Raman result and vice-versa, to yield more accurate and therefore more confident organic unknowns analysis.

Mode analysis of gyrotron radiation by far field measurements

1983 ◽  
Author(s):  
Z. X. Zhang ◽  
G. Janzen ◽  
G. Muller ◽  
P. G. Schuller ◽  
M. Thumm ◽  
...  
Keyword(s):  
Field Measurements ◽  
Mode Analysis ◽  
Far Field

Transverse mode analysis of a laser beam by near- and far-field intensity measurements

1995 ◽  
Vol 34 (34) ◽  
pp. 7974 ◽  
Author(s):  
Antonello Cutolo ◽  
Tommaso Isernia ◽  
IIdegonda Izzo ◽  
Rocco Pierri ◽  
Luigi Zeni
Keyword(s):  
Laser Beam ◽  
Field Intensity ◽  
Transverse Mode ◽  
Mode Analysis ◽  
Far Field ◽  
Intensity Measurements

The analysis of near and far field pattern through mode analysis and FFT in a finite periodic dielectric gratings

2015 ◽  
Vol 17 (1) ◽  
pp. 82-90 ◽  
Author(s):  
Tae-Bong Lee ◽  
Min-Nyeon Kim
Keyword(s):  
Near Field ◽  
Bloch Wave ◽  
Wave Number ◽  
Mode Analysis ◽  
Field Pattern ◽  
Far Field ◽  
Content Type ◽  
Coupled Method ◽  
Field Patterns ◽  
Dielectric Gratings

Purpose – The purpose of this paper is to analyze far and near field emitted field patterns through more exact calculation of the modes formed in finite periodic dielectric gratings. Design/methodology/approach – For the mode calculation, equations are newly defined by applying vertical boundary condition on the assumption that transverse electric modes are generated in the structure. After finding modes, near field patterns are calculated using the wave number and coefficient of the mode. Findings – Additionally, the results from these calculations are compared with that of the rigorous-coupled method. Finally, far field patterns are derived by applying fast Fourier transform to near field patterns and also compared with the results of rigorous-coupled method. Research limitations/implications – For convenience of coordinate, we use rectangular coordinate, though the shape of radome is a hemisphere. Practical implications – In this paper, the authors derive more exact near field patterns without the assumption of infiniteness so that these results can be used practically for a making real frequency-selective structure. Originality/value – Conventional periodic finite dielectric gratings analysis has been done using Floquet–Bloch wave theory, coupled-mode, rigorous-coupled method which is based on the assumption of infiniteness of the structure.

Development of the Exhaust Systems Radiation Noise Simulation Technology

2003 ◽  
Author(s):  
Masato Sakurai ◽  
Masaki Endo ◽  
Fred Perie
Keyword(s):  
Pressure Sensors ◽  
Exhaust System ◽  
Structural Vibration ◽  
Noise Sources ◽  
Noise Radiation ◽  
Aeroacoustic Noise ◽  
Noise Simulation ◽  
Exhaust Noise ◽  
Radiation Noise ◽  
Definition Of

The purpose of this paper is to present a Finite Element method able to simulate and predict exhaust radiation noise. The simulation takes into account fluid flow pulsation, aeroacoustic noise sources; flow induced structural vibration as well as noise radiation in the far field. All those phenomena are directly calculated in a fully coupled manner. By applying measured values at the model inflow, accurate radiation noise from the exhaust system is obtained. Locations of noise sources as well as mechanisms of noise generation are clarified. The method enables the investigation of exhaust noise radiation at early development stages. The use of semiconductor pressure sensors with 1-MHz sampling as well as Laser Doppler Velocimetry contributed greatly to the measurement accuracy required for the definition of inflow conditions.

In‐Flight Far‐Field Measurement of Helicopter Impulsive Noise

1976 ◽  
Vol 21 (4) ◽  
pp. 2-16
Author(s):  
F. H. Schmitz ◽  
D. A. Boxwell
Keyword(s):  
High Speed ◽  
Impulsive Noise ◽  
Operating Conditions ◽  
Tape Recording ◽  
Far Field ◽  
Recording Equipment ◽  
Radiation Characteristics ◽  
Acoustic Data ◽  
Noise Radiation ◽  
The Subject

A new and highly successful method of collecting far‐field acoustic data radiated by helicopters in forward flight has been developed, utilizing a quiet aircraft flying in formation ahead of the subject helicopter. The lead aircraft, flown as an acoustic probe, was equipped with tape‐recording equipment and an external microphone. Spatial orientation of the helicopter with respect to the monitoring aircraft was achieved through visual flight reference. Far‐field acoustic data defining the impulsive noise radiation characteristics of the UH‐1H helicopter during high‐speed flight and partial ‐power descents have been gathered with this technique. Three distinct types of impulsive waveforms have been identified and correlated with helicopter steady operating conditions.

Noise Characteristics of Automobile Cooling Fan Based on Circumferential Mode Analysis

2021 ◽  
Author(s):  
Pengfei Chai ◽  
Zonghan Sun ◽  
Zhiqiang Chang ◽  
Zhigang Peng ◽  
Jie Tian ◽  
...  
Keyword(s):  
Automobile Industry ◽  
Cooling System ◽  
Tip Clearance ◽  
Mode Analysis ◽  
Far Field ◽  
Axial Fan ◽  
Fan Noise ◽  
Cooling Fan ◽  
Noise Characteristics ◽  
Cooling Fans

Abstract The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.

Noise Characteristics of Automobile Cooling Fan Based On Circumferential Mode Analysis

2021 ◽  
Author(s):  
Pengfei Chai ◽  
Zonghan Sun ◽  
Zhiqiang Chang ◽  
Zhigang Peng ◽  
Jie Tian ◽  
...  
Keyword(s):  
Automobile Industry ◽  
Cooling System ◽  
Tip Clearance ◽  
Mode Analysis ◽  
Far Field ◽  
Axial Fan ◽  
Fan Noise ◽  
Cooling Fan ◽  
Noise Characteristics ◽  
Cooling Fans

Abstract The fan is the main component of the cooling system of an automobile engine. A typical automobile cooling fan consists of a shrouded axial fan, stator vanes, a deflector, and a cover. With recent developments in the automobile industry, the increase in the speed of rotation and blade load of cooling fans has increased the noise generated by them. To reduce it, it is important to analyze the characteristics of this noise. This paper uses an acoustic test to examine the characteristics of flow and noise of automobile cooling fans. The frequency spectrum and far-field radiation of the noise of the fan are first analyzed through far-field measurements, and the influence of the single rotor, tip clearance of the blade, and cover on fan noise is studied. The distribution of the mode spectrum and characteristics of sound propagation of discrete tonal noise are then examined using the circumferential mode test. The influence of the flow structure on fan noise is also studied. The flow characteristics and distribution of the source of noise of the automobile cooling fan are then used to analyze the influence of the structure of the fan on the noise generated by it. The results can help develop designs to reduce the noise of automobile cooling fans.

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