Acoustic Radiation Computation from an Engine Inlet with Aerodynamic Flow Field

2004 ◽  
Author(s):  
Simon Richards ◽  
XiaoXian Chen ◽  
Xin Zhang
Keyword(s):  
Flow Field ◽  
Acoustic Radiation

Unsteady Flow Field and Noise Generation in a Centrifugal Pump Impeller With a Vaneless Diffuser

2005 ◽  
Author(s):  
Giorgio Pavesi ◽  
Guido Ardizzon ◽  
Giovanna Cavazzini
Keyword(s):  
Flow Field ◽  
Acoustic Radiation ◽  
Wake Flow ◽  
Test Model ◽  
Centrifugal Pumps ◽  
Vaneless Diffuser ◽  
Pump Impeller ◽  
Model Flow ◽  
Return Channel ◽  
The Impact

To improve understanding of the phenomena of stall in centrifugal pumps, extensive research was conducted to investigate the impact on flow field instabilities and the noise generated in a pump equipped with a diffuser. A pump fitted with a vaneless diffuser and a return channel was used as the test model. Flow velocity was measured at the pump and at diffuser inflow to establish a link between the flow field structure and acoustic radiation. Activity was based upon the cross spectral analysis of output signals from piezoelectric transducers placed flush with the wall at the inflow and outflow of the pump, and 3D fully-viscous unsteady computations. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage and destabilised jet-wake flow in the passage. Consequently, periodic fluctuations were seen at impeller discharge which were found to be coherent from blade to blade and possessed a rich harmonic content. With the exception of the total pressure in the far field, the pressure frequency scattering by the pump was found to be consistent when compared to the experimental and analytic results.

Effect of an excrescence in the slat cove: Flow-field, acoustic radiation and coherent structures

2015 ◽  
Vol 44 ◽  
pp. 108-115 ◽  
Author(s):  
D.S. Souza ◽  
D. Rodríguez ◽  
L.G.C. Simões ◽  
M.A.F. Medeiros
Keyword(s):  
Flow Field ◽  
Coherent Structures ◽  
Acoustic Radiation

Numerical and Experimental Investigations on a Centrifugal Pump With and Without a Vaned Diffuser

2004 ◽  
Author(s):  
G. Pavesi ◽  
G. Ardizzon ◽  
G. Cavazzini
Keyword(s):  
Flow Field ◽  
Acoustic Radiation ◽  
Pressure Sensors ◽  
Wake Flow ◽  
Experimental Investigations ◽  
Test Model ◽  
Centrifugal Pumps ◽  
Vaned Diffuser ◽  
Return Channel ◽  
The Impact

Extensive research on centrifugal pumps was designed to investigate the impact of a diffuser on flow field instabilities and the noise generated by these instabilities. Activity was based upon a coupled use of measurements and 3D fully-viscous, unsteady computations. The test model was a seven-blade pump-turbine, used as a pump. Fitted with a vaneless diffuser, and two vaned diffusers with twenty-two adjustable, guide-diffuser vanes, and a return channel with eleven continuous vanes. Diffusers were equipped with eight pressure sensors in the adjustable guide-diffuser vanes, and nineteen pressure taps in the continuous vanes. To establish a link between the flow field structure and acoustic radiation, flow velocity was measured in the vaneless part of the diffuser. Piezoelectric transducers, placed flush with the wall, were used to measure pressure fluctuation inside the blade channels. Signal analysis was carried out in the frequency domain. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage, and destabilized jet-wake flow in the passage. This instability caused a periodic fluctuation at the discharge of the impeller. Fluctuations were found to be coherent from blade to blade, and to possess a rich harmonic content. Numerical analyses did not fully confirm these results.

Research of Whirlpool Sound Radiation in Turbulence Coherent Structures

2013 ◽  
Author(s):  
Xiaosa Li ◽  
Zegang Qian ◽  
Qichao Yang
Keyword(s):  
Flow Field ◽  
Vortex Shedding ◽  
Coherent Structures ◽  
Acoustic Radiation ◽  
Unit Length ◽  
Vortex Pair ◽  
Aerodynamic Noise ◽  
Large Eddy Simulation Model ◽  
Noise Radiation ◽  
Eddy Simulation

The compressor aerodynamic noise consists of suction, exhausting noise, gas power noise and so on, and the exhausting noise is dominating. Gas which is compressed released instantaneously to form vortex injection noise and exhausting pulsation noise, yet will cause pipe vibration. Large Eddy Simulation model in fluid software FLUENT have been adopted to analyze unsteady flow field and the acoustic field and research unsteady vortex shedding and its noise radiation characteristics in compressor pipes. The results show that: the trailing edge vortex shedding phenomenon, interaction between separation vortex and the trailing vortex of downstream lead to a large gas pulsation which makes noise radiation enhanced in the compressor pipe flow field in screw compressor exhausting orifice. Combination turbulence and vortex-pair phenomena in coherent structures, based on the vortex sound equation, a mathematical model of vortex-pair acoustic radiation is established. Finally unit length sound power of the whirlpool is draw to lρ0U3M4.

A summary of acoustic characteristics and control techniques of underwater non-cavitation thruster

2019 ◽  
Vol 233 (18) ◽  
pp. 6339-6356
Author(s):  
Ma Cheng
Keyword(s):  
Flow Field ◽  
Sound Production ◽  
Acoustic Radiation ◽  
Great Influence ◽  
Low Frequency ◽  
Open Water ◽  
Low Noise ◽  
Acoustic Characteristics ◽  
Broadband Spectrum ◽  
Open Water Performance

This paper gives a detailed description of the mechanism of sound production, acoustic characteristics and prediction methods for radiation sound spectrums (low frequency line spectrum, low frequency broadband spectrum and high frequency broadband spectrum) of non-cavitation thruster and the secondary acoustic radiation caused by the unsteady force which excited both shaft system and hull in the unsteady flow field. It indicates that the underwater thruster has a great influence on underwater noise of the navigation body with its direct or secondary radiation sound. The paper also describes two control methods, one is mostly used to control the uniformity of the flow field, while the other is used to design low-noise thruster such as pump-jet thruster and highly skewed propeller. Additionally, a new type multi-blade coupling propeller with unique features is proposed to achieve further noise reduction and open water performance improvement.

Rationale Abklärung von Lebererkrankungen

2017 ◽  
Vol 74 (3) ◽  
pp. 79-86
Author(s):  
Leona von Köckritz ◽  
Andrea De Gottardi
Keyword(s):  
Acoustic Radiation ◽  
Radiation Force ◽  
Acoustic Radiation Force ◽  
Acoustic Radiation Force Impulse ◽  
Alkalische Phosphatase ◽  
Gamma Glutamyltransferase ◽  
Alpha 1 Antitrypsin

Zusammenfassung. Im klinischen Alltag werden häufig erhöhte Leberwerte beobachtet. In der Regel erfordern sie weitere Abklärungen bezüglich der möglichen Ätiologie und des Schweregrad einer akuten oder chronischen Lebererkrankung. Die Abklärung sollte dabei neben einer gezielten Anamnese und sorgfältigen klinischen Untersuchung, auch die Bestimmung von laborchemischen Markern für Cholestase und Leberfunktionsstörungen (wie Alkalische Phosphatase, gamma-Glutamyltransferase, Bilirubin, Albumin und Gerinnungsfaktoren) umfassen. Die Bestimmung weiterer Parameter wie Ferritin und Transferrinsättigung, Autoimmunantikörper, Virusserologien, alpha-1 Antitrypsin und Coerulolasmin können weitere Hinweise für die kausalen Zusammenhänge der Leberfunktionsstörung liefern. Bei Patienten mit Lebererkrankungen ist eine sonografische Beurteilung der Leber obligat. Ergänzend zur Sonografie werden heute weitere nicht-invasive Methoden wie Fibroscan, Acoustic Radiation Force Impulse Elastometrie und Magnet-Resonanz-Elastografie zur Beurteilung der Leberfibrose eingesetzt. In ausgewählten Fällen ist eine Leberbiopsie notwendig, um den Grad der Fibrose und die Ätiologie der Lebererkrankung zu eruieren. Mithilfe eines Fallbeispiels, diskutieren die Autoren im Folgenden die rationale Anwendung diagnostischer Tests und deren korrekte Interpretation und schlagen eine Orientierungshilfe zur rationalen Abklärung von Patienten mit Lebererkrankungen vor.

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