Resonance-enhanced compact nonlinear acoustic source of low frequency collimated beam for imaging applications in highly attenuating media

2016 ◽  
Vol 140 (4) ◽  
pp. 3204-3204
Author(s):  
Cristian Pantea ◽  
Dipen N. Sinha
Keyword(s):  
Low Frequency ◽  
Acoustic Source ◽  
Nonlinear Acoustic ◽  
Collimated Beam

scholarly journals Acoustic Source Data for Medium Speed IC-Engines

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Antti Hynninen ◽  
Raimo Turunen ◽  
Mats Åbom ◽  
Hans Bodén
Keyword(s):  
High Frequency ◽  
Internal Combustion Engines ◽  
Low Frequency ◽  
Acoustic Source ◽  
Ic Engine ◽  
Source Characteristics ◽  
Medium Speed ◽  
Source Data ◽  
Exhaust Noise ◽  
Ic Engines

Knowledge of the acoustic source characteristics of internal combustion engines (IC-engines) is of great importance when designing the exhaust duct system and its components to withstand the resulting dynamic loads and to reduce the exhaust noise emission. The goal of the present study is to numerically and experimentally investigate the medium speed IC-engine acoustic source characteristics, not only in the plane wave range but also in the high frequency range. The low frequency acoustic source characteristics were predicted by simulating the acoustic multiload measurements by using a one-dimensional process simulation code. The low frequency in-duct exhaust noise of a medium speed IC-engine can be quite accurately predicted. The high frequency source data is estimated by averaging the measured acoustic pressures with different methods; using the simple cross-spectra averaging method seems promising in this instance.

Numerical Simulation of the Buried Object Detection Based on Underwater Plasma Acoustic Source

2011 ◽  
Vol 105-107 ◽  
pp. 80-83
Author(s):  
Jun Zhang ◽  
Xin Wu Zeng ◽  
Yi Bo Wang ◽  
Zhen Fu Zhang ◽  
Dan Chen
Keyword(s):  
Wave Propagation ◽  
Object Detection ◽  
Pulse Length ◽  
Low Frequency ◽  
Basic Mechanism ◽  
Propagation Model ◽  
Staggered Grid ◽  
Acoustic Source ◽  
Buried Objects ◽  
Buried Object

Detection and classification of buried objects is of great importance in underwater counterterrorism and archaeology. To penetrate the sediment, a low frequency intensive acoustic source is needed. Underwater plasma acoustic source (UPAS) with high voltage discharge has the advantage of adjustable pulse length, high source level output and no pollution to the environment, which can satisfy these needs. In this paper, we introduced the UPAS, including its basic mechanism, structure and pressure output. Then we build up an elastic wave propagation model, solved it with finite difference and staggered grid methods, and combined with certain source and boundary condition, we simulated and analyzed the pressure wave propagation in time domain with an aluminum cylinder buried in sediment, from the results we validated the effectiveness of UPAS in the application of buried object detection.

scholarly journals Diagnostics of concrete plate in bending with ultrasonic waves modulated by low frequency oscillations

2013 ◽  
Vol 12 (1) ◽  
pp. 243-250
Author(s):  
Błażej Meronk ◽  
Krzysztof Wilde
Keyword(s):  
Experimental Study ◽  
Low Frequency ◽  
Ultrasonic Waves ◽  
Modulation Method ◽  
Frequency Spectra ◽  
Concrete Plate ◽  
Low Frequency Oscillations ◽  
Damaged Zone ◽  
Nonlinear Acoustic ◽  
Concrete Elements

The paper presents the experimental study on the inter-modulation method for the diagnostics of concrete elements. The tests were conducted on a concrete plate subjected to ultrasonic waves and low frequency vibrations. The nonlinear acoustic effects, recorded in the experiments, made it possible to detect the presence of damaged zones. Further studies are necessary to establish the relation between the sidebanes of frequency spectra and the size of the damaged zone.

LES Predictions of Jet Noise for a Pylon-Mounted Dual Stream Nozzle and Jet Surface Interactions

2016 ◽  
Author(s):  
P. Vogel ◽  
J. Bin ◽  
N. Sinha
Keyword(s):  
Supersonic Jet ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Acoustic Source ◽  
Noise Sources ◽  
Surface Time ◽  
Acoustic Source Localization ◽  
Jet Nozzle ◽  
Field Noise

An end-to-end LES/FW-H noise prediction model has been demonstrated and validated with acoustic and flowfield data from a dual stream nozzle with pylon experiment conducted at NASA GRC using their Jet Engine Simulator (JES) geometry. Results show a large region of high turbulent kinetic energy (TKE) in the wake of the pylon. Acoustic Source Localization (ASL) studies using our numerical phased array methodology show this wake region to be the principle location of low frequency noise sources while higher frequency sources occur nearer to the nozzle lips. Numerical simulations have also been conducted on Jet-Surface Interaction (JSI) effects of a supersonic jet exhausting parallel to a finite surface. Time-averaged LES data and far-field noise predictions have been obtained for multiple surface locations as well as for an isolated jet nozzle. For upstream observers located below the surface, results show an increase in low-frequency noise over what was predicted for the isolated nozzle due to JSI effects and decrease in high-frequency noise due to shielding. This was significantly more pronounced for an over-expanded jet than for an under-expanded jet, an effect that was primarily attributed to the shorter core length of the over-expanded jet.

Analysis of Vibro-Acoustic Modulations in Nonlinear Acoustics Used for Impact Damage Detection - Numerical and Experimental Study

2013 ◽  
Vol 558 ◽  
pp. 341-348 ◽  
Author(s):  
Łukasz Pieczonka ◽  
Andrzej Klepka ◽  
Wieslaw Jerzy Staszewski ◽  
Tadeusz Uhl ◽  
Francesco Aymerich
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Composite Plate ◽  
Natural Frequencies ◽  
Impact Damage ◽  
Low Frequency ◽  
Fe Modeling ◽  
Low Frequency Vibration ◽  
Frequency Excitation ◽  
Nonlinear Acoustic

The paper investigates experimentally the effect of low-frequency vibration on nonlinear vibro-acoustic wave modulations applied to the detection of Barely Visible Impact Damage (BVID) in a composite plate. Finite Element (FE) modeling was used in a pretest stage to identify different motion scenarios of delaminated surfaces and relate them to natural frequencies of the damaged plate. In particular the opening-closing and frictional sliding actions of the defected interfaces have been considered. Subsequently, the identified frequencies have been used for low frequency excitation in nonlinear acoustic experiments on a composite plate with impact damage.

scholarly journals Ultrasonic modulated waves for diagnostics of concrete elements in bending

2014 ◽  
Vol 13 (2) ◽  
pp. 283-290
Author(s):  
Błażej Meronk ◽  
Krzysztof Wilde
Keyword(s):  
Experimental Study ◽  
Low Frequency ◽  
Ultrasonic Waves ◽  
New Method ◽  
Practical Application ◽  
Concrete Plate ◽  
Low Frequency Oscillations ◽  
Nonlinear Acoustic ◽  
Modulated Waves ◽  
Concrete Elements

The paper presents the experimental study on the diagnostics of concrete elements with the use of nonlinear acoustic effects. The tests were conducted on a concrete plate subjected to ultrasonic waves modulated with and without an additional low frequency actuator. The experimental results showed that the new method based on the direct modulation of diagnostic ultrasonic waves also provided sub-harmonic frequencies that indicated the presence of damage. The new method does not require a low frequency actuator for generation of low frequency oscillations, and therefore, is more suitable for practical application.

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