scholarly journals EXPERIMENTAL INVESTIGATION OF ACOUSTIC FIELD INFLUENCE FOR AEROSOLS PARTICLES / AKUSTINIO LAUKO ĮTAKOS AEROZOLIO DALELIŲ KOAGULIACIJAI EKSPERIMENTINIAI TYRIMAI

2016 ◽  
Vol 7 (6) ◽  
pp. 609-612
Author(s):  
Ina Tetsman ◽  
Irina Grinbergienė
Keyword(s):  
Experimental Investigation ◽  
Acoustic Field ◽  
Sound Pressure ◽  
Particle Diameter ◽  
Particle Coagulation ◽  
Experimental Stand ◽  
Coagulation Of Particles ◽  
Field Excitation ◽  
Field Sound ◽  
Field Influence

There were made tests of particulate matter (aerosol), of coagula-tion efficiency, depending on the acoustic field sound pressure and frequency. It is described experimental stand that is used to do researches and methodology of experiments performance. It is used two sound generators for acoustic field excitation: piezoe-lectric and aero-acoustic. It was determined after researches, that increasing the frequency of the acoustic field, it is increased rate of particle coagulation when particle diameter not greater than 1 μm. Effectively coagulation of particles up to 1 μm in diameter must subsonic acoustic field frequencies, as the particles over 1 μm in diameter must be lower than the frequency of ultrasonic acoustic field. Atlikti labai mažo skersmens kietųjų dalelių koaguliacijos efektyvumo, priklausomai nuo akustinio lauko garso slėgio ir dažnio, tyrimai. Aprašytas tyrimams atlikti naudotas eksperimentinis stendas ir eksperimentų atlikimo metodika. Akustiniam laukui žadinti naudoti du garso generatoriai: pjezoelektrinis ir aeroakustinis. Atlikus tyrimus nustatyta, kad, didėjant akustinio poveikio dažniui, dalelių koaguliacijos greitis didėja, kai dalelių skersmuo neviršija 1 μm. Efektyviausiai dalelių iki 1 μm skersmens koaguliacijai reikia ultragarsinių dažnių, didesnio nei 1 μm skersmens dalelėms reikia žemesnio dažnio už ultragarsinį.

Laboratory and in situ sound absorption measurement under a synthetized diffuse acoustic field

2019 ◽  
Vol 26 (4) ◽  
pp. 223-242
Author(s):  
Olivier Robin ◽  
Alain Berry ◽  
Celse Kafui Amédin ◽  
Noureddine Atalla ◽  
Olivier Doutres ◽  
...  
Keyword(s):  
Acoustic Field ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Field ◽  
Geometrical Parameters ◽  
In Situ Conditions ◽  
Field Excitation ◽  
Acoustic Environments ◽  
Field Sound

This article reports numerical and experimental results concerning the estimation of the diffuse field sound absorption coefficient of several different materials under a synthetized diffuse acoustic field excitation in laboratory and in situ conditions. The proposed measurement method is based on a sound field reproduction approach and a synthetic array of acoustic monopoles facing the material to be tested. Numerical simulations are first conducted to optimize the geometrical parameters of the method and to compute theoretical sound absorption coefficients of the considered materials. Measurements on a set of six typical acoustic materials are then conducted following the standardized reverberant room method as well as the proposed approach in a hemi-anechoic room and in two realistic rooms. Albeit showing limitations in the low-frequency domain, the proposed method enables a significant reduction of the tested specimen dimensions compared with the reverberant room method and allows performing tests in non-ideal acoustic environments.

scholarly journals The Limits of Fine Particle Ultrasonic Coagulation

Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1607
Author(s):  
Vladimir N. Khmelev ◽  
Viktor A. Nesterov ◽  
Alexander S. Bochenkov ◽  
Andrey V. Shalunov
Keyword(s):  
Sound Pressure Level ◽  
Fine Particle ◽  
Sound Pressure ◽  
Pressure Level ◽  
Swirling Flows ◽  
Particle Coagulation ◽  
Suggested Approach ◽  
Acoustic Flows ◽  
Coagulation Of Particles ◽  
Reflecting Surfaces

This paper describes the studies conducted in order to identify the limits of ultrasonic exposure’s effect on the fine particle coagulation process. It has been established as a result of the studies that ultrasonic exposure with a sound pressure level of 160 dB is capable of ensuring coagulation of particles sized 2.5 µm with efficiency δ = 83%. An increase of the coagulation up to 13% is induced with generation of swirling flows. The suggested approach to increasing the coagulation efficiency owing to vortex-type flows between the radiating and reflecting surfaces ensures efficiency of coagulation δ = 96 %. The implementation of this approach has shown that with generation of vortex-type acoustic flows, it makes the most sense for a concentration of particles of 18×10−3 g/m3. Incremental efficiency at such concentrations amounts to 50%.

Hydrodynamic Noise and Radiated Mechanism of 3D Cavity

2012 ◽  
Vol 217-219 ◽  
pp. 2590-2593 ◽  
Author(s):  
Yu Wang ◽  
Bai Zhou Li
Keyword(s):  
Sound Pressure ◽  
Near Field ◽  
Low Frequency ◽  
Dipole Source ◽  
Fluctuating Pressure ◽  
Common Structure ◽  
Hydrodynamic Noise ◽  
Near Field Sound ◽  
Equivalent Sources ◽  
Field Sound

The flow past 3D rigid cavity is a common structure on the surface of the underwater vehicle. The hydrodynamic noise generated by the structure has attracted considerable attention in recent years. Based on LES-Lighthill equivalent sources method, a 3D cavity is analyzed in this paper, when the Mach number is 0.0048. The hydrodynamic noise and the radiated mechanism of 3D cavity are investigated from the correlation between fluctuating pressure and frequency, the near-field sound pressure intensity, and the propagation directivity. It is found that the hydrodynamic noise is supported by the low frequency range, and fluctuating pressure of the trailing-edge is the largest, which is the main dipole source.

scholarly journals Structure-Acoustic Coupling Analysis of Vibration and Underwater Acoustic Radiation of a Ring-Stiffened Conical Shell

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qingtao Gong ◽  
Zhanyang Chen ◽  
Hongbin Gui ◽  
Dong Yu
Keyword(s):  
Acoustic Field ◽  
Conical Shell ◽  
Sound Pressure ◽  
Field Model ◽  
Acoustic Radiation ◽  
Rear Side ◽  
The Finite Element Method ◽  
Underwater Acoustic ◽  
Acoustic Coupling ◽  
Element Method

The underwater acoustic radiation of the submarine power cabin has recently become a hot topic in the industry and also in the academia. In this article, the vibration and underwater acoustic radiation of a ring-stiffened conical shell with bases are investigated numerically by means of the combination of the finite element method and boundary element method. The acoustic radiation field is obtained by the traditional acoustic field model and ISO acoustic field model, respectively. A series of numerical examples are given, and the results are compared. Besides, the sound pressure at different positions with frequency is further studied. It is shown that the sound radiated by the structure mainly propagates to the side directions of the shell and propagates relatively less to the front side and the rear side.

scholarly journals A System for Acoustic Field Measurement Employing Cartesian Robot

2016 ◽  
Vol 23 (3) ◽  
pp. 333-343 ◽  
Author(s):  
Maciej Szczodrak ◽  
Adam Kurowski ◽  
Józef Kotus ◽  
Andrzej Czyżewski ◽  
Bożena Kostek
Keyword(s):  
Acoustic Field ◽  
Energy Flow ◽  
Velocity Vector ◽  
Sound Pressure ◽  
Sound Field ◽  
Acoustic Energy ◽  
The Other ◽  
Object Shape ◽  
Movement Path ◽  
Optimum Path

AbstractA system setup for measurements of acoustic field, together with the results of 3D visualisations of acoustic energy flow are presented in the paper. Spatial sampling of the field is performed by a Cartesian robot. Automatization of the measurement process is achieved with the use of a specialized control system. The method is based on measuring the sound pressure (scalar) and particle velocity(vector) quantities. The aim of the system is to collect data with a high precision and repeatability. The system is employed for measurements of acoustic energy flow in the proximity of an artificial head in an anechoic chamber. In the measurement setup an algorithm for generation of the probe movement path is included. The algorithm finds the optimum path of the robot movement, taking into account a given 3D object shape present in the measurement space. The results are presented for two cases, first without any obstacle and the other - with an artificial head in the sound field.

Experimental Investigation of Convective Melting of Granular Packed Bed Under Microgravity

2000 ◽  
Author(s):  
J. Jiang ◽  
Y. Hao ◽  
Y.-X. Tao
Keyword(s):  
Experimental Investigation ◽  
Average Particle Size ◽  
Particle Diameter ◽  
Vertical Direction ◽  
Packed Bed ◽  
Melting Rate ◽  
Control Flow ◽  
Solid Particles ◽  
Average Particle ◽  
Ice Particles

Abstract To improve the understanding of convective melting of packed solid particles in a fluid, an experimental investigation is conducted to study the melting characteristics of a packed bed by unmasking the buoyancy forces due to the density difference between the melt and solid particles. A close-loop apparatus, named the particle-melting-in-flow (PMF) module, is designed to allow a steady state liquid flow under a specified temperature. The module is on board NASA’s KC-135 reduced gravity aircraft for the experiments. In the test module, water is used as the fluid, and ice particles are fed to the test section at the beginning of the test. As the liquid flows though the bed, the solid grains melt. A perforate plate, through which liquid can flow while the ice particles are retained, bounds the downstream of the packed bed. From the digital video images the local packed bed thickness is measured under control flow rate, and the melting rate is determined. The temperature distribution along the horizontal direction and vertical direction is measured using 19 thermocouples. An infrared camera is mounted to record the local temperature variation between liquid and solid. The melting rates are presented as a function of upstream flow velocity, temperature and initial average particle size of the packed bed. It is found that the melting rate is influenced mainly by the ratio of the Reynolds number (Re, based on the initial particle diameter) to the square of the Froud number (Fr), and me Stefan number (Ste). In general, the dimensionless melting rate decreases as Re/Fr2 increases and increases as Ste increases. With the absence of gravity, i.e., Froud number approaches infinity, a maximum melting rate can be achieved for otherwise the same test conditions. The increase in the melting rate with the increase in Stephan number also becomes more pronounced under the zero gravity condition.

Effects of Quay Wall and Seabed Reflection on the AUV Acoustic Radiation Test Analysis

2014 ◽  
Vol 599-601 ◽  
pp. 922-926
Author(s):  
Guo Liang Xu ◽  
Qi Wei He ◽  
Shao Chun Ding ◽  
Hai Bo Wan
Keyword(s):  
Acoustic Field ◽  
Field Test ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Near Field ◽  
Test Analysis ◽  
Complex Sound ◽  
Quay Wall ◽  
Radiation Test ◽  
Acoustical Holography

To analyze effects of quay environment on the AUV radiated acoustic field test, the PNAH (PNAH: planar near-field acoustical holography) was used to simulate acoustic field. By simulating the free and non-free acoustic field and comparing amplitudes and angles of complex sound pressure, Analyze effects of quay wall and seabed reflection on the AUV radiated acoustic field test to determine the standard of quay wall and seabed environment which meets testing. The work would provide a certain reference for the AUV radiated acoustic field test.

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