Acoustic Power Levels Research Articles

An ultrasonically actuated fine-needle creates cavitation in bovine liver.

Ultrasonic cavitation is being used in medical applications as a way to influence matter, such as tissue or drug vehicles, on a micro-scale. Oscillating or collapsing cavitation bubbles provide transient mechanical force fields, which can, e.g., fractionate soft tissue or even disintegrate solid objects, such as calculi. Our recent study demonstrates that an ultrasonically actuated medical needle can create cavitation phenomena inside water. However, the presence and behavior of cavitation and related bioeffects in diagnostic and therapeutic applications with ultrasonically actuated needles are not known. Using simulations, we demonstrate numerically and experimentally the cavitation phenomena near ultrasonically actuated needles. We define the cavitation onset within a liver tissue model with different total acoustic power levels. We directly visualize and quantitatively characterize cavitation events generated by the ultrasonic needle in thin fresh bovine liver sections enabled by high-speed imaging. On a qualitative basis, the numerical and experimental results show a close resemblance in threshold and spatial distribution of cavitation. These findings are crucial for developing new methods and technologies employing ultrasonically actuated fine needles, such as ultrasound-enhanced fine-needle biopsy, drug delivery, and histotripsy.

Research on the Environmental Impact of Industrial Noise Emitted By Mine and Mining Plants

Abstract The article presents the results of measurements of environmental noise accompanying the operation of devices operated in surface facilities of hard coal mines and noise generated in technological processes related to the loading and transport of spoil and materials necessary for production. The research results presented in the article are part of the program of “Consequences of excessive noise in the mining environment of hard coal mines”, the overarching goal of which is to reduce the emission of industrial noise. The research described in the article, carried out using the sampling method, was introduced in order to determine the actual values of noise levels emitted to the external environment from mines and mining plants, as well as to identify the acoustic power levels of devices and processes constituting the main sources of noise in mines. The obtained results showed that mines and mining plants are often not fully aware of the scale of the environmental impact of undesirable noise they emit. Therefore, the current periodic measurements of environmental noise should be replaced with permanent monitoring, which will be beneficial not only for the environment, residents of housing estates located near mines, but also for the mining plants themselves.

Structural–Acoustic Response Analysis of Variable Stiffness Laminates with Inherent Material Damping

Sound radiation and transmission loss characteristics of variable stiffness composite plate reinforced with the curvilinear fibers are investigated numerically. The formulation is developed using higher-order shear flexible finite element model combined with Helmholtz wave equation. The governing equations obtained using Hamilton’s approach are further solved through the modal super position method to analyze the vibration response under steady state excitation. The inherent material damping of the laminate is accounted through the modal damping calculated using the modal strain energy approach. The acoustic pressure of the variable stiffness laminates is estimated using the Raleigh integral. Subsequently, acoustic response characteristics such as acoustic power level, radiation efficiency, directivity pattern, and transmission loss from the laminates are predicted using the estimated sound pressure for various forcing frequencies. A parametric study covering a wide range of design variables including center and edge fiber angles, lamination scheme, thickness ratio, and boundary conditions on the acoustic sound behavior arising from the vibration of curvilinear fiber composite plate is detailed. This study reveals that the acoustic response of the curvilinear fiber composite plate is significantly influenced by the curvilinear fiber angles at the center/edge fiber angle of the layers. It is hoped that the results obtained here will be useful for designers in developing structures with desired acoustic response characteristics.

Control of Acoustic Extinguisher with Deep Neural Networks for Fire Detection

The search for fast and environmentally safe methods of fighting fires has been a particularly important topic in recent years. Many academic centres are conducting research on the use of Deep Neural Networks to detect flames. One of the most promising is the acoustic method of extinguishing flames. In theory, an acoustic extinguisher can be applied to extinguish fires of different classes because acoustic waves pass through solids, liquids, and gases. In principle, the technology described in the article can be used to extinguish B- and C-class fires when gases or liquids are burning. Until now, the known studies have been conducted only for low-power acoustic extinguishers. Therefore, there is a need to fill a theoretical and practical gap in this respect (scientific novelty). The result of the activities is the development of new techniques for extinguishing flames with the use of Deep Neural Networks, and then extinguishing flames using a high and very high power loudspeaker applied to the acoustic extinguisher. The main aim of this paper is to present the possibilities of using Deep Neural Networks to detect fires, as well as the results of research on the extinguishing of flames with the use of square waveforms with Amplitude Modulation (AM) for several frequencies, which is also a scientific novelty, including the minimum acoustic power and sound pressure level as a function of a distance from the output of the acoustic system. On this basis, it became possible to determine the minimum power delivered to the extinguisher and the minimum sound pressure level that causes the extinguishing effect at given input parameters.

Modification and Noise Reduction Design of Gear Transmission System of EMU Based on Generalized Regression Neural Network

In view of traction gear vibration and noise affecting the performance of the transmission system and the comfort of passengers when the electric multiple units (EMU) is running at high speed, taking the traction gear transmission system of an EMU as the research object by using Romax software to construct the parametric modification model of the gear transmission system based on gear modification theory. Combined with multibody dynamics, the vibration response characteristics of the transmission system are simulated and analyzed. A radiated noise prediction model is established using the acoustic boundary element method, based on the generalized regression neural network (GRNN). To further explore the influence of gear modification methods and parameters on vibration and noise characteristics and minimize gear transmission’s radiation noise. A particle swarm optimization (PSO) algorithm is designed to solve the optimal modification parameters. The simulation results reveal that after the optimization and modification, the gear transmission error is significantly reduced, the contact status is considerably improved, and the root mean square value of the acoustic power level is reduced by 13.10 dB, which is a reduction of 14%. It shows that the design can effectively reduce the radiation noise of EMU gear trans-mission system.

Numerical Investigation of the Sensitivity of the Acoustic Power Level to Changes in Selected Design Parameters of an Axial Fan

The noise generated by different types of fans used in the turbomachinery industry is a topic that has been studied for many years. However, researchers are still looking for a universal solution to reduce noise while maintaining the performance of these machines. This paper, as a contribution to the research, presents the results of numerical investigations of an axial fan installed in a pipeline with a circular cross-section. In particular, the focus was on investigating the sensitivity of the sound power level to changes in selected design and operational parameters of this fan. The simulation studies used the unsteady Reynolds-averaged Navier–Stokes (URANS) approach and the Ffowcs Williams–Hawkings (FW-H) analogy implemented in Ansys Fluent.

CFD Analysis of Journal Bearing by Modifying The Roughness Surface

A journal bearing is a machine part that is used to ensure that the shaft always rotates in the opposite direction of the axis. Journal bearings are chosen because they are well-suited for use in mechanical systems that demand precision, speed, and a high load capacity. Recent years have seen an increase in research on how to improve the tribological performance of bearings by considering the design/architecture of these bearings. Numerous scientists have developed numerous methods for measuring pressure distribution, load-carrying capacity, acoustic power level, force friction, and cavitation phenomena in order to improve the performance of tribology, particularly in journal bearings. As a result, hydrodynamic lubrication was used in the investigation. The investigation was conducted using a computational fluid dynamics (CFD) three-dimensional journal bearing model that took cavitation into account. Additionally,the location of the heterogeneous rough/smooth bearing pattern was modified, as was the shaft rotational speed. The results of this study indicate that when the surface roughness is applied to journal bearings in a variety of locations with heterogeneous rough/smooth bearing patterns, the tribological performance of journal bearings is significantly improved, and that high shaft rotational speed has a significant effect on the tribological performance of journal bearings.

Response Surface Analysis of DIB Nozzle Geometry on Acoustic Power Level using Central Composite Design of Experiment

The critical process parameters in manufacturing dry ice blasting nozzle geometry directly related to particle jet velocity. Many studies focused on its performance without considering the noise emission due to high operating pressure. This paper, a numerical simulation study was performed using Ansys Fluent to investigate the effect of nozzle geometry of single-hose dry ice blasting on the acoustic power level. The process of modelling the two-way mass momentum and energy exchange between two phases was successfully solved iteratively in the two-way mass momentum model and the energy exchange between the two phases. It was found that the value of noise emission reaches a maximum level when the shortest convergent angle of 20° with a minimal convergent length of 50 mm and a maximum length of 300 mm is introduced. Besides, the peak value of acoustic power level swell up to 146 dB occurs at a nozzle area ratio of 20 without influencing by convergent angle and extending the divergent length highly influencing noise reduction as less than 143.5 dB for a divergent length of 700 mm.

Study and Design Frontal Area of a Car to Curtail Aerodynamic Noise

Abstract: In this field of comparative research study, comparison of two car model, a standard car and an optimized car with respect to aerodynamic analysis/aeroacoustics analysis with the help of CFD software Ansys 2019 R2 version is taken in consideration to compare the results and get to know if the optimized car model has reduction in the generation of aerodynamic noise when it travels at four different speeds (30 m/s, 40 m/s, 50m/s and 60m/s). For carried out aeroacoustics/aerodynamic noise analysis two main model are used turbulence model and an acoustics model. For turbulence model and K-epsilon model is used as it is widely used for getting turbulence generation and for acoustics model a Broadband noise model is used to generate the results through numerical simulation and data sources. First a standard sedan car is modelled in Onshape CAD tool and aeroacoustics analysis is carried out on this standard sedan car to get to know the source of aerodynamic noise. From the standard car results made changes in the sedan car geometry like giving fillets to point/sharp edges of wheel arcs, front bumper, hood-line, fender and start of roofline from A-pillar, providing under-flush, optimizing A-pillar beam and optimizing outside rear view mirror and making them fully camera integrated mirror to reduce wake. After optimizing standard geometry carried out aerodynamic analysis with the same four different speed given for standard car (30 m/s, 40m/s, 50m/s and 60 m/s). Generated contour plots and isosurface from CFX for flow characteristics and acoustic sound source with various model like Proudman’s acoustic power level in Db, Curle surface acoustic power level in decibels (dB) and also, Lilley S total noise source to show the sources of noise and how many decibels of noise is generated from those sources. Maximum of 100 decibels of noise is generated from the front bumper and a minimum of 80 decibels were monitored in the results process after comparing the results with standard car which has noise nearly 120 decibels with high fluctuations of turbulence kinetic energy and decrease in its pressure level. Keyword: Aeroacoustics, Aerodynamic noise, Aeolin sound, Fluid dynamics, NVH (noise, vibration and harshness) and CFD (computational fluid dynamics).

Aerodynamic robustness optimization and design exploration of centrifugal compressor impeller under uncertainties

Aerodynamic robustness optimization of centrifugal compressor impeller under multiple uncertainties is an arduous task, due to high dimension, meta modelling workload and trial and error optimization, and an automatic optimization process is often treated as a black box, the underlying mechanism are often not well understood and explored. This paper aims to provide an efficient robustness optimization procedure and explore the underlying physical mechanism for centrifugal compressor impeller under operational and geometric uncertainties. A novel approach is proposed for the multi-objective aerodynamic robustness optimization and design exploration of a centrifugal compressor impeller. A neural-network-based Kriging model is constructed and integrated into the aerodynamic robustness optimization The correlation between the design variables and performance parameters are explored from optimization and directly visualized by self-organizing mapping. Compared to the initial impeller, the average pressure ratio of the optimized impeller increases by 9.3%, the average isentropic efficiency increases by 6.7%, the standard deviations of pressure ratio and efficiency decrease by 7.5% and 15.4% respectively, and the acoustic power level decreases by 11dB. The neural-network-based Kriging model exhibits preferable accuracy for uncertain approximation modeling. The data visualization and interpretation facilitate designers to perform efficient design optimizations. The proposed approach supports design explorations for different applications of turbomachinery.

CFD Simulation of Air Flow Behaviour at Different Flow Rates in a Turkish Woodwind Instrument (Turkish Treble Recorder)

In musical instruments, the geometric design and material features of the instrument are the most important factors that determine the sound characteristics of the instrument. Traditional replication and experiment-based handcrafting methods are predominant in the production of Turkish Folk Music wind instruments. The instrument manufacturing and standardization approaches, which include the relevant rules of physics and engineering practices, are limited purely to prototype studies for scientific research purposes. It is almost impossible to find studies on Turkish Folk Music wind instrument design and production involving computer aided design and engineering applications. In this study, an example Turkish woodwind instrument, the Turkish Treble Recorder (dilli kaval) is considered, and the air flow behaviour and acoustic (sound) power magnitudes that occur at different air flow rates are simulated in a computer environment using a Computational Fluid Dynamics (CFD) simulation technique. In the study, numerical and visual outputs related to air behaviour at different air flow rates that may be used in the instrument manufacturing phases were obtained. Acoustic power level was also measured experimentally. Simulation outputs (the acoustic power level) were compared to experimental results in order to validate the simulation results. The comparison revealed that the highest relative difference was calculated as 13.32(%). This value indicated that the simulation results were reasonably consistent with the results of the experimental measurement. Additionally, this study was constructed as a case study that may provide reference for future research studies in this field.

Bolted connected optimization of composite-to-aluminium structure based on vibro-acoustic control: Numerical simulation and experimental

Bolted connection is an important connection form between composite laminate plate and metal frame structure. The type and location of the connection bolts are of great influence on the structural strength, stiffness and structural vibro-acoustic properties. To achieve the goal of reduction vibration and noise, the bolted connection form optimization of the panel structure is investigated. Bolts stiffness parameter (bolt diameter, etc) and the distribution location are defined as design variables, the bolted connection form optimization function which aim to minimize of acoustic radiation power is established. The composite-to-aluminium panel structure under harmonic excitation for example, the numerical analysis of bolted connection form optimization is implemented. The results show that the acoustic radiation power level and total level of the panel structure are significantly decreased. In the end, the numerical analysis results are verified by model experiment, which validated the feasibility and effectiveness of the proposed method. The results in present work provides more understanding the design and application of the composite-to-aluminium panel structure with bolted connection.

Determining structural damping and vibroacoustic characteristics of a non-symmetrical vibrating plate in free boundary conditions using the modified Helmholtz equation least squares method

This paper presents a comprehensive study to determine the structural damping and vibroacoustic responses of an arbitrarily shaped planar structure subject to non-contact acoustic excitations under free boundary conditions using a modified HELS (Helmholtz equation least squares) method. The input data consist of the normal surface velocities measured by a laser vibrometer at a discrete number of points on the source surface, and the acoustic pressures measured by a small array of microphones in the field. The normal surface velocity distribution over the entire surface of the plate is then reconstructed by the HELS method and compared to benchmark data. Similarly, the reconstructed acoustic power level spectra are compared to those measured by the array of microphones. The reconstructed vibroacoustic quantities using the modified HELS method are interrogated, and the method's accuracy evaluated. Specifically, a limited number of normal velocity data points on the surface of the target structure are taken as input to the HELS formulations. The reconstructed velocity distributions on the entire surface of the structure with much higher density even for areas of the target structure with little or no input data were compared to the benchmark results. It is worth noticing that no other vibroacoustic technologies are available that allow for complete reconstruction of the normal surface velocity distributions based on limited input data. The dimensionless damping ratio of the structure is also determined. Results indicate that the dimensionless damping ratio for metals, for instance steel, is frequency dependent rather than a constant. Moreover, the empirical formulation developed in this study enables one to get the dimensionless damping ratios continuously over the frequency range from 0 to 10,000 Hz.

Acoustic analysis of ship propeller using CFD

The acoustic levels generated by ship propeller are very much important in the design and development of the propeller from stealth technology point of view. The KCS SVA 1193 model of propeller geometry has been taken from the literature. The complex 3D geometry of the propeller is created using CATIAV5. The propeller geometry, surrounded by the sea water, has been considered by creating the fluid domain around the propeller. The acoustic levels, generated by the propeller, are computed using commercial software package ANSYS FLUENT. The unstructured mesh is generated in the fluid domain. The k–∈ standard turbulence model is selected to capture the viscous effects. The velocity at the inlet, pressure at outlet and moving frame of reference boundary conditions are used for computational analysis. Broadband noise model is used to capture the effects of the acoustic waves. The thrust and torque have been estimated for the chosen propeller. In this analysis, the acoustic power level of the propeller is captured and the non-dimensional coefficients are calculated.

초고속 터보기계의 회전 속도에 대한 공력-소음 연구

This study is to numerically investigate the Aero-Acoustics of Turbocharger compressor. The turbocharger compressor is high-speed turbomachinery that rotates faster than 200,000 RPM. The Aero-Acoustics with five different rotational speeds (120,000, 150,000, 180,000, 200,000, and 220,000 RPM) is used herein. The fluid domain is designed by CATIA V5R21 and analyzed by ANSYS FLUENT V19.1 with compressible momentum equation. The Pressure-velocity coupling method of the solver is the coupled algorithm and calculated by a pressure-based method. Numerical analysis of the aero-acoustics by broadband noise sources model provides calculated sound-source and acoustic-level based on steady RANS. At the industrial site, it is important to quickly analyze the noise source. APL (Acoustic Power Level) with five different rotational speeds and sound characteristics based on flow factor at the compressor wheel was numerically calculated for the noise-based design. The maximum APL is located at blade tips in case of 120,000, 150,000 and 180,000 RPM. In the case of 200,000 RPM, the maximum APL is located at splitter tips. At more than 220,000 RPM, the maximum APL is located at the balancing cutting section of the wheel. In order to optimally design the high-speed turbomachinery, cutting sections and side locations of the wheel are essential factors to reduce physical noise.

Numerical simulation of HIFU with dual transducers: The implementation of dual-phase lag bioheat and non-linear Westervelt equations

The high intensity focused ultrasound (HIFU) has been proved to be effective and promising in local tumor treatment. Although HIFU utilization with multi transducers goes back several decades, the procedure numerical simulation, to the best of author knowledge, has not been conducted. In the present study, computational modeling of the HIFU with two crossing transducers at various arrangements was carried out to determine the treatment effectiveness. The coupled dual-phase bioheat transfer and non-linear Westervelt equations were solved to determine the acoustic and temperature fields, respectively. Moreover, the thermal dosage criteria were applied to obtain an effective thermo-ablated area in the targeted tumor. The developed model included the non-Fourier heat transfer law, and the scattering and absorption of acoustic waves at higher harmonics. The effect of transducers position and orientation, and the acoustic power level on the produced pressure and thermal fields, were investigated. The presented results showed that by increasing the sonication amplitude, the effective area has an average enhancement of about 0.27, 7.08 and 27.9% for 3, 5 and 7 W power levels, respectively. Moreover, based on the tumor shape, a suitable combination of transducer location, orientation, and power level can be selected to achieve optimum treatment.

Optimizing the aerodynamic noise of an automobile claw pole alternator using a numerical method

The aerodynamic noise of an alternator, which is difficult to predict due to the complex internal flow, has become an issue for vehicles in recent years. To study the acoustic characteristics of the vehicle claw pole alternator, a numerical simulation method is proposed in this paper to predict its aerodynamic noise. First, a Scale Adaptive Simulation (SAS) in the numerical calculation is used to calculate the flow field. Then, the Ffowcs-Williams and Hawkings acoustic model is applied to calculate its acoustic characteristics. Additionally, a series of experiments are performed to verify the accuracy of the simulation method. According to the experimental data, it is determined that the dominant influencing orders for the overall noise are the 8th, 16th and 24th orders. Comparing the simulation results with the experimental results, the prediction errors are −0.67 dBA, −2.9 dBA and −3.22 dBA in the acoustic power levels of the 8th, 10th and 12th orders, respectively, which are all within 4%. Finally, the Vector Composition Method (VCM), considering the mass flow rate and low noise, is applied to ameliorate the distribution of the spectral energy by optimizing the distribution angles of the rear fan. Moreover, a prototype is produced to verify the practical application of this method. After optimization, the numerical results indicate that the mass flow rate of the rear fan is reduced by 5.172%, while the front fan is increased by 5.128%. The experimental results indicate that the maximum increasing overall noise on the 6th order is 4.7 dB and the increasing values of the 10th and 14th orders are all in a limited range. Additionally, the maximum decreasing overall noise amounts of the 8th order and 12th order exceed 5.1 dB and the average decreasing amount exceeds 2.5 dB; that is to say, this method has a remarkable effect on the acoustic noise spectral structure.

Optimizing nozzle convergent angle using central composite design on the particle velocity and acoustic power level for single-hose dry ice blasting nozzle

One of the important parameters in developing dry ice blasting nozzle is the high-speed dry ice pellets. However, many studies focus primarily only on its performance without considering the noise emission that comes from an operating nozzle. In this method, the central composite optimization tool has been used. The two-way mass momentum and energy exchange are successfully modeled using the two-way mass momentum model. As an attempt to theoretically verify the model accuracy, a comparison is conducted on the density, pressure, temperature, as well as Mach number ratios corresponding to various ratios of nozzle area. In return, the smallest value of the convergent angle results in the highest velocity of 516.75 m s−1, as well as the highest level of the acoustic power level of 144.36 dB. Besides, one of the vital influencing factors on the emitted acoustic power level is the turbulence intensity, which can achieve a maximum of 1% intensity for an angle of 20° at the throat section. Besides, the same negative sensitivity of around − 0.99% is provided by the velocity and acoustic power level, which is highly responsive toward the convergent angle variation. Furthermore, the optimum nozzle convergent angle for the minimization of the acoustic power level and maximization of the velocity is 7.03°. The novelty of this research lies in the findings on the effective convergent angle of the dry ice blasting nozzle that accelerates the particle flow and minimizes the noise emission from the operating nozzle.

Effect of Blade Outlet Angle on Acoustics of Marine Centrifugal Pump

To research the effect of blade outlet angle on acoustics of marine centrifugal pump, the unsteady numerical simulation analysis of the four models is carried out and the dipole source of pump shell is extracted. The constraint modal of pump, interior sound pressure level (SPL), exterior acoustic directivity and sound power level are obtained. The results show that five and six SPL peaks appear at BPF and blade frequency multiplier in the pump inlet and outlet, respectively, the SPL peak value is the largest at blade passing frequency (BPF), and the interior acoustics propagates to inlet and outlet directions, and to outlet more significantly. The exterior acoustic directivity in the four models is the same in all directions, and the blade outlet angle has little influence on the changes of exterior acoustic directivity. The SPL at BPF and 2BPF in Y = 0 plane is significantly smaller than that in X = 0 and Z = 0 planes, and the difference of maximum SPL at BPF is 7.2 dB and 8.0 dB and that at 2BPF is 7.6 dB and 6.4 dB, respectively. The sound power level is maximum at 2BPF, and that at the BPF and 2BPF increases first and then decreases with the blade outlet angle increases. When the blade outlet angle is 40o, the interior and exterior acoustic performances are better. The experimental value of the SPL in model 35 is basically consistent with the simulated value, which fully indicates that the numerical simulation analysis has high accuracy and provides support for the credibility of the acoustic simulation results.

Acoustic Power Prediction of High BPR Turbofan Engine with Chevron Nozzle during Take-off and Landing

Aircraft noise is a major cause of noise pollution around the vicinity of an airport. Jet noise from engines is a common condition, which has considerable impact on overall sound levels. Adding chevron pattern at the fan nozzle is one of the noise reduction enhancements found in current turbofan engine design features. This paper aims to study the power level of sound created in jet shear from the combination of ambient stream, fan and exhaust gas. Computational fluid dynamic modelling of a high bypass turbofan engine with a round shape and chevron nozzle were carried out during takeoff and landing conditions. It was found that during take-off, the acoustic power level of the engine without a chevron nozzle was 105.95 dB, while the chevron nozzle was capable of reducing the sound level to 43.57 dB. During landing, the sound level of the round shape and chevron nozzle model were 145.77 dB and 47.51 dB, respectively. The turbulent intensity area at the fan cowling nozzle, where the ambient air stream and bypassed air from the fan mixed together, produced the highest sound power level. Therefore, slower aircraft speed during final approach produced a higher noise level than during take-off due to higher turbulent intensity and larger jet shear area around the high bypass fan cowling nozzle. The chevron pattern nozzle was capable of reducing turbulent intensity, which in turn reduced the acoustic power level.