Additional noise reduction with diffracting elements on barriers using numerical and standard calculation methods

2021 ◽  
Vol 263 (3) ◽  
pp. 3118-3129
Author(s):  
Frits van der Eerden ◽  
Rafal Kurylek ◽  
Sandra Blaak ◽  
Erik Salomons ◽  
Arno Eisses ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Element Model ◽  
Calculation Model ◽  
Barrier Effect ◽  
Additional Element ◽  
Quarter Wavelength ◽  
Additional Noise ◽  
Numerical Finite Element ◽  
Point To Point ◽  
Standard Calculation

The noise reduction of a (low) barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. A so-called Whiswall or WHIStop deflects sound upwards for specific frequencies. Measurements for a 1.1 meter high Whiswall and for a 1.1m barrier are compared in a separate paper. The enhanced barrier effect is measured at a short distance behind the barrier, for several situations. In this paper these measurements are compared with the results of a numerical finite element model (FEM) to validate this model. Next, the noise reduction is calculated at long ranges, up to 600 meters, for different point-to-point scenarios representative for road and rail traffic. A numerical parabolic equation method (PE) is coupled to the FEM model and a representative downwind condition is taken into account. The results at longer distance are used to design an engineering method for the enhanced barrier effect that can be used in standard noise calculation models, such as the Dutch national calculation model (SRM2) or the ISO 9613-2 standard.

Additional noise reduction with diffracting elements on barriers: experimental testing

2021 ◽  
Vol 263 (4) ◽  
pp. 2654-2664
Author(s):  
Wout Schwanen ◽  
Mark Mertens ◽  
Ysbrand Wijnant ◽  
Willem Jan van Vliet
Keyword(s):  
Noise Reduction ◽  
Experimental Testing ◽  
Low Noise ◽  
Motor Vehicles ◽  
Additional Element ◽  
High Noise ◽  
Quarter Wavelength ◽  
Noise Barrier ◽  
Sound Reduction ◽  
Development And Validation

The noise reduction of a (low) noise barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. The so-called WHISwall or WHIStop deflects sound upwards for specific frequencies creating an additional sound reduction. Different experiments on the WHISwall and WHIStop are performed as input for model validation. The development and validation of the model are described in a separate paper. In this paper the measurement campaign and its results are presented. We performed measurements on two setups. The first setup consists of a 1.1 meter high WHISwall, a 1.1m high noise barrier and a reference section (without noise measure). Measurements have been conducted with both an artificial sound source and pass by measurements with light and heavy motor vehicles. In a second test setup, the WHIStop was placed on top of a 4 meter high noise barrier and the diffraction was determined according the European standard EN 1793-4.

scholarly journals Effect of spatial distribution of fibers on elastic properties of unidirectional carbon/carbon composites

2021 ◽  
Vol 309 ◽  
pp. 01214
Author(s):  
M.V.N Mohan ◽  
Ramesh Bhagat Atul ◽  
Vijay Kumar Dwivedi
Keyword(s):  
Finite Element ◽  
Spatial Distribution ◽  
Elastic Properties ◽  
Element Model ◽  
Experimental Methods ◽  
Design Stage ◽  
Carbon Composites ◽  
Numerical Predictions ◽  
Numerical Finite Element ◽  
Very High

Carbon/Carbon composites finds its applications in several high temperature applications in the field of Space, Aviation etc. Designing of components or sub systems with carbon/carbon composites is a challenging task. It requires prediction of elastic properties with a very high accuracy. The prediction can be normally done by analytical, numerical or experimental methods. At the design stage the designers resort to numerical predictions as the experimental methods are not feasible during design stage. Analytical methods are complex and difficult to implement. The designers use numerical methods for prediction of elastic properties using Finite Element Modeling (FEM). The spatial distribution of fibers in matrix has an effect on results of prediction of elastic constants. The generation of random spatial distribution of fibers in representative volume element (RVE) challenging. The present work is aimed at study of effect of spatial distribution of fiber in numerical prediction of elastic properties of unidirectional carbon/carbon composites. MATLAB algorithm is used to generate the spatial distribution of fibers in unidirectional carbon/carbon composites. The RVE elements with various random fiber distributions are modeled using numerical Finite element Model using ABAQUS with EasyPBC plugin. The predicted elastic properties have shown significant variation to uniformly distributed fibers.

scholarly journals Non linear analysis of vibrations generated by a contact with friction

2010 ◽  
pp. 305-316
Author(s):  
Anissa Meziane ◽  
Laurent Baillet
Keyword(s):  
Physical Phenomenon ◽  
Element Model ◽  
Interface State ◽  
Linear Analysis ◽  
Bimaterial Interface ◽  
Dynamic Rupture ◽  
Elastic Solids ◽  
Nonlinear Analyses ◽  
Beam System ◽  
Numerical Finite Element

The aim of this paper is to study vibrations generated at contact with friction for two different applications. The first one is an investigation of friction-induced vibrations of a beam-on-beam system in contact with friction. For this study the complementary use of linear and nonlinear analyses drives to the understanding of physical phenomenon induced in these vibrations. The second parts consists in investigating numerically dynamic rupture of a bimaterial interface. The numerical Finite Element model is composed of two homogeneous and isotropic elastic solids which are brought in contact with friction by remote normal compression and shear traction. The rupture is nucleated by decreasing instantaneously the friction coefficient to zero at nucleation area. The properties of the obtained ruptures (velocity, generated waves, interface state…) are analyzed.

Eddy Current Loss and Shielding Research of the Tank in Power Transformer

2012 ◽  
Vol 468-471 ◽  
pp. 1086-1089 ◽  
Author(s):  
Yong Ming Xu ◽  
Chao Du ◽  
Da Wei Meng
Keyword(s):  
Magnetic Field ◽  
Eddy Current ◽  
Power Transformer ◽  
Element Model ◽  
Eddy Current Loss ◽  
Calculation Model ◽  
Ultrahigh Pressure ◽  
Tank Wall ◽  
Current Loss ◽  
Leakage Magnetic Field

The problem about the eddy current loss which is caused by leakage magnetic field in ultrahigh pressure large capacity power transformer is becoming more extrusive. It is very significant to research the power transformer leakage magnetic field and eddy current loss on the tank wall thoroughly and accurately. 3D finite element model of power transformer leakage magnetic field and eddy current loss is established in this paper, the eddy current loss on the tank wall is calculated and the distribution is analyzed. For the eddy current loss could be reduced by magnetic shielding, new calculation model are established respectively, then eddy current loss on tank wall could be got with shielding. The best size and location of the shielding could be analyzed after changing the height of the shielding, which provided the important evidence to reduce tank wall eddy current loss effectively. The calculating methods have been proved to be accuracy after experiment.

Аpplication of the mathematical model of human torso for modeling abbreval influence in wound ballistics

2020 ◽  
Vol 22 (3) ◽  
pp. 132-139
Author(s):  
A. V. Denisov ◽  
M. D. Stepanov ◽  
N. A. Haraldin ◽  
A. V. Stepanov ◽  
A. I. Borovkov ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Element Model ◽  
Mechanical Action ◽  
Calculation Model ◽  
Calculation Results ◽  
Automated Processing ◽  
Original Calculation ◽  
Using Data ◽  
The Mathematical Model ◽  
Selection Of

Abstract. In the work, a review of scientific articles on the behavior of tissues and organs of the human body under local mechanical effects on it, as well as a description of the physico-mechanical properties of biological materials. The selection of mechanical behavior for each biological material as part of a mathematical model of the human torso was carried out, its finite element model was created, validation experiments were modeled using data presented in the literature. An original calculation model of a human torso with a tuned interaction of organs with each other was developed. Contact interaction parameters are determined. The developed computational model of a human torso was verified based on data from open sources for an experiment with mechanical action by a cylindrical impactor. An algorithm for processing pressure and acceleration graphs has been implemented in order to obtain tolerance curves. A specialized modular program has been created for the automated processing of calculation results and the output of the main results. 42 numerical tests were carried out simulating the entry of a steel ball into each of 21 zones for power engineers of 40 and 80 J. According to the results of the tests for each organ, pressure and acceleration tolerance curves were obtained, animations of the behavior of organs under shock were created, visualization of the pressure field propagation in organs was obtained torso.

The sagittal curvature of the spine can be a leading cause of scoliosis in pediatric spine

2021 ◽  
Author(s):  
S Pasha
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Early Stage ◽  
Element Model ◽  
Sagittal Profile ◽  
Deformation Pattern ◽  
Element Simulation ◽  
Curve Deformation ◽  
Numerical Finite Element ◽  
Deformation Patterns

The etiology of the adolescent idiopathic scoliosis (AIS) remains unknown. Variations in the sagittal profile of the spine between the early stage scoliotic and non-scoliotic pediatric patients have been shown. However, no quantitative study has shown the link between the sagittal profile and 3D deformity of the spine. 126 right thoracic scoliosis with spinal and 3D reconstructions were included. A 2D finite element model was developed for each of the sagittal curve types without any deformity in the frontal or axial planes. Physiological loadings were determined from the literature and were applied in the finite element model. The 3D deformation patterns of the models were compared to the 3D spinal patterns of the AIS with the same sagittal type. A significant correlation was found between the 3D deformity of the scoliotic curves and the numerical finite element simulation of the corresponding sagittal profile as determined by pattern correlation, p<0.001. The sagittal curve deformation patterns corresponded to the spinal deformities in the patients with the same sagittal curvature. Finite element models of the spines, representing different sagittal types in 126 AIS patients showed that deformation pattern of the sagittal types changes as a function of the spine curvature and associates with the patterns of 3D spinal deformity in AIS patients with the same sagittal curves. This finding provided evidence that the sagittal curve of the spine can determine the deformity patterns in AIS.

Shape Optimisation of Multi-Chamber Acoustical Plenums Using BEM, Neural Networks, and GA Method

2016 ◽  
Vol 41 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Ying-Chun Chang ◽  
Ho-Chih Cheng ◽  
Min-Chie Chiu ◽  
Yuan-Hung Chien
Keyword(s):  
Noise Reduction ◽  
Boundary Element ◽  
Transmission Loss ◽  
Real Data ◽  
Element Model ◽  
Shape Optimisation ◽  
Design Data ◽  
Input Design ◽  
Speed Up ◽  
Fixed Space

Abstract Research on plenums partitioned with multiple baffles in the industrial field has been exhaustive. Most researchers have explored noise reduction effects based on the transfer matrix method and the boundary element method. However, maximum noise reduction of a plenum within a constrained space, which frequently occurs in engineering problems, has been neglected. Therefore, the optimum design of multi-chamber plenums becomes essential. In this paper, two kinds of multi-chamber plenums (Case I: a two-chamber plenum that is partitioned with a centre-opening baffle; Case II: a three-chamber plenum that is partitioned with two centre-opening baffles) within a fixed space are assessed. In order to speed up the assessment of optimal plenums hybridized with multiple partitioned baffles, a simplified objective function (OBJ) is established by linking the boundary element model (BEM, developed using SYSNOISE) with a polynomial neural network fit with a series of real data – input design data (baffle dimensions) and output data approximated by BEM data in advance. To assess optimal plenums, a genetic algorithm (GA) is applied. The results reveal that the maximum value of the transmission loss (TL) can be improved at the desired frequencies. Consequently, the algorithm proposed in this study can provide an efficient way to develop optimal multi-chamber plenums for industry.

scholarly journals Exo-Skeletal Engine: Novel Engine Concept

2003 ◽  
Author(s):  
Christos C. Chamis ◽  
Isaiah M. Blankson
Keyword(s):  
Noise Reduction ◽  
Open Channel ◽  
Jet Noise ◽  
Element Model ◽  
Combined Cycle ◽  
Engine Design ◽  
Potential Benefits ◽  
Immense Potential ◽  
Bypass Ratio ◽  
Engine Concept

The Exo-Skeletal Engine concept represents a new radical engine technology with the potential for a substantial revolution in engine design. It is an all composite drum rotor engine in which conventional heavy shafts and discs are eliminated and are replaced by rotating casings that support the blades in spanwise compression. Thus the rotating blades are in compression rather than in tension. The resulting open channel at the engine centerline has immense potential for jet noise reduction, and can also accommodate an inner combined-cycle thruster such as a ramjet. The Exo-Skeletal Engine is described in some detail with respect to geometry, components and potential benefits. Initial evaluation, results for drum rotors, bearings and weights are summarized. Component configuration, assembly plan and potential fabrication processes are also identified. A finite element model of the assembled engine and its major components are described. Preliminary results obtained thus far show at least 30 percent reduction of engine weight and about 10 db noise reduction, compared to a baseline conventional high bypass-ratio engine. Potential benefits in all aspects of engine technology are identified and tabulated. Quantitative assessments of potential benefits are in progress.

Vibration and Noise Reduction Analysis of Snowplow’s GearBox Case Based on Modal Analysis

2016 ◽  
Vol 13 (10) ◽  
pp. 7426-7432
Author(s):  
Xiangyang Jin ◽  
Jun Wang ◽  
. Zhihui ◽  
Zhihui Sun ◽  
Qiyun Yang ◽  
...  
Keyword(s):  
Finite Element ◽  
Noise Reduction ◽  
Modal Analysis ◽  
Vibration Mode ◽  
Element Model ◽  
Element Analysis ◽  
Modeling Technology ◽  
Comparison Results ◽  
Vibration Noise ◽  
Excessive Noise

Study has been conducted on how, where and why does excessive noise generate on the gear-box of the snowplow, and, measures for improvement have been presented. As well, analysis to the generation mechanism of vibration noise of gearbox and gears has been made, to find out the source of the noise. Next, a precise model of the gearbox, built by using 3D modeling technology, was translated into finite element model to make the modal analysis. Through analyzing characteristics of each vibration mode, positions of the gearbox case on which a vibration is most likely to be generated have been determined. To check the accuracy of theoretical calculation, vibration and noise tests were made to the gearbox. Specific measures for improvement were then put forward by combining results from both finite element analysis and experimental analysis. The comparison results showed that: the improved gearbox case had a significant effect on noise reduction, and the goal of reducing vibration and noise was achieved.

Numerical Assessment of Multi-Splitter Mufflers Using Neural Networks, the Boundary Element Method, and the Genetic Algorithm

2011 ◽  
Vol 58-60 ◽  
pp. 1049-1055 ◽  
Author(s):  
Min Chie Chiu
Keyword(s):  
Genetic Algorithm ◽  
Noise Reduction ◽  
Boundary Element ◽  
Matrix Method ◽  
Transmission Loss ◽  
Real Data ◽  
Element Model ◽  
Design Data ◽  
Input Design ◽  
The Cost

Recently, research on new mufflers lined with sound-absorbing material has been addressed in the industrial field. On the basis of the transfer matrix method and the stiffness matrix method, most researchers have explored noise reduction effects. Yet, the maximum noise reduction of a compact silencer equipped with sound-absorbing splitters within a constrained space, which often occurs in modern industries, has been ignored. Therefore, the optimum design of mufflers becomes essential. In this paper, a one-chamber muffler equipped with multiple sound-absorbing panels within a fixed length is assessed. In order to facilitate the assessment of optimal mufflers having multiple sound-absorbing splitters, an approximated simplified objective function (OBJ) is established in advance by linking the boundary element model (BEM) with a polynomial neural network fitted with a series of real data, input design data (muffler dimensions) and output data obtained by BEM simulation. To assess the optimal mufflers, a genetic algorithm (GA) is applied. Before the GA operation can be carried out, the accuracy of the mathematical models must be checked using the experimental data. On the basis of the fixed total thickness of the splitters, the open area of the flowing channel can be assured. Therefore, not only the influence of the backpressure can be minimized, but also the cost of the sound absorbing splitters can be economically saved. Optimal results reveal that the maximum value of the sound transmission loss (STL) can be improved at the targeted frequencies. Consequently, the optimum algorithm proposed in this study provides an efficient way to find a better silencer for industry.

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