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Viewing 181 to 210 of 7641
2016-06-15
Technical Paper
2016-01-1807
Olga Roditcheva, Lennart Carl Lofdahl, Simone Sebben, Pär Harling cEng, Holger Bernhardsson
Abstract This paper presents an experimental study of aeroacoustical sound sources generated by the turbulent flow around the side mirror of a Volvo V70. Measurements were carried out at the Volvo Cars aerodynamical wind tunnel (PVT) and at the aeroacoustical wind tunnel of Stuttgart University (FKFS). Several different measurement techniques were applied in both tunnels and the results were compared to each other. The configurations considered here were: side mirror with a cord and without the cord. The results discussed in this paper include intensity probe measurements in the flow around the side mirror, sound source localization with beamforming technique using a three-dimensional spherical array as well as standard measurements inside the car with an artificial head. This experimental study focused on understanding the differences between testing at the PVT and FKFS.
2016-06-15
Technical Paper
2016-01-1810
Marie Escouflaire, Nicolas Zerbib, David Mas, Nicolas Papaxanthos, Saad Bennouna, Emmanuel Perrey-Debain, Boureima Ouedraogo, Solène Moreau, Jean Michel Ville
Abstract In the framework of noise reduction of HVAC (Heating, Ventilating and Air Conditioning) systems designed for cars, the present study deals with the numerical prediction of aeroacoustics phenomena encountered inside such devices for industrial purposes, i.e. with a reasonable CPU time. It is then proposed in this paper to assess the validity of the chaining, via Lighthill-Curle analogy, of a DES (Detached Eddy Simulation) resulting from the CFD code OpenFOAM (ESI Group) versus a RANS-LES (Large Eddy Simulation) and a BEM calculation resulting from the Vibro/Aeroacoustics software VA One (ESI Group) on an academic case of air passing through a rectangular diaphragm at a low Mach number. The BEM code being parallelized, the performances of DMP (Distributed Memory Processing) solution will also be assessed.
2016-06-15
Technical Paper
2016-01-1811
Anders Rynell, Gunilla Efraimsson, Mattias Chevalier, Mats Abom
Abstract To obtain realistic noise characteristics from CAA studies of subsonic fans, it is important to prescribe properly constructed turbulent inflow statistics. This is frequently omitted; instead it is assumed that the stochastic characteristics of turbulence, absent at the initial stage, progressively develops as the rotor inflicts the flow field over time and hence that the sound generating mechanism governed by surface pressure fluctuations are asymptotically accounted for. That assumption violates the actual interplay taking place between an ingested flow field and the surface pressure fluctuations exerted by the blades producing noise. The aim of the present study is to examine the coupling effect between synthetically ingested turbulence to sound produced from a subsonic ducted fan. The steady state inflow parameters are mapped from a precursor RANS simulation onto the inflow boundaries of a reduced domain to limit the computational cost.
2016-06-15
Technical Paper
2016-01-1805
Florian Zenger, Clemens Junger, Manfred Kaltenbacher, Stefan Becker
Abstract A low pressure axial fan for benchmarking numerical methods in the field of aerodynamics and aeroacoustics is presented. The generic fan for this benchmark is a typical fan to be used in commercial applications. The design procedure was according to the blade element theory for low solidity fans. A wide range of experimental data is available, including aerodynamic performance of the fan (fan characteristic curve), fluid mechanical quantities on the pressure and suction side from laser Doppler anemometer (LDA) measurements, wall pressure fluctuations in the gap region and sound characteristics on the suction side from sound power and microphone array measurements. The experimental setups are described in detail, as to ease reproducibility of measurement positions. This offers the opportunity of validating aerodynamic and aeroacoustic quantities, obtained from different numerical tools and procedures.
2016-06-15
Technical Paper
2016-01-1775
Thomas Resch, Oliver Knaus, Siegmund Thomann, Stephan Brandl
Abstract Modern powertrain noise investigation in the development process and during trouble shooting is a combination of experiment and simulation. In simulation in recent years main focus was set on model completeness, consideration of all excitation mechanisms and efficient and stabile numerical algorithms. By that the total response of the virtual powertrain is already comparable to the overall noise level of the real powertrain. Actual challenge is to trace back the overall response to its main excitation and noise generating mechanism as well as to their main driving parameters to support the engineer not only in reaching absolute values, but also to derive the root cause of a response or potential problem and to get hints on how to improve the specific behavior. Approaches by parameter sensitivity studies are time consuming and not unambiguous.
2016-06-15
Journal Article
2016-01-1766
Thomas Deighan, Nozomu Kato, Kiyofumi Sato
Abstract An engine configuration has a significant influence on the sound quality from the powertrain. Whilst the fundamental order content can be readily apparent from the firing order over the engine, or bank of a V engine, some characteristics and how the engine design can influence them requires some more specific investigation. Understanding, on a fundamental level, the aspects of the engine design which influence these characteristics is critical to allow more detailed analysis and development work to be focused appropriately. The configuration of a Boxer engine gives a distinctive sound characteristic producing a unique sound compared to an In-Line configuration. Depending on the application it may be desirable to enhance or subdue some of these characteristics.
2016-06-15
Journal Article
2016-01-1774
Gert Herold, Thomas Geyer, Philipp Markus, Ennes Sarradj
Abstract The sound power level is the most important quantity that characterizes the noise emission of machinery. Following standardized procedures, it is usually calculated from sound pressure levels measured at a number of reference positions on a surface enveloping the object. The resulting value does not hold any direct information on the noise contributions of subcomponents. However, effective noise reduction necessitates a prior identification of acoustic sources and their characteristics. Combining the enveloping-surface method with microphone array measurements facilitates the evaluation of synchronously noise-emitting subcomponents. The application of this technique on a water pump with a four-stroke engine as power source is presented in this paper. The microphones are arranged on a cuboid surface surrounding the setup. The measured data is processed so as to yield sound power levels in a defined 3D focus region.
2016-06-15
Journal Article
2016-01-1778
Gesche Fender, Steffen Marburg, Fabian Duddeck
Abstract One method to lower noise in a cabin is to position damping layers on vibrating panels, thereby reducing their radiated power. To assess the damping effect, criteria like the ERP (equivalent radiated power) are widely employed, which estimate the radiated sound power of a panel without taking into account the actual complex system. Advantageously only a part of the structure has to be modeled, but the optimal solution found on the simplified model then often fails for the complete, coupled system, especially if several variants of a cabin have to be considered. Hence, it is proposed to use the structure-only optimization for identification of a set of candidate solutions for optimal positioning of damping layers. These candidate solutions used as initial designs for the coupled investigations should be well distributed in the design space to avoid being wrongly stuck in an optimum with inferior coupled performance.
2016-06-15
Journal Article
2016-01-1799
Corentin Chesnais, Nicolas Totaro, Jean-Hugh Thomas, Jean-Louis Guyader
Abstract The source field reconstruction aims at identifying the excitation field measuring the response of the system. In Near-field Acoustic Holography, the response of the system (the radiated acoustic pressure) is measured on a hologram using a microphones array and the source field (the acoustic velocity field) is reconstructed with a back-propagation technique performed in the wave number domain. The objective of the present works is to use such a technique to reconstruct displacement field on the whole surface of a plate by measuring vibrations on a one-dimensional holograms. This task is much more difficult in the vibratory domain because of the complexity of the equation of motion of the structure. The method presented here and called "Structural Holography" is particularly interesting when a direct measurement of the velocity field is not possible.
2016-06-15
Journal Article
2016-01-1801
Jonathan Vaudelle, Florian Godard, Florian Odelot, Anne Sanon
Abstract Acoustic comfort inside the vehicle is required whenever a wiper system is in function: front wiper motor noise is of great influence on the global comfort and its perception inside the car is 100% due to transmission of vibrations through wiper system fixation points on the vehicle. As any active source, both car manufacturer and system supplier need to be involved, at early stages of project development, in order to master the vibroacoustic integration of the system into the vehicle. This paper presents an experimental methodology dedicated to the front wiper system that offers the possibility to estimate the acoustic comfort inside the vehicle during project deployment phase, when modifications can still be proposed. Based on the XP-R-19701 standard, the procedure allows to measure, on a bench, the dynamic forces transmitted via the fixation points and details how to transpose them to the vehicle, taking into account the different specificities of the wiper system.
2016-06-15
Journal Article
2016-01-1808
Manfred Kaltenbacher, Andreas Hüppe, Aaron Reppenhagen, Matthias Tautz, Stefan Becker, Wolfram Kuehnel
Abstract We present a recently developed computational scheme for the numerical simulation of flow induced sound for rotating systems. Thereby, the flow is computed by scale resolving simulations using an arbitrary mesh interface scheme for connecting rotating and stationary domains. The acoustic field is modeled by a perturbation ansatz resulting in a convective wave equation based on the acoustic scalar potential and the substational time derivative of the incompressible flow pressure as a source term. We use the Finite-Element (FE) method for solving the convective wave equation and apply a Nitsche type mortaring at the interface between rotating and stationary domains. The whole scheme is applied to the numerical computation of a side channel blower.
2016-06-15
Journal Article
2016-01-1784
Alessandro Fortino, Lutz Eckstein, Jens Viehöfer, Jürgen Pampel
Abstract Vehicles powered by electric machines offer the advantage to be more silent than vehicles equipped with an internal combustion engine. On the one hand, the reduced noise levels enable an improvement of the inner-city noise pollution. On the other hand, quiet vehicles entail risks not to be acoustically detected by surrounding pedestrians and cyclists in the lower speed range. The emitted noise can easily be masked by the urban background noise. Therefore, the UNECE has founded an informal working group which is currently developing guidelines in terms of an exterior noise required for detecting Quiet Road Transport Vehicles (QRTV). With the introduction of an Acoustic Vehicle Alerting System (AVAS), not only the exterior noise but also the perceived interior noise for an enhanced driving experience can be considered. Nevertheless, car manufactures have a big interest in maintaining their perceived brand identity.
2016-06-15
Journal Article
2016-01-1809
Alexander Schell, Vincent Cotoni
Abstract Prediction of flow induced noise in the interior of a passenger car requires accurate representations of both fluctuating surface pressures across the exterior of the vehicle and efficient models of the vibro-acoustic transmission of these surface pressures to the driver’s ear. In this paper, aeroacoustic and vibro-acoustic methods are combined in order to perform an aero-vibro-acoustic analysis of a Mercedes-Benz A-class. The exterior aero-acoustic method consists of a time domain incompressible Detached Eddy Simulation (DES) and an acoustic wave equation. The method is extended in this paper to account for convection effects when modelling the exterior sound propagation. The interior vibro-acoustic model consists of a frequency domain Finite Element (FE) model of the side glass combined with a generalized Statistical Energy Analysis (SEA) model of the interior cabin.
2016-06-15
Journal Article
2016-01-1791
Noé F. Melo, Claus Claeys, Elke Deckers, Bert Pluymers, Wim Desmet
Abstract The NVH performance of conventional panels and structures is mainly driven by their mass. Silence often requires heavy constructions, which conflicts with the emerging trend towards lightweight design. To face the challenging and often conflicting task of merging NVH and lightweight requirements, novel low mass and compact volume NVH solutions are required. Vibro-acoustic metamaterials with stopband behavior come to the fore as possible novel NVH solutions combining lightweight requirements with superior noise and vibration insulation, be it at least in some targeted and tunable frequency ranges, referred to as stopbands. Metamaterials are artificial materials or structures engineered from conventional materials to exhibit some targeted performance that clearly exceeds that of conventional materials. They consist typically of (often periodic) assemblies of unit cells of non-homogeneous material composition and/or topology.
2016-06-15
Journal Article
2016-01-1788
Charles Pezerat
Abstract Identification of vibration sources, defects and/or material properties consists generally in solving inverse problems. The called RIFF method (French acronym meaning Windowed and Filtered Inverse Solving) is one way to solve this kind of inverse problem. The basic principle of the RIFF approach consists in measuring vibration displacement on a meshgrid in a local area of interest, injecting measured data in the motion equation and calculating the searched unknown. Compared to other usual inverse techniques, the RIFF method has the curious particularity of needing the knowledge of the local motion equation only. Boundary conditions, sources or dynamic behaviors outside the area of interest can be completely ignored, whereas they are required for the direct problem solving. The searched unknown can then be identified locally with respect to the frequency and can be mapped by using a scanning process of the area of interest.
2016-06-15
Journal Article
2016-01-1847
Olivier Robin, Celse Kafui Amedin, Alain Berry, Noureddine Atalla, Olivier Doutres, Franck Sgard
A method for estimating the sound absorption coefficient of a material under a synthesized Diffuse Acoustic Field was recently proposed, as an alternative to classical sound absorption measurements in reverberant rooms (Robin O., Berry A., Doutres O., Atalla N., ‘Measurement of the absorption coefficient of absorbing materials under a synthesized diffuse acoustic field’, J. Acoust. Soc. Am., 136 (1) EL13-EL19, 2014). Using sound field reproduction approaches and a synthetic array of acoustic monopoles facing the material, estimation of the sound absorption coefficient under a reproduced Diffuse Acoustic Field in a hemi-anechoic room was shown to be feasible. The method was successfully tested on a few samples of melamine foam of close thicknesses and areas, but the influence of several parameters such as the source height, or the samples dimensions together with the nature of the porous material was not fully investigated.
2016-06-15
Journal Article
2016-01-1795
Charly Faure, Charles Pezerat, Frédéric Ablitzer, Jérôme Antoni
In this paper, a local method of structure-borne noise source characterization is presented. It is based on measurements of transverse displacement and local structural operator knowledge and allows to localize and quantify sources without any need of boundary condition information. To fix the instability caused by measurement noise, the regularization step inherent to inverse problem is realized with a probabilistic approach, within the Bayesian framework. When a priori distributions about noise and sources are considered as Gaussian, the Bayesian regularization is equivalent to the well-known Tikhonov regularization. The optimization of the regularization is then performed by the Gibbs Sampling (GS) algorithm, which is part of Markov Chain Monte Carlo (MCMC) techniques. The whole probability of the regularized solution is inferred, providing access to confidence intervals.
2016-06-15
Journal Article
2016-01-1844
Jonathan Millitzer, Dirk Mayer, Roman Kraus, Matthias Schmidt
Abstract Current developments in the automotive industry such as downsizing, the use of cylinder deactivation and consistent lightweight construction increasingly enable the application of active control systems for the further reduction of noise and vibration in vehicles. In the past few years, different configurations of actuators and sensors for the realization of an active control system have been investigated and evaluated experimentally. Active engine mounts, inertial mass actuators and structural integrated actuators can be used to reduce either structural vibrations or the interior noise level. As a result, a variety of different topology concepts for the realization of an active control system arises. These can be divided into an active vibration control scenario, the direct influence of the sound field with loudspeakers or the application of structural actuators for the reduction of the interior sound pressure.
2016-06-15
Journal Article
2016-01-1817
Juergen Veit, Paco Langjahr, Stephan Brandl, Bernhard Graf
Abstract Due to more challenging future emission legislations and the trend towards downsizing, the number of turbocharged (TC) engines, especially petrol engines, is steadily increasing. The usage of TC has high risk to cause different noise phenomena apparent in the vehicle interior which are often perceived as annoying for the passengers. In order to further improve consideration of TC topics in the development, objective judgment and monitoring of TC noise issues is of high importance. Therefore, objective parameters and corresponding tools that are especially focusing on TC noise phenomena have to be developed. One main target of these tools is to deliver an objective TC assessment in an efficient way and with minimum additional effort. Application of the criteria presented in this publication therefore allows acoustic engineers to judge the NVH behavior and annoyance of the TC with respect to its vehicle interior noise contribution.
2016-06-15
Journal Article
2016-01-1827
Giorgio Bartolozzi, Marco Danti, Andrea Camia, Davide Vige
Abstract The time to market in the automotive industry is constantly decreasing pushing the carmaker companies to increase the efforts in numerical simulations and to decrease the number of prototypes. In the NVH field, this time constraint reflects in moving the well-established finite element simulations towards the so called “full-vehicle simulations”. Specifically, the CAE techniques should be able to predict the complete behavior of the vehicles in mission conditions, so to reproduce some usual tests, such as the “coast down” test on different roads. The aim of this paper is to present a methodology to improve rolling noise simulations exploiting an integrated full-vehicle approach. An accurate modeling of all the subsystems is needed, with particular attention to the wheels and the suspension systems. Therefore, the paper firstly covers the modeling approach used to obtain the FE models of tires and suspension system.
2016-06-15
Journal Article
2016-01-1825
Jung-Han Woo, Da-Young Kim, Jeong-Guon Ih
Abstract To hear the powerful and spectrally rich sound in a car is costly, because the usual car audio system adopts small loudspeakers. Also, the available positions of the loudspeakers are limited, that may cause the reactive effect from the backing cavity and the sound distortion. In this work, a part of the roof panel of a passenger car is controlled by array actuators to convert the specified large area to be a woofer. An analogous concept of the acoustic holography is employed to be projected as the basic concept of an inverse rendering for achieving a desired vibration field. The vibration of the radiating zone is controlled to be in a uniform phase, and the other parts outside it are to be made a no-change zone in vibration. The latter becomes a baffle for the woofer, and the backing cavity is virtually infinite if the sound radiation into the passenger cabin is only of concern.
2016-06-15
Journal Article
2016-01-1777
Sebastian Oberst, Zhi Zhang, Joseph CS Lai
Abstract Despite significant progress made in the past 20 years in discovering some of the mechanisms of brake squeal, it remains difficult to predict the underlying friction-induced instabilities reliably. Most numerical analyses are based on linear deterministic analyses of structural vibrations such as the complex eigenvalue analysis (CEA). However, nonlinear multi-scale processes govern friction contact with high sensitivities to operating and/or environmental conditions. In addition, uncertainties in the material properties and boundary conditions such as contact and friction laws are rarely considered. Hence, it is quite common to underpredict or overpredict the number of instabilities and extensive brake noise dynamometer tests are still required in industry to ensure acceptable brake noise performance. In this paper, simplified finite element brake models are used to illustrate the role of nonlinearity in brake squeal.
2016-06-15
Journal Article
2016-01-1819
Antonio J. Torregrosa, Alberto Broatch, Vincent Raimbault, Jerome Migaud
Abstract Intake noise has become one the main concerns in the design of highly-supercharged downsized engines, which are expected to play a significant role in the upcoming years. Apart from the low frequencies associated with engine breathing, in these engines other frequency bands are also relevant which are related to the turbocharger operation, and which may radiate from the high-pressure side from the compressor outlet to the charge air cooler. Medium frequencies may be controlled with the use of different typologies of resonators, but these are not so effective for relatively high frequencies. In this paper, the potential of the use of multi-layer porous materials to control those high frequencies is explored. The material sheets are located in the side chamber of an otherwise conventional resonator, thus providing a compact, lightweight and convenient arrangement.
2016-06-15
Journal Article
2016-01-1855
Alastair Jay, Thomas Deighan, Nozomu Kato, Kiyofumi Sato
Abstract Requirements for reducing powertrain NVH drives the selection of low piston skirt to liner clearances contradicting the requirement to maintain larger skirt clearances for minimizing engine friction. Whilst this clearance trade-off between low friction and low NVH is fundamental, piston design features have a significant effect on where the trade-off curve sits on the friction/NVH map. Design features can therefore be viewed not by either friction or NVH improvement measures but a shift in the friction-NVH trade off curve. Specifically, some piston design features which may be targeted at reducing friction can be viewed as either a friction benefit for similar NVH or an NVH improvement for similar friction levels. The ability to realistically quantify the effect of the design changes on NVH is therefore critical to determining what design changes to recommend, the direction of the piston design being highly sensitive to the process by which the impact on NVH is assessed.
2016-06-15
Technical Paper
2016-01-1834
Florian Fink, Gregor Koners
Abstract This paper describes the prediction process of wheel forces and moments via indirect transfer path analysis, followed by an analysis of the influence of wheel variants and suspension modifications. It proposes a method to calculate transmission of noise to the vehicle interior where wheel forces and especially moments were taken into account. The calculation is based on an indirect transfer path analysis with geometrical modifications of the frequency response functions. To generate high quality broadband results, this paper also points out some of the main clearance cutting criteria. The method has been successfully implemented to show the influence of wheel tire combinations as well as the influence of suspension modifications. Case studies have been performed and will be presented in this paper. Operational noise and vibration measurements have been carried out on Daimler NVH test tracks. The frequency response functions were estimated in an acoustic laboratory.
2016-06-15
Technical Paper
2016-01-1787
Thomas Deighan, Graeme Maclean, Nozomu Kato, Kiyofumi Sato
Abstract A robust analytical process for evaluating the effects of engine component design on the powertrain NVH has been developed. The work presented focuses on design modifications for refinement of the NVH levels and sound quality of a 4 cylinder Boxer engine with automatic transmission. Assessment focuses on the powertrain structure, cranktrain, torque converter and valvetrain. Comparison of predicted mount vibrations with measurements on a fired engine are made. Through detailed post-processing of the analysis results, looking at modal contributions, modal excitations and loading contributions, the causes and contributions to the NVH are understood and used to direct potential modifications to the powertrain and component design. The models are used to quantify the relative benefit of these modifications in terms of both overall vibration levels and sound quality through implementation of a rumble metric.
2016-06-15
Journal Article
2016-01-1815
Augusto Della Torre, Gianluca Montenegro, Angelo Onorati
Abstract In the last decades numerical simulations have become reliable tools for the design and the optimization of silencers for internal combustion engines. Different approaches, ranging from simple 1D models to detailed 3D models, are nowadays commonly applied in the engine development process, with the aim to predict the acoustic behavior of intake and exhaust systems. However, the acoustic analysis is usually performed under the hypothesis of infinite stiffness of the silencer walls. This assumption, which can be regarded as reasonable for most of the applications, can lose validity if low wall thickness are considered. This consideration is even more significant if the recent trends in the automotive industry are taken into account: in fact, the increasing attention to the weight of the vehicle has lead to a general reduction of the thickness of the metal sheets, due also to the adoption of high-strength steels, making the vibration of the components a non negligible issue.
2016-06-15
Technical Paper
2016-01-1854
Johannes Seifriedsberger, Rudolf Wichtl, Helmut Eichlseder
Abstract The present article is concerned with the investigation of the engine noise induced by the piston slap of an actual passenger car Diesel engine. The focus is put on the coherence of piston secondary movement, impact of the piston on the cylinder liner, generated structure-borne noise excitation of the engine structure and the occurring acceleration on the engine surface. Additionally, the influence of a varying piston-pin offset and piston clearance is evaluated. The analyses are conducted using an elastohydrodynamic multi-body simulation model, taking into account geometry, stiffness and mass information of the single components as well as considering elastic and hydrodynamic behavior of the piston-liner contact. A detailed description of the simulation model will be introduced in the article. The obtained results illustrate the piston secondary motion and the related structure-borne noise on the engine surface for several piston-pin offsets and piston clearances.
2016-05-11
Technical Paper
2016-36-0061
Juliana Negrini de Araújo, Leonardo Hoss, Alexandre Viecelli, Maicon Molon
Abstract The use of virtual and / or experimental test rigs applying random loading is becoming more relevant in the development and validation of new products. An application example is the analysis of components subject to vibrations, especially suspended components. For this type of application, product validation applying random loads and different frequencies becomes mandatory. This study developed a virtual test rig for suspended components validation and definition of experimental test rigs. The study was based on a standard component, using LMS Virtual.Lab Siemens software for the dynamic analysis and durability. The experimental data (extensometry and accelerometry) was collected on the special tracks of Randon Companies Proving Ground. From the virtual modeling and experimental data, the proper hydraulic actuators signals were defined to characterize the component behavior according to the field application.
2016-05-11
Technical Paper
2016-36-0067
Gustavo de Godoy José, Mauro Rebelatto, Rui Gustavo Lippert Schwanke, Telmo Roberto Strohaecker
Abstract This paper presents several tests carried out on a truck trailer on different types of pavement and load condition, using proving ground tracks and facilities, the instrumentation details, data analysis and validation. Through an extensive analysis of Brazilian goods road transport, a load vehicle combination and a list of test pavements were chosen as off-road pavement, highway pavement, pot holes, washboard, cobblestones and Belgian blocks. Accelerometers were installed throughout the truck trailer chassis longitudinal length in order to obtain the acceleration levels and vibration frequencies on the truck trailer sprung mass. Aiming to evaluate the base excitation imposed to parts mounted to the truck trailers chassis, according to their mounting position, data processing method and cutoff frequency definition strategies were defined.
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