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2016-06-15
Technical Paper
2016-01-1793
Sandra Forget, Nicolas Totaro, Jean-Louis Guyader, Michel Schaeffer
Abstract The constant evolution in the automotive sector to achieve more eco-friendly vehicles has induced the development of more efficient systems with new components and innovative materials. To evaluate the impact of these technologies or to improve them in terms of NVH performances, acoustic engineers rely on experimental tests and numerical computations. In this context, the use of experimental noise sources identification and characterization methods can provide interesting approaches. However, classical methods usually used in industry like the Nearfield Acoustical Holography (NAH) or the Beamforming techniques are quickly limited, in particular in terms of precision in localization, for such analysis support. The presented method, named M-iPTF for Mixed inverse Patch Transfer Functions, is more suitable as it is able to localize and quantify all acoustic source fields directly on the real geometry of a complex structure.
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
2016-01-1807
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
2016-01-1804
Stefan Becker, Katrin Nusser, Marco Oswald
Abstract Aim of the ongoing development of passenger cars is to predict the interior acoustics early in the development process. A significant noise component results from the flow phenomena in the area of the side window. Wind noise is a physical problem that involves the three complicated aspects each governed by different physics: The complex turbulent flow field in the wake of the a-pillar and the side mirror is characterized by velocity and pressure fluctuations. The flow field generates sound which is transmitted into the passenger cabin. In addition to that, it excites the structure, resulting in a radiation of structure-borne noise into the interior of the car. Therefore, the sound generation is governed by fluid dynamics of the air flow. The sound transmission through the structure due to vibrations is determined by structural mechanics of the body structure. The sound propagation inside the cabin is influenced by interior room acoustics.
2016-06-15
Technical Paper
2016-01-1806
Sumon Sinha, Farokh Kavarana, Dan Williams, Kazuya Asao
Abstract A high performance rigid airfoil profile sunroof wind deflector has been developed for high speed freeway driving with the sunroof open. This deflector is clearly superior to the conventional bar type deflector and less expensive compared to tall flexible fabric mesh deflectors applied on high end vehicles today. It provides superior speech intelligibility under high speed driving with sunroof open. The criterion for designing this deflector was to get the highest airspeed possible to span the sunroof opening under all conditions. The customized shape also utilizes flow unsteadiness, including those at the onset of buffeting, in order to condition the shear layer. The airfoil profiled deflector yielded superior mid and high frequency acoustic performance with acceptable low frequency performance. A shorter airfoil deflector was sufficient to keep the external airflow from entering the forward tilted sunroof opening on a mid-size SUV under test.
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
Technical Paper
2016-01-1800
Xavier Carniel, Anne Sanon
Abstract The control of sound fields radiated by vibrating structures in a passenger compartment, (especially structures connected to different organs like the engine powertrain, the fan motor unit, seats, the steering column, electrical motors more and more, etc.) is among the functions of the automotive manufacturers. The absence of physical prototypes in the development phase systems led OEMs1 to use tests results obtained on benches following technical specifications from manufacturers. The transition "bench to vehicle" for vibro- acoustic behaviour sets many challenges that this standard intends to clear up. This standard specifies the experimental method to transpose the dynamic forces generated by the global movements of an active component between the vehicle and a test bench. The efforts are first measured on test benches and then transposed from test bench towards the vehicle. The standard is now a French standard (XP R 19-701) and is submitted to ISO process [1].
2016-06-15
Technical Paper
2016-01-1803
Hannes Frank, Claus-Dieter Munz
Avoiding narrowband components in the acoustic spectrum is one of the most critical objectives in the automotive aeroacoustic optimization process. The underlying physical mechanisms are not completely understood. In a preceding numerical and experimental investigation, we performed large eddy simulations of an early-development stage realistic side-view mirror, where tonal noise was captured and the principle mechanisms were identified. In this contribution, we present simulations on a simplified two-dimensional geometry that is based on these findings. It is shown that the basic flow topology relevant for tonal noise generation on the original side-view mirror as well as the tonal noise source is reproduced in the 2D case. Furthermore, we present comparisons with measurements and the necessity and influence of a splitter plate downstream of the 2D body to avoid large scale vortex shedding.
2016-06-15
Technical Paper
2016-01-1802
Mehdi Mehrgou, Franz Zieher, Christoph Priestner
Abstract Recently, hybrid and fully electric drives have been developing widely in variety, power and range. The new reliable simulation approaches are needed, in order to meet the defined NVH targets of these systems and implementing CAE methods for front loading, Design Validation Process (DVP). This paper introduces the application of a novel NVH analysis workflow on an electric vehicle driveline including both electromagnetic and mechanical excitations for an absolute evaluation of the NVH performance. At first, the electromagnetic field is simulated using FEM method to extract the excitations on the stator, rotor bearings as well as the drive torque. Then, the multibody dynamic model of the driveline is built-up, driven by this torque. The effect of eccentricity and skew angle of rotor in electromagnetic excitations are shown.
2016-06-15
Technical Paper
2016-01-1814
Maxime Legros, Jean Michel Ville, Solène Moreau, Xavier Carniel, Christophe Lambourg, Guillaume Stempfel
Abstract The new requirements during the first stages of the conception of a HVAC prompt the designer to integrate the acoustic problematic increasingly upstream. The designer needs to select a coherent components’ choice in order to comply with the specifications in terms of aeraulic and acoustic performances. A tool has been created to guide the designer’s choices based on an acoustic synthesis which is a design and/or diagnosis approach used to analyze and predict the acoustic behavior of a complex system. The synthesis is developed in order to propose an approach which considers the integration effects and some interaction effects. The acoustic synthesis results are the starting point of a psycho-acoustic study providing audio samples of the prediction and indications of the HVAC acceptance by the prospective user. Also, one may compare the results of different acoustic synthesis projects to study the influence of the parameters on the acoustic prediction.
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
2016-01-1812
Saad Bennouna, Solène Moreau, Jean Michel Ville, Olivier Cheriaux
Abstract The noise radiated inside the car cabin depends on many sources such as the embedded equipments like the Heating, Ventilation and Air Conditioning (HVAC) module. An HVAC is a compact and complex system composed of several elements: blower, flaps, thermal exchangers, ducts… Air provided by an HVAC is blown by a blower passing through different components and then distributed to car cabin areas. Interactions between airflow and the HVAC fixed components generate noises that emerge in the car cabin. CEVAS project, managed by the automotive equipment manufacturer Valeo, is aiming to develop a prediction tool which will provide HVAC noise spectrum and sound quality data. The tool is based, in particular, on aeroacoustic characterization of individual elements and associations of elements.
2016-06-15
Technical Paper
2016-01-1813
Daniela Siano, Fabio Bozza
Abstract The characteristics of the intake system affect both engine power output and gas-dynamic noise emissions. The latter is particularly true in downsized VVA engines, where a less effective attenuation of the pressure waves is realized, due to the intake line de-throttling at part-load. For this engine architecture, a refined air-box design is hence requested. In this work, the Transmission Loss (TL) of the intake air-box of a commercial VVA engine is numerically computed through a 3D FEM approach. Results are compared with experimental data, showing a very good correlation. The validated model is then coupled to an external optimizer (ModeFRONTIERTM) to increase the TL parameter in a prefixed frequency range. The improvement of the acoustic attenuation is attained through a shape deformation of the inner structure of the base device, taking into account constraints related to the device installation inside the engine bay.
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
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
2016-01-1809
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
Technical Paper
2016-01-1822
Drasko Masovic, Franz Zotter, Eugene Nijman, Jan Rejlek, Robert Höldrich
Abstract Radiation of sound from an open pipe with a hot mean flow presents one of the classic problems of acoustics in inhomogeneous media. The problem has been especially brought into focus in the last several decades, in the context of noise control of vehicle exhaust systems and jet engines. However, the reports on the measurements of the radiated sound field are still rare and scattered over different values of subsonic and supersonic flow speeds, cold and hot jets, as well as different sound frequency ranges. This paper focuses on low Mach number values of the mean flow speed and low frequencies of the incident (plane) sound waves inside an unflanged cylindrical pipe with a straight cut. It presents the results of the far-field radiation pattern measurements and compares them with an existing analytical model from the literature. The mean flow inside the pipe reached Mach number values up to 0.25 and temperature up to 300°C.
2016-06-15
Technical Paper
2016-01-1821
Lin Du, Mats Abom, Mikael Karlsson, Magnus Knutsson
Abstract To tune the acoustics of intake systems resonators are often used. A problem with this solution is that the performance of these resonators can be affected a lot by flow. First, for low frequencies (Strouhal-numbers) the acoustic induced vorticity across a resonator inlet opening will create damping, which can reduce the efficiency. Secondly, the vorticity across the opening can also change the end-correction (added mass) for the resonator, which can modify the resonance frequency. However, the largest problem that can occur is whistling. This happens since the vortex-sound interaction across a resonator opening for certain Strouhal-numbers will amplify incoming sound waves. A whistling can then be created if this amplified sound forms a feedback loop, e.g., via reflections from system boundaries or the resonator. To analyse this kind of problem it is necessary to have a model that allows for both sound and vorticity and their interaction.
2016-06-15
Technical Paper
2016-01-1820
Mikael Karlsson, Magnus Knutsson, Mats Abom
Abstract This work explores how fluid driven whistles in complex automotive intake and exhaust systems can be predicted using computationally affordable tools. Whistles associated with unsteady shear layers (created over for example side branches or perforates in resonators) are studied using vortex sound theory; vorticity in the shear layer interacts with the acoustic field while being convected across the orifice. If the travel time of a hydrodynamic disturbance over the orifice reasonably matches a multiple of the acoustic period of an acoustic feedback system, energy is transferred from the flow field to the acoustic field resulting in a whistle. The actual amplitude of the whistle is set by non-linear saturation phenomena and cannot be predicted here, but the frequency and relative strength can be found. For this not only the mean flow and acoustic fields needs to be characterized separately, but also the interaction of the two.
2016-06-15
Technical Paper
2016-01-1818
Raimo Kabral, Lin Du, Mats Abom, Magnus Knutsson
Abstract The concept of IC engine downsizing is a well-adapted industry standard, enabling better fuel conversion efficiency and the reduction of tailpipe emissions. This is achieved by utilizing different type of superchargers. As a consequence, the additional charger noise emission, at the IC engine inlet, can become a problem. In order to address such problem, the authors of this work have recently proposed a novel dissipative silencer for effective and robust noise control of the compressor. Essentially, it realizes an optimal flow channel impedance, referred to as the Cremer impedance. This is achieved by means of a straight flow channel with a locally reacting wall consisting of air cavities covered by an acoustic resistance, e.g., a micro-perforated panel (MPP). In this paper, an improved optimization method of this silencer is presented. The classical Cremer impedance model is modified to account for mean flow dependence of the optimal wave number.
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
2016-01-1817
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
Technical Paper
2016-01-1816
Heiki Tiikoja, Fabio Auriemma, Jüri Lavrentjev
Abstract In this paper the propagation of acoustic plane waves in turbulent, fully developed flow is studied by means of an experimental investigation carried out in a straight, smooth-walled duct. The presence of a coherent perturbation, such as an acoustic wave in a turbulent confined flow, generates the oscillation of the wall shear stress. In this circumstance a shear wave is excited and superimposed on the sound wave. The turbulent shear stress is modulated by the shear wave and the wall shear stress is strongly affected by the turbulence. From the experimental point of view, it results in a measured damping strictly connected to the ratio between the thickness of the acoustic sublayer, which is frequency dependent, and the thickness of the viscous sublayer of the turbulent mean flow, the last one being dependent on the Mach number. By reducing the turbulence, the viscous sublayer thickness increases and the wave propagation is mainly dominated by convective effects.
2016-06-15
Technical Paper
2016-01-1836
Sylvestre Lecuru, Pascal Bouvet, Jean-Louis Jouvray, Shanjin Wang
Abstract The recent use of electric motors for vehicle propulsion has stimulated the development of numerical methodologies to predict their noise and vibration behavior. These simulations generally use models based on an ideal electric motor. But sometimes acceleration and noise measurements on electric motors show unexpected harmonics that can generate acoustic issues. These harmonics are mainly due to the deviation of the manufactured parts from the nominal dimensions of the ideal machine. The rotor eccentricities are one of these deviations with an impact on acoustics of electric motors. Thus, the measurement of the rotor eccentricity becomes relevant to understand the phenomenon, quantify the deviation and then to use this data as an input in the numerical models. An innovative measurement method of rotor eccentricities using fiber optic displacement sensors is proposed.
2016-06-15
Technical Paper
2016-01-1835
Albert Albers, Fabian Schille, Matthias Behrendt
Abstract In terms of customer requirements, driving comfort is an important evaluation criterion. Regarding hybrid electric vehicles (HEVs), maneuver-based measurements are necessary to analyze this comfort characteristic [1]. Such measurements can be performed on acoustic roller test benches, yielding time efficient and reproducible results. Due to full hybrid vehicles’ various operation modes, new noise and vibration phenomena can occur. The Noise Vibration Harshness (NVH) performance of such vehicles can be influenced by transient powertrain vibrations e.g. by the starting and stopping of the internal combustion engine in different driving conditions. The paper at hand shows a methodical procedure to measure and analyze the NVH of HEVs in different driving conditions.
2016-06-15
Technical Paper
2016-01-1832
Ramakrishna Kamath
Intermediate shaft assembly is used to connect steering gear to the steering wheel. The primary function of the intermediate shaft is to transfer torsional loads. There is a high probability of noise propagating through the Intermediate shaft to the driver. The current standard for measuring the noise is by performing vehicle level subjective evaluations. If improperly clamped at either of the yokes, a sudden change in the direction of the torsional load on the Intermediate shaft can generate a displeasing noise. Noise can also be generated from the constant velocity joint. Intermediate shaft noise can be measured using a microphone or can be correlated to acceleration values. The benefit of measuring the acceleration over sound pressure level is the reduction of complexity of the test environment and test set up. The nature of the noise in question requires the filtering of low frequency data. This paper presents a new test procedure that has been developed by General Motors.
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
2016-01-1830
Denis Blanchet, Luca Alimonti, Anton Golota
Abstract This paper presents new advances in predicting wind noise contribution to interior SPL in the framework of the Wind Noise German Working Group composed of Audi, Daimler, Porsche and VW. In particular, a new approach was developed that allows to fully describe the wind noise source using CFD generated surface pressure distribution and its cross-correlation function and apply this source on an SEA side glass. This new method removes the need to use a diffuse acoustic field or several plane waves with various incidence angle to approximate the correct acoustics source character to apply on the SEA side glass. This new approach results are compared with results previously published which use more deterministic methods to represent the side glass and the interior of a vehicle.
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.
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