A Computational Fluid Dynamics Model for Investigating Air-Pumping Mechanisms in Air-Borne Tire Noise

2016 ◽  
Vol 44 (3) ◽  
pp. 191-211 ◽  
Author(s):  
Prashanta Gautam ◽  
Abhilash J. Chandy
Keyword(s):  
Stokes Equations ◽  
Road Traffic ◽  
Near Field ◽  
Spectral Characteristics ◽  
Small Scale ◽  
Road Traffic Noise ◽  
Far Field ◽  
Noise Generation ◽  
Tire Noise ◽  
Noise Characteristics

ABSTRACT The reduction in power train noise over the past decade has led to an increased focus in reducing tire/road noise, largely due to the environmental concerns related to road traffic noise in industrial countries. Computational fluid dynamic (CFD) simulations conducted using ANSYS FLUENT are presented here with the objective of understanding air-pumping noise-generation mechanisms due to tire/road interaction. The CFD model employs a large eddy simulation turbulence modeling approach, in which the filtered compressible Navier-Stokes equations are solved to obtain temporally and spatially accurate near-field pressure fluctuations for a two-dimensional (2D) tire geometry with (1) one groove and (2) two grooves. In addition, the Ffowcs-Williams and Hawkings (FW-H) acoustic model is used to predict far-field acoustics. The deformation of the grooves, as the tire rotates, is represented by prescribed sidewall movements. Consequently, the solution to the numerical problem is obtained through a single process, thereby enabling the prediction of small-scale air pumping, horn effect, and far-field acoustics in a single simulation. The acoustic characteristics associated with air pumping are studied through spectral analysis tools, and comparisons show that the additional groove on the horn geometry alters the spectral characteristics of air pumping. Validation of the model is conducted through qualitative and quantitative comparisons with previous studies. These simulations are intended to provide a deeper understanding about the small-scale noise generation as well as the near-field and far-field acoustics, thereby paving the way for the automotive manufacturer to compare a variety of air-related tire noise characteristics without spending time and money for vehicle pass-by tests.

Understanding Tire Acoustics Through Computational Fluid Dynamics (CFD) of Grooves With Deforming Walls

2015 ◽  
Author(s):  
Prashanta Gautam ◽  
Abhilash J. Chandy
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Stokes Equations ◽  
Road Traffic ◽  
Small Scale ◽  
Road Traffic Noise ◽  
Noise Generation ◽  
Cfd Model ◽  
Computational Fluid Dynamics Cfd ◽  
Generation Mechanisms

Reducing tire noise has been a topic of increased focus in the recent years in industrial countries in order to decrease road traffic noise. Computational fluid dynamics (CFD) simulations conducted using ANSYS FLUENT are presented here to provide a better understanding of the small-scale noise generation mechanisms due to air-pumping at the tire-road interface. The CFD model employs a large eddy simulation (LES) turbulence modeling approach, where the filtered compressible Navier-Stokes equations are solved for simple groove geometries with a moving bottom wall that represents the deformation due to the tire movement along the road surface. A horizontally moving wall is used to represent the motion of the tire groove in and out of the contact patch while the deformation of the groove is prescribed. Temporal and spatially accurate pressure fluctuations are utilized to determine sound pressure levels and dominant frequencies. In addition to an understanding of noise generation mechanisms in such grooves, the CFD model developed here can potentially provide a series of control parameters that can help optimize the tire performance in terms of tire acoustics.

WAVELET-BASED POSTPROCESSING OF JET LES DATA FOR ACOUSTIC FAR-FIELD EXTRAPOLATIONS

2013 ◽  
Vol 21 (04) ◽  
pp. 1350017
Author(s):  
RAMIN KAVIANI ◽  
VAHID ESFAHANIAN ◽  
MOHAMMAD EBRAHIMI
Keyword(s):  
Large Scale ◽  
Stokes Equations ◽  
Near Field ◽  
Flow Simulation ◽  
Computational Time ◽  
Jet Flows ◽  
Small Scale ◽  
Frequency Noise ◽  
Far Field ◽  
Noise Sources

The affordable grid resolutions in conventional large-eddy simulations (LESs) of high Reynolds jet flows are unable to capture the sound generated by fluid motions near and beyond the grid cut-off scale. As a result, the frequency spectrum of the extrapolated sound field is artificially truncated at high frequencies. In this paper, a new method is proposed to account for the high frequency noise sources beyond the resolution of a compressible flow simulation. The large-scale turbulent structures as dominant radiators of sound are captured in LES, satisfying filtered Navier–Stokes equations, while for small-scale turbulence, a Kolmogorov's turbulence spectrum is imposed. The latter is performed via a wavelet-based extrapolation to add randomly generated small-scale noise sources to the LES near-field data. Further, the vorticity and instability waves are filtered out via a passive wavelet-based masking and the whole spectrum of filtered data are captured on a Ffowcs-Williams/Hawkings (FW-H) surface surrounding the near-field region and are projected to acoustic far-field. The algorithm can be implemented as a separate postprocessing stage and it is observed that the computational time is considerably reduced utilizing a hybrid of many-core and multi-core framework, i.e. MPI-CUDA programming. The comparison of the results obtained from this procedure and those from experiments for high subsonic and transonic jets, shows that the far-field noise spectrum agree well up to 2 times of the grid cut-off frequency.

ANALYSIS OF A HETEROGENEOUS DOMAIN DECOMPOSITION FOR COMPRESSIBLE VISCOUS FLOW

2001 ◽  
Vol 11 (04) ◽  
pp. 565-599 ◽  
Author(s):  
CRISTIAN A. COCLICI ◽  
WOLFGANG L. WENDLAND
Keyword(s):  
Domain Decomposition ◽  
Stokes Equations ◽  
Domain Decomposition Method ◽  
Near Field ◽  
Outer Region ◽  
Navier Stokes ◽  
Far Field ◽  
Computational Domain ◽  
Linearized Euler Equations ◽  
Naca0012 Airfoil

We analyze a nonoverlapping domain decomposition method for the treatment of two-dimensional compressible viscous flows around airfoils. Since at some distance to the given profile the inertial forces are strongly dominant, there the viscosity effects are neglected and the flow is assumed to be inviscid. Accordingly, we consider a decomposition of the original flow field into a bounded computational domain (near field) and a complementary outer region (far field). The compressible Navier–Stokes equations are used close to the profile and are coupled with the linearized Euler equations in the far field by appropriate transmission conditions, according to the physical properties and the mathematical type of the corresponding partial differential equations. We present some results of flow around the NACA0012 airfoil and develop an a posteriori analysis of the approximate solution, showing that conservation of mass, momentum and energy are asymptotically attained with the linear model in the far field.

scholarly journals Sound generation in a mixing layer

1997 ◽  
Vol 330 ◽  
pp. 375-409 ◽  
Author(s):  
TIM COLONIUS ◽  
SANJIVA K. LELE ◽  
PARVIZ MOIN
Keyword(s):  
Acoustic Field ◽  
Stokes Equations ◽  
Near Field ◽  
Mixing Layer ◽  
Navier Stokes ◽  
Far Field ◽  
Source Terms ◽  
Acoustic Analogy ◽  
Navier Stokes Equations ◽  
Acoustic Sources

The sound generated by vortex pairing in a two-dimensional compressible mixing layer is investigated. Direct numerical simulations (DNS) of the Navier–Stokes equations are used to compute both the near-field region and a portion of the acoustic field. The acoustic analogy due to Lilley (1974) is also solved with acoustic sources determined from the near-field data of the DNS. It is shown that several commonly made simplifications to the acoustic sources can lead to erroneous predictions for the acoustic field. Predictions based on the quadrupole form of the source terms derived by Goldstein (1976a, 1984) are in excellent agreement with the acoustic field from the DNS. However, despite the low Mach number of the flow, the acoustic far field generated by the vortex pairings cannot be described by considering compact quadrupole sources. The acoustic sources have the form of modulated wave packets and the acoustic far field is described by a superdirective model (Crighton & Huerre 1990). The presence of flow–acoustic interactions in the computed source terms causes the acoustic field predicted by the acoustic analogy to be very sensitive to small changes in the description of the source.

Tensor CSAMT survey over the Sulphur Springs thermal area, Valles Caldera, New Mexico, United States of America, Part II: Implications for CSAMT methodology

Geophysics ◽  
1997 ◽  
Vol 62 (2) ◽  
pp. 466-476 ◽  
Author(s):  
Philip E. Wannamaker
Keyword(s):  
Near Field ◽  
Skin Depth ◽  
Small Scale ◽  
Far Field ◽  
Survey Area ◽  
Wave Regime ◽  
Low Frequencies ◽  
Field Source ◽  
Source Field ◽  
Sulphur Springs

The resistivity model for the Sulphur Springs area in the companion paper (Part I) plus the availability of overlapping controlled‐source audiomagnetotelluric (CSAMT) and magnetotelluric (MT) data has allowed study of far‐field to near‐field transitions, source field geometries over the survey area, and scalar‐tensor impedance discrepancies. The regional setting of conductive Paleozoic sediments over resistive basement seriously reduced depth of exploration within the plane‐wave regime to about 1/20th of the transmitter‐receiver separation, rather than the traditional 1/3rd to 1/5th based on half‐space models. As frequency falls to where skin depth in the sedimentary layer exceeds its thickness, transmitter electromagnetic (EM) fields enter the resistive basement and may diffuse to the receiver with relatively little attenuation, promoting near‐field behavior. Comparisons are made of observed electric (E) and magnetic (H) fields inside and outside the caldera with EM fields computed from layered resistivity models derived from local 1-D inversion of the ρa and θ, and from simple 3-D models. First, the comparisons indicate that small‐scale structure near the transmitter does not lead to overprint effects in the impedance data at the receiver but, instead, acts as an equivalent far‐field source. Second, at both high and low frequencies, the observed E and H fields can depart substantially from those predicted by local layered models. In fact, an effective regional layering appears to control the magnetic field amplitudes and the far‐to near‐field transition in this survey area. The observed electric fields, on the other hand, are controlled by all scales of geology. When heterogeneity is important, significant departures between scalar and tensor CSAMT data can be expected, and are exacerbated when the source field is poorly coupled to the sensors. The problem is much reduced for vector CSAMT measurements where all horizontal field components are measured and the maximally coupled results are defined, but mode identification is more difficult for multidimensional structures.

Dynamics of an impinging jet. Part 2. The noise generation

1982 ◽  
Vol 116 ◽  
pp. 379-391 ◽  
Author(s):  
Nagy S. Nosseir ◽  
Chih-Ming Ho
Keyword(s):  
Coherent Structures ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Aerodynamic Noise ◽  
Far Field ◽  
Noise Generation ◽  
Physical Mechanisms ◽  
Field Noise ◽  
Subsonic Jet ◽  
Jet Axis

The aerodynamic noise generated by a subsonic jet impinging on a flat plate is studied from measurements of near-field and surface-pressure fluctuations. The far-field noise measured at 90° to the jet axis is found to be generated by two different physical mechanisms. One mechanism is the impinging of the large coherent structures on the plate, and the other is associated with the initial instability of the shear layer. These two sources of noise radiate to the far field via different acoustical paths.

The Generation and Propagation of Ship Internal Waves in a Generally Stratified Ocean at High Densimetric Froude Numbers, Including Nonlinear Effects

2000 ◽  
Vol 44 (03) ◽  
pp. 197-227
Author(s):  
Marshall P. Tulin ◽  
Yitao Yao ◽  
Pei Wang
Keyword(s):  
Internal Wave ◽  
Internal Waves ◽  
Near Field ◽  
Nonlinear Effects ◽  
Wave Pattern ◽  
Small Scale ◽  
Far Field ◽  
Asymptotic Equation ◽  
Densimetric Froude Number ◽  
Central Lobe

A nonlinear theory for internal wave generation and propagation is derived here for slender ships traveling at high densimetric Froude number (Fh >> 1) in water of small density variation. It is based on an asymptotic equation for the evolution of the internal wave vorticity generated under the ship by a known inviscid ship flow and then self-propagating in the wake. In its numerical implementation, arbitrary pycnoclines and slender ship hulls may be used, and boundary conditions on the ship hull are satisfied; the free surface is treated here as rigid, although this may be relaxed. The theory has been implemented by a suitable numerical method and numerous simulations have been carried out. The results have been compared with earlier OEL experiments. In the near field, emphasis is given to a triple-lobe pattern in the pycnocline, an upwelling along the centerline of motion with a trough on either side, forming close behind the ship. Two distinct types of triple lobes are identified:dominant central lobe and very weak troughs, and;weak central lobe and dominant troughs. The former (a) is shown to result in linear propagation into the far field. The latter (b) results in far-field patterns preceded by a deep trough whose propagation is nonlinear. The comparisons of both simulated trends and actual amplitudes with measurements are good, surprisingly so considering the small scale of the experiment and the asymptotic nature of the theory. The effect of the turbulent wake on the internal waves in the experiments is restricted to a very narrow region behind the ship; the bulk of the wave pattern including the leading waves seem unaffected. Simulations show that under certain conditions of stratification, triple-lobe patterns with abnormally large troughs are generated and lead to strong nonlinear effects; these deep troughs propagate sidewards to large distances aft (over 40 ship lengths) with slow decay, and result in much larger surface currents and strain rates than in the normal case. Correspondingly, fast waves of depression, which decay slowly, were discovered through the simulation of two-dimensional initial value problems, where the initial area of depression was significantly less than required of a true soliton; these "quasi-solitons" are briefly studied here.

An experimental and computational investigation of air-borne noise generation mechanisms in tires

2018 ◽  
Vol 25 (3) ◽  
pp. 529-537 ◽  
Author(s):  
Prashanta Gautam ◽  
Yousof Azizi ◽  
Abhilash J. Chandy
Keyword(s):  
Spectral Characteristics ◽  
Operating Conditions ◽  
Complex Nature ◽  
Generation Process ◽  
Noise Generation ◽  
Frequency Spectra ◽  
Tire Noise ◽  
Noise Data ◽  
Generation Mechanisms ◽  
Air Pockets

The complex nature of the tire/road noise generation process makes it difficult to isolate and study each mechanism individually. This paper presents an experimental and numerical investigation of air-borne tire noise generation mechanisms for a realistic tire. Experimentally, a single slot is cut into the tire and the noise data are measured and studied. Air-borne noise is isolated by filling the slot with foam and comparing the resulting frequency spectra. Numerically, a previously developed computational fluid dynamics tire noise prediction model is employed to predict the air-borne noise for the same tire, under similar operating conditions. A direct comparison between the experimental and computational results is also presented in terms of pressure time traces and spectral characteristics. Comparisons indicate that the computational model is capable of predicting the noise generated by the air pockets in the tire. While providing a deeper understanding of the causes of air-borne noise, this paper also aims to demonstrate the use of a computational tool that can be used to obtain a reasonably accurate prediction of air-borne tire noise.

Direct computation of the sound generated by vortex pairing in an axisymmetric jet

1999 ◽  
Vol 383 ◽  
pp. 113-142 ◽  
Author(s):  
BRIAN E. MITCHELL ◽  
SANJIVA K. LELE ◽  
PARVIZ MOIN
Keyword(s):  
Mach Number ◽  
Stokes Equations ◽  
Near Field ◽  
Prediction Method ◽  
Axial Direction ◽  
Navier Stokes ◽  
Far Field ◽  
Source Terms ◽  
Vortex Pairing ◽  
Field Sound

The sound generated by vortex pairing in axisymmetric jets is determined by direct solution of the compressible Navier–Stokes equations on a computational grid that includes both the near field and a portion of the acoustic far field. At low Mach number, the far-field sound has distinct angles of extinction in the range of 60°–70° from the jet's downstream axis which can be understood by analogy to axisymmetric, compact quadrupoles. As the Mach number is increased, the far-field sound takes on a superdirective character with the dominant sound directed at shallow angles to the jet's downstream axis. The directly computed sound is compared to predictions obtained from Lighthill's equation and the Kirchhoff surface method. These predictions are in good agreement with the directly computed data. The Lighthill source terms have a large spatial distribution in the axial direction necessitating the introduction of a model to describe the source terms in the region downstream of the last vortex pairing. The axial non-compactness of the quadrupole sources must be adequately treated in the prediction method.

A Three-Dimensional Numerical Investigation of Air Pumping Noise Generation in Tires

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Prashanta Gautam ◽  
Abhilash J. Chandy
Keyword(s):  
Noise Reduction ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Near Field ◽  
Three Dimensional ◽  
Complex Nature ◽  
Noise Generation ◽  
Vehicle Noise ◽  
Tire Noise ◽  
Generation Mechanisms

Tire noise reduction is an important aspect of overall vehicle noise reduction. However, due to the complex nature of tire noise generation and correlation between various generation mechanisms, it is difficult to isolate, predict, and control tire noise. Air-related noise generation mechanisms in tires are tough to predict experimentally, resulting in the need for an accurate numerical model. Computational fluid dynamics (CFDs) is used here to propose a numerical tool capable of predicting air-pumping noise generation. Slot deformations are prescribed by custom functions instead of using structural solvers and the rotation of tire is represented by using mesh motion and deformation techniques. Near-field and far-field acoustic characteristics are predicted using fluid dynamic equations and acoustic models. The use of various spectral analysis tools show that the proposed model is capable of predicting the high frequency air-pumping noise while also predicting other air-related mechanisms such as pipe resonance, Helmholtz resonance, and rotational turbulence. This study is intended to provide an understanding of the various air-related noise generation mechanisms so that numerical models can be used in the future to predict tire acoustics economically and effectively.

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