Fred Mendonça’s research while affiliated with CD-adapco and other places

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Publications (11)


Turbulent Surface Pressure Field in Low Speed Flow
  • Chapter

November 2015

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54 Reads

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4 Citations

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Vincent Cotoni

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Phil Shorter

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Fred Mendonça

The external air low speed flow over a flat plate passed a half cylinder shape is computed using an unsteady CFD technique; the turbulent surface pressure field is analyzed in details; a frequency-wavenumber decomposition is used to identify the convective and acoustic energy concentration. A comparison is then made with results obtained using several standard semi-analytical models of turbulent surface pressure. Finally the wall pressure fluctuations are used as a load on an elastic plate in a vibroacoustic analysis and the transmitted noise inside a trimmed acoustic cavity is computed. Some conclusions are drawn on the pertinence of using a semi-analytical model or unsteady LES-type CFD computations to describe the wall pressure loading for a vibroacoustic analysis.


Predicting the Noise Transmission through a Structure Loaded with a Low Mach Number Turbulent Flow

June 2014

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46 Reads

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4 Citations

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Fred G. Mendonca

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Vincent Cotoni

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[...]

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Terence Connelly

This paper presents two concurrent simulation strategies suited to compute the noise induced by external aerodynamic flows inside of vehicles. A typical applied problem would be the noise in a car induced by the flow around a side mirror. The traditional approach relies on a compressible, transient CFD computation. The result of such a computation contains both the vortical and acoustic pressure contributions: it can immediately be used in a standard vibroacoustic strategy to compute the noise inside of a vehicle. The second approach relies on an incompressible CFD strategy, complemented by an acoustic solver. The paper discusses some advantages of this second strategy and gives illustrations on an SAE body (simplified car concept).


Fig.1: Geometry and Grid system.
Transitional Flow and Aeroacoustic Prediction of NACA0018 at Re=1.6x10^5
  • Conference Paper
  • Full-text available

June 2014

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304 Reads

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3 Citations

Laminar to turbulent transition flow over NACA0018 airfoil at Re=1.6×105 via the growth of Tollmein-Schlichting (TS) instability waves and its associated aeroacoustical noise is studied numerically, and compared with measurements and a previous computational study. The present computations were carried out using STAR-CCM+, a commercial unstructured CFD code which is capable of direct simulation of noise. Fully wall-resolved Large Eddy Simulation with WALE (Wall Adapting Local Eddy viscosity) as the subgrid-scale model is employed for better transitional prediction of flow field around the airfoil. For this configuration at an angle of attack 6°, the model predicts the growth of TS-waves, transition on the suction surfaces and turbulent interaction with the trailing edge, resulting in an acoustic tonality between 2.2-2.3kHz. The computed FW-H impermeable (dipolar) propagation demonstrates good accuracy compared with experiment in terms of SPL and frequency of fundamental tone, predicted at 2.36 kHz and its first harmonic at 4.7 kHz. The Reynolds stresses also compare well with experiment, and demonstrate a significant improvement to previous published computational results.

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Figure 1. CAD with mesh on the symmetry-plane
Figure 2. HSM Simplified vehicle structure [6]
Figure 3. STL comparison 4-mm side glass vs. 12-mm wall structure + NCT
Figure 4. Statistical estimate of modes-in-band: 4-mm glass vs. interior cavity
CAE-Based Prediction of Aero-Vibro-Acoustic Interior Noise Transmission for a Simple Test Vehicle

April 2014

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513 Reads

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7 Citations

SAE Technical Papers

The interior noise in a vehicle that is due to flow over the exterior of the vehicle is often referred to as 'windnoise'. In order to predict interior windnoise it is necessary to characterize the fluctuating surface pressures on the exterior of the vehicle along with vibro-acoustic transmission to the vehicle interior. For example, for greenhouse sources, flow over the A-pillar and side-view mirror typically induces both turbulence and local aeroacoustic sources which then excite the glass, and window seals. These components then transmit noise and vibration to the vehicle interior. Previous studies by the authors have demonstrated validated CFD (Computational Fluid Dynamics) techniques which give insight into the flow-noise source mechanisms. The studies also made use of post-processing based on temporal and spatial Fourier analysis in order to quantify the amount of energy in the flow at convective and acoustic wavenumbers. In the present study, the previously validated transient CFD techniques are used to describe sources that are input to frequency-based vibro-acoustic methods in order to predict interior noise. This combined aero-vibro-acoustic simulation approach is supported by an experimental programme initiated by Hyundai Motor Company (HMC) in which measurements of the internal noise were made on a simplified test structure at two speeds (110kph and 130kph), and two yaw conditions (0° and 10°), against which the predicted interior noise levels are compared.


Fig. 1 Hyundai simple model
Fig. 2 Mesh distribution in the aperture region
Fig. 3 Modeling process hierarchy 
Fig. 5 FRET pressure-time signal at driver’s ear lo- cation(left), SPL(dB) (right) 
Fig. 6 Curve fit approximation to the decaying pressure signal from FRET 
Numerical Analysis of Sunroof Buffeting using STAR-CCM+

March 2014

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1,161 Reads

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1 Citation

Transactions of the Korean Society for Noise and Vibration Engineering

CFD flow simulation of vehicles with open sunroof and passenger window help the automotive OEM(original equipment manufacturer) to identify the low frequency noise levels in the cabin. The lock-in and lock-off phenomena observed in the experimental studies of sunroof buffeting is well predicted by CFD speed sweep calculations over the operating speed range of the vehicle. The trend of the shear layer oscillation frequency with vehicle speed is also well predicted. The peak SPL from the CFD calculation has a good compromise with the experimental value after incorporating the real world effects into the CFD model by means of artificial compressibility and damping correction. The entire process right from modeling to flow analysis as well as acoustic analysis has been performed within the single environment i.e., STAR-CCM+.


Validation of a New Hybrid CAA Strategy and Application to the Noise Generated by a Flap in a Simplified HVAC Duct

May 2009

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439 Reads

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39 Citations

This paper is the continuation of the work started last year by the consortium of the German car manufacturers Audi, BMW, Daimler, Porsche and Volkswagen that has presented the paper titled Numerical and Experimental Investigations of the Noise Generated by a Flap in a Simplified HVAC Duct. 1 In this paper, the first steps of an investigation carried out by the consortium is described. The feasibility of correctly predicting the aero-dynamically generated noise within an HVAC system by means of CFD (Computational Fluid Dynamics) and CAA (Computational Aeroacoustics) is assessed. In the previous paper the experimental setup and the CFD efforts have been described and compared, but no acoustic post-processing had been presented. This paper is thus the natural continuation, with utilization of the CFD results obtained in.1 Some improvements of the Actran software have been made thanks to the cooperation with both the industrials of the working group and the CFD vendor CD-adapco. A short introduction explains the objectives of the study. The advantages of the new mapping technique are explained, as well as the need to damp out progressively the sources produced by the CFD code. The experimental setup and CFD are then shortly reminded, with some focus on the acoustic specificities. Finally, the CFD results are exploited in the commercial acoustic simulation software Actran. Acoustic results are compared with experimental ones, showing a fair agreement.


Optimal Sunroof Buffeting Predictions with Compressibility and Surface Impedance Effects

May 2005

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51 Reads

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4 Citations

Computational Fluid Dynamic (CFD) studies of sunroof buffeting on production vehicles demonstrate accurate prediction of the main buffeting frequency and its harmonics. For production vehicles, none to date has illustrated the phenomenon of buffeting intensity maximization over a vehicle speed range, at a frequency related to the volume of the passenger compartment. All assume that the interior surfaces of the vehicle are rigid, potentially overestimating in-cabin noise intensities by failing to account for surface impedance from non-acoustically rigid trims and linings. In this paper, a modelling study of both effects is presented. Advanced LES-type turbulence modelling, in the form of Detached Eddy Simulation (DES), is used. The hybrid approach, linking acoustic source generation in CFD to acoustic pressure wave propagation with Boundary Element Methods (BEM), is adopted. The former is used to predict the surface pressure excitations induced by the flow, the latter to interpret these as equivalent dipoles to be propagated. The results confirm both the necessity of accounting for compressibility effects in the CFD solver when predicting the buffeting intensity maximization, and surface impedance affects on noise levels perceived by the driver and passengers at higher frequencies closer to the peak audibility range.




Comparison Between Measured and Predicted Tonal Noise from a Subsonic Fan Using a Coupled Computational Fluid Dynamics (CFD) and Computational Acoustics (CA) Approach

May 2004

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453 Reads

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5 Citations

The flow through an HVAC blower fan, typical to the automotive industry, was solved using STAR-CD. Time varying pressure data was then exported to ACTRAN/TM where the CFD results were decomposed into acoustic duct modes, using a multiple plane matching method. These duct modes were then propagated to far field locations and compared with experimental data at the blade passing frequency, obtained in the semi-anechoic chamber at Denso Thermal Systems. Good agreement was attained for microphones located downstream of the inlet and outlet ducts. At the other microphone locations there is doubt that the dominant noise generation mechanism is purely aeroacoustic: vibroacoustic noise sources are present. Since aeroacoustic noise sources alone were modeled, there was a deterioration in the simulation/experimental comparison.


Citations (9)


... Okutsu et al. [6] investigated the mechanism of automobile aerodynamic noise which transmits to the inside of a cabin with both experimental measurements and numerical simulations for a full scale automobile model. Caro et al. [7] analyzed the turbulent surface pressure field using detached-eddy simulation (DES), and conducted frequency-wavenumber decomposition to identify the convective and acoustic energy concentration. Yao and Davidson [8,9] carried out vibro-acoustic simulations to investigate the hydrodynamic and acoustic contributions to the interior noise of a cabin with a wavenumber-frequency decomposition method. ...

Reference:

On turbulent flow and aerodynamic noise of generic side-view mirror with cell-centred finite difference method
Turbulent Surface Pressure Field in Low Speed Flow
  • Citing Chapter
  • November 2015

... In recent years, many numerical investigations of the problem were conducted, using different methods for sound calculation. Mendonca et al. [10] simulated the fully compressible flow around a simplified car model and used vibroacoustic and aeroacoustic methods to compute the sound pressure level in the interior. Similar investigations were also done on real car models, for example by Schell and Cotoni [11,12], who used a hybrid approach consisting of an incompressible Computational Fluid Dynamics (CFD) simulation, frequency domain finite element computations and a statistical energy analysis (SEA) model for the interior cabin. ...

CAE-Based Prediction of Aero-Vibro-Acoustic Interior Noise Transmission for a Simple Test Vehicle

SAE Technical Papers

... According to the experimental condition [19], the OASPL and the SPL are calculated by the simulation method of Section 2.2. As shown in Figure 6b, it can meet the accuracy standard [26] that the errors of the upper point and lower point were both controlled to be less than 1.5%. For the spectrum in Figure 6c, the gross trend of the SPL is the same, and the frequency location of the peak is the same as that of the experimental results. ...

Transitional Flow and Aeroacoustic Prediction of NACA0018 at Re=1.6x10^5

... The wall pressure fluctuations measured in the experiments contain both the convective and acoustic parts. The latter is much smaller than the former (Caro et al. 2014;Dawi and Akkermans 2019), so the wall pressure fluctuations are approximately regarded as composing only the convective part. By checking all the 21 measuring points on the flat plate, we observe that the wall pressure fluctuations in the middle region of the side-view mirror wake (i.e. the area between -10° and +10°) are much greater than those of the monitoring points in other areas, which is in agreement with the statement by Chen et al. 2009. ...

Predicting the Noise Transmission through a Structure Loaded with a Low Mach Number Turbulent Flow
  • Citing Conference Paper
  • June 2014

... It is interesting to note that similar configurations, mainly conducted with circular geometries both for the duct and the orifice, have been the subject of many papers in the recent years and we can cite the work of Sovardi et al. [12], Karban and Schram [13,14], Sack et al. [15,16], and also [17]. In a somewhat more industrial context, other research work investigated the ability of different CFD software to predict broadband noise and the presence of tonal noise, see [18][19][20] for instance. Both experimental and numerical aspects are presented here in a rectangular duct. ...

Aeroacoustic Simulation of Double Diaphragm Orifices in an Aircraft Climate Control System
  • Citing Conference Paper
  • May 2005

... The phenomenon of the flow-related acoustic wave generation is the subject of many works focused on the identification of basic mechanisms of sound generation. In Ref. [6], a numerical analysis is presented of the operation of a typical-geometry Helmholtz resonator placed in a fluid flow. In Ref. [7], an analysis is conducted of the flow along a cavity with a lid, characterized by a geometry similar to the one analysed herein and operating in conditions corresponding to the Helmholtz resonator. ...

Aeroacoustic Simulation of the Noise Radiated by an Helmholtz Resonator Placed in a Duct

... We remark that the fluid and acoustic grids might have very different granularities in order to capture the underlying (different) physics. While simple nearest neighbour interpolation fails to compute the acoustic sources accurately [7], conservative interpolation schemes lack of important analytical framework, although have been successfully employed, see for instance [29]. The L 2 -projection method has been employed in [41] limited to nested Cartesian. ...

Validation of a New Hybrid CAA Strategy and Application to the Noise Generated by a Flap in a Simplified HVAC Duct

... For low-Mach number turbomachines as the present centrifugal fan, the primary noise sources are of dipole kind, e.g. see [23,24], and are due to a pulsating force due to the aerodynamic interaction between impeller and volute tongue. Therefore, the dipole source originating from the unsteady forces was considered as the dominant noise source of the fan in this study. ...

Investigation of the Tonal Noise Radiated by Subsonic Fans Using the Aero-Acoustic Analogy
  • Citing Article
  • January 2003

... Since the aeroacoustic noise is the consequence of turbulent flow, it is important to consider a proper model accordingly. Various models have considered this issue [77][78][79], and in almost all of them, the distribution along with the grid density has been taken into account. The fact is that the calculation time and cost should be evaluated to reduce the time and cost for calculations. ...

Comparison Between Measured and Predicted Tonal Noise from a Subsonic Fan Using a Coupled Computational Fluid Dynamics (CFD) and Computational Acoustics (CA) Approach