Integrating CFD and Experiment: The Jaguar Land Rover Aeroacoustics Process (original) (raw)
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Vortex generation behind the A-pillar region due to airflow separation leads to aero-acoustics generation. The magnitude and intensity of the vortex and hence aero-acoustics activities are further enhanced when vehicle are exposed to crosswind especially when travelling on a highway. The objective of this project is to develop a computational fluid dynamic (CFD) and computational aeroacoustics (CAA) model to best simulate aerodynamic flow and aero-acoustics propagation behind the A-pillar region of simplified vehicle with varying windshield radii under various yaw conditions. The CFD model will then be used to investigate and better understand the aerodynamic and aero-acoustics distribution behaviour surrounding area of the vehicle A-pillar region. The simplified vehicle model used was of 40% scale. Models investigated consist of three models of different circular windshield/A-pillar radii and two models of with sharp A-pillar edges with different windshield slant angle. Models used in this project were subjected to 0°, 5°, 10° and 15° yaw angles. The models were modelled under laboratory conditions, exposed to boundary inlet velocities of 60, 100 and 140 km/h. The development of the CFD model consists of first investigating and selecting the best grids configurations for both the circular and sharp edge A-pillar models at various respective yaw angles. The process was then to select the best turbulence and near wall model for the CFD model. The grids, turbulence and near wall models selected for comparison were investigated from commercial CFD software's FLUENT and SWIFT AVL. The final stage in the development of the numerical model was to develop a CAA model for the aero-acoustics modelling. The final grid configuration selected for the CFD models in this project was the polyhedral grids from SWIFT. The final selection of turbulence and near wall model selected was the standard k-ε turbulence model and the near wall model of Chieng and Launder (1980) for the circular models at 0° yaw. For all the other models at various yaw angles, the turbulence and near wall model of choice was the RSM with the WEB near wall model. Validation of the final CFD model against the experimental data of Alam (2000) resulted in good correlations. DECLARATION OF ORIGINALITY I, Nurul Muiz Murad, hereby declare that this thesis contains no material, which has been accepted for the award of any other degree or diploma in any university or institute of education. To the best of my knowledge and belief, no material in this thesis has been previously published or written by another person except where due references is made in the body of the thesis.
The Update of an Aerodynamic Wind-Tunnel for Aeroacoustics Testing
Journal of Aerospace Technology and Management, 2014
This paper describes the update and characterization of a previously pure aerodynamics wind-tunnel into a facility able to simultaneously execute aerodynamics and aeroacoustics testing. It is demonstrated that the application of high-performance acoustic materials on strategic positions of the wind-tunnel circuit and punctual actions can substantially reduce the background-noise level. This paper shows efficient measures which resulted to broadband-noise reduction of up to 5 dB and practically complete removal of spectral tones. In addition, it is demonstrated that the applied acoustic treatment reduced the turbulence level, measured at the test-section at maximum operational velocity, from the previous 0.25% level to 0.21%. As a minor penalty, the acoustic treatment reduced the flow velocity in 2% for the same electric-power input. Finally, the work described in this paper resulted on a wind-tunnel with good flow quality and capacity for aeroacoustics testing.
27TH INTERNATIONAL CONGRESS OF THE AERONAUTICAL SCIENCES
The present paper shows the results of the update of a previous aerodynamics wind-tunnel into a wind-tunnel with capacity to execute aeroacoustics tests, while keeping its good aerodynamic qualities. In order to reduce the wind tunnel background noise level, melamine foam was applied on wind-tunnel walls, and an acoustic baffle was installed between corner vane sections. Also a treatment was applied to the tip fan to the tip fan blades and the noise generated by the electric motor was insulated. Results showed a reduction of up to 5 dB and a noticeable removal of spectral tones after the wind-tunnel treatment. Another positive effect of the noise reduction was the decrease of test section turbulence, from its previous level of 0.25% to 0.21%. As a minor penalty, the insertion of noise treatment caused a maximum flow velocity maximum reduction of 2% for the same electric power input. All this process, described by the present paper, resulted on a wind-tunnel with good flow quality and capacity for aeroacoustics measurements.
Aeroacoustic Facade Noise Validation: A Comparison of CFD and Wind Tunnel Tests
Building Simulation Conference proceedings
Computational fluid dynamics (CFD) analysis is a valuable alternative to wind tunnel testing for analysing and predicting aeroacoustic noise. However, transient simulations require a very fine grid and short time step to resolve acoustic pressure fluctuations, resulting in a computationally intensive process. This paper investigates the possibility of using steady state CFD simulations as a fast alternative to transient simulations for characterizing the noise production of perforated façade panels. It compares both transient and steady-state Reynolds-averaged Navier-Stokes (RANS) simulations of aeroacoustically active perforated panels to measurements of specimens in a reverberation chamber. Accurate sound power predictions can be achieved for broadband noise from normally incident wind on perforated panels, but sound power and frequency remain difficult to predict for oblique wind directions.
Aero-acoustic investigation over a 3-dimensional open sunroof using CFD
IRJET, 2022
Buffeting noise, a common phenomenon observed in moving vehicles, is an acoustic response due to the difference in aerodynamics around openings like sunroofs and side windows. The reduction of the resultant acoustic noise has been the area of interest of aerodynamicists. The research work of this project aims to establish the basis for the design of a deflector that solves the problem of sunroof buffeting noise in a three-dimensional simplified car model. This will be executed through Computational Fluid Dynamics (CFD) numerical simulation technology. The pressure characteristics of buffeting noise at different speed conditions are to be analyzed. The pressure distribution around the sunroof will help establish an efficient design for a deflector. The Detached Eddy Simulation (DES) method is chosen for this analysis because it is conventionally used for acoustic-based studies. Additionally, since the conditions at maximum noise are intended to be modelled, compressibility is incorporated in the fluid model. The domain around the car model will be constructed to replicate a three-dimensional wind tunnel, and the boundary conditions will be assigned accordingly. The observations obtained about buffeting will be used to brainstorm the design, sizing and positioning of the deflector.
2019
The main reason why wind farms cannot be installed close to people's habitats is the noise pollution they generate while working. This paper studies a flow area, which is analyzed on the 3D S809 blade profile using the SST k-ω turbulence model to calculate the near-field flow of wind turbines. The attached a time-dependent flow field factors in Ffowcs-Williams and Hawkings (FW-H) equating Sound Pressure Level (SPL) was calculated for different velocities as 5.4 m/s and 7 m/s from the microphone placed in the computational domain to be analyzed. In this study, the NREL phase VI small scale (12%) baseline airfoil type was used. The acoustic results and torque values obtained from the analyzes were compared both with the data in the literature and among themselves. As a result; one of the calculated torque values was under the literature amount. This differentiation maybe since the analysis given in the literature contains a higher number of mesh cells. SolidWorks software was used...
Automotive aeroacoustics: An overview
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2017
Vehicle aeroacoustic performance has a major influence on customer perception and also has importance for safety and comfort. Wind noise performance was once differentiated by the quality of sealing. Today, achieving competitive wind noise performance also depends on minimising aeroacoustic noise sources generated by the vehicle form, and on attenuation in the noise pathway from sources on the exterior to the vehicle interior. The reduction in noise transmission, especially through glazed surfaces, will continue to play an important role in controlling cabin noise, with a particular emphasis on achieving attenuation efficiently in terms of component mass. The human brain is not only sensitive towards the level of steady broadband noise, but distinctive features such as tonality or modulation draw the attention of the vehicle occupant and impact negatively on perception. Complex indices are often required to define good wind noise performance. This includes the consideration of multi...
Assessment of Aeroacoustic Simulations of the High-Lift Common Research Model
25th AIAA/CEAS Aeroacoustics Conference, 2019
This paper presents further validation of PowerFLOW R aeroacoustic simulations of the High-Lift Common Research Model through comparisons with experimental data from a recently completed wind tunnel test. Preliminary timeaveraged surface pressure and microphone array data from the experiment are in reasonably good agreement with the simulations, and the slat is shown to be a dominant noise source on this model. The simulations did not predict slat tones that were very prominent in the experiment, but they did capture the broadband component of slat noise in the low-frequency range up to 1 kHz at full scale. Future tests are planned to demonstrate slat noise reduction technology, and simulations are being used to guide this development. Nomenclature a speed of sound f frequency C p coefficient of pressure FSS full-span slat M Mach number = |V|/a PSD power spectral density (dB/Hz) PSS part-span slat |V| magnitude of velocity vector rms root mean square VR variable resolution x, y, z Cartesian coordinates Greek: η normalized spanwise distance
Lecture 1: Introduction to experimental aeroacoustics
hal-04437042v1, 2017
This introductory lecture gives an overview of the challenges and pitfalls of wind tunnel experiments in aeroacoustics. Most concepts introduced here will be developed in following lectures. 1.0 EXPERIMENTAL AEROACOUSTICS: WHAT FOR? 1.1 The Origin of Experimental Aeroacoustics Strouhal [1] was probably the first to relate sound generation to fluid motion in 1878 in his experimental investigation of Aeolian tones generated by a stretched wire, but he incriminated fluid friction as the origin of the radiated sound. It was only in 1915 that Lord Rayleigh [2] related the sound radiation to the periodic vortex shedding after discovering that even rigid cylinders produce Aeolian tones when placed in a flow, which really was the beginning of aeroacoustics as a branch of flow physics. The next jump of aeroacoustics also came along with experimental evidence of the extreme acoustic nuisance caused by the first jet engines that led to the pioneering work of Sir J. Lighthill [4], [5] about the physics of jet noise, followed by many others who investigated the role of solid surfaces in turbulent flows. This advance also revealed a need for aeroacoustic investigations in wind-tunnel experiments, which provided information that could not be measured on real flying aircrafts. The latest step of aeroacoustics came along with the progress of unsteady high-order Computational Fluid Dynamics (CFD) and CFD in general, that became applicable to aeroacoustic problems [6], [7], [8], [9] giving birth to a new branch of aeroacoustics, Computational AeroAcoustics (CAA). This progress also fostered a new type of aeroacoustic experiments, so-called benchmark experiments, whose role it is to provide verification, validation and calibration data for CFD codes. Today a new age is dawning with the upcoming of highly efficient and versatile CFD methods (such as LBM) on one hand and the rise of high-resolution experimental tools on the other hand. These tools (such as time resolved PIV or multi-sensor pressure arrays based on MEMS technologies) become increasingly accurate, reliable and applicable to aeroacoustic investigations. These developments will certainly deeply modify our approach to aeroacoustics in the next decade: the process has already begun. 1.2 Motivation for Experimental Aeroacoustics This brief introductory history of aeroacoustics highlights the three types of experimental approaches that are still encountered in our community's wind tunnels as well as the purposes they are designed for. 1.2.1 Fundamental Aeroacoustics Experiments for fundamental studies in aeroacoustics are meant to characterise basic mechanisms of sound