Aero-acoustic investigation over a 3-dimensional open sunroof using CFD (original) (raw)
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When a commercial vehicle is driving with the sunroof open, it is easy for the problem of sunroof buffeting noise to occur. This paper establishes the basis for the design of a commercial vehicle model that solves the problem of sunroof buffeting noise, which is based on computational fluid dynamics (CFD) numerical simulation technology. The large eddy simulation (LES) method was used to analyze the characteristics of the buffeting noise with different speed conditions while the sunroof was open. The simulation results showed that the small vortex generated in the cab forehead merges into a large vortex during the backward movement, and the turbulent vortex causes a resonance response in the cab cavity as the turbulent vortex moves above the sunroof and falls into the cab. Improving the flow field characteristics above the cab can reduce the sunroof buffeting noise. Focusing on the buffeting noise of commercial vehicles, it is proposed that the existing accessories, including sun vi...
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.
Computational aero-acoustic analysis of a passenger car with a rear spoiler
Applied Mathematical Modelling, 2009
This study proposes an effective numerical model based on the Computational Fluid Dynamics (CFD) approach to obtain the flow structure around a passenger car with wing type rear spoiler. The topology of the test vehicle and grid system is constructed by a commercial package, ICEM/CFD. FLUENT is the CFD solver employed in this study. After numerical iterations are completed, the aerodynamic data and detailed complicated flow structure are visualized using commercial packages, Field View and Tecplot. The wind effect on the aerodynamic behavior of a passenger car with and without a rear spoiler and endplate is numerically investigated in the present study. It is found that the installation of a spoiler with an appropriate angle of attack can reduce the aerodynamic lift coefficient. Furthermore, the installation of an endplate can reduce the noise behind the car. It is clear that the vertical stability of a passenger car and its noise elimination can be improved. Finally, the aerodynamics and aero-acoustics of the most suitable design of spoiler is introduced and analyzed.
Simulation of the autobody aerodynamics for car interior noise control
2009 IEEE 10th International Conference on Computer-Aided Industrial Design & Conceptual Design, 2009
For the analysis of car interior noise at high speed, the influence of autobody aerodynamics should be taken into account, besides the vibration and acoustic radiation of powertrain, the random excitation from road and the vibration inputs of tires, and so on. A model of CFD was built. And the most turbulent area of autobody surfaces was located. The spectrum of average aerodynamic pressure of monitoring points on front door window was also obtained by unsteady calculation. So, the more accurate analysis of car interior noise can be processed due to loading the power inputs listed above to the simulation model, which is looked as the foundation of further optimization of car interior noise control.
Study and Design Frontal Area of a Car to Curtail Aerodynamic Noise
IJRASET, 2021
In this field of comparative research study, comparison of two car model, a standard car and an optimized car with respect to aerodynamic analysis/aeroacoustics analysis with the help of CFD software Ansys 2019 R2 version is taken in consideration to compare the results and get to know if the optimized car model has reduction in the generation of aerodynamic noise when it travels at four different speeds (30 m/s, 40 m/s, 50m/s and 60m/s). For carried out aeroacoustics/aerodynamic noise analysis two main model are used turbulence model and an acoustics model. For turbulence model and K-epsilon model is used as it is widely used for getting turbulence generation and for acoustics model a Broadband noise model is used to generate the results through numerical simulation and data sources. First a standard sedan car is modelled in Onshape CAD tool and aeroacoustics analysis is carried out on this standard sedan car to get to know the source of aerodynamic noise. From the standard car results made changes in the sedan car geometry like giving fillets to point/sharp edges of wheel arcs, front bumper, hood-line, fender and start of roofline from A-pillar, providing under-flush, optimizing A-pillar beam and optimizing outside rear view mirror and making them fully camera integrated mirror to reduce wake. After optimizing standard geometry carried out aerodynamic analysis with the same four different speed given for standard car (30 m/s, 40m/s, 50m/s and 60 m/s). Generated contour plots and isosurface from CFX for flow characteristics and acoustic sound source with various model like Proudman's acoustic power level in Db, Curle surface acoustic power level in decibels (dB) and also, Lilley S total noise source to show the sources of noise and how many decibels of noise is generated from those sources. Maximum of 100 decibels of noise is generated from the front bumper and a minimum of 80 decibels were monitored in the results process after comparing the results with standard car which has noise nearly 120 decibels with high fluctuations of turbulence kinetic energy and decrease in its pressure level.
Applied Mechanics and Materials, 2013
The wind tunnel measurement and numerical simulation of a 50% scaled sedan model surface pressure distribution were made in order to provide fundamental data for improving the Computational Fluid Dynamics (CFD) simulation accuracy of the aerodynamic noise related flow field around automobiles. The pressure measurement positions of the wind tunnel experiment were on the side window and the door. The wind tunnel test section speed was 30m/s at 0° yawing angle. As for the CFD simulation, the wind tunnel shape computational domain and four settings of the near wall computational mesh were made. Both the k-ω SST and the Realizable k-ε turbulence models were chosen. And three value ranges of the near wall computational mesh’s dimensionless wall distance (y+) were realized. Compared with the experimental data, the pressure coefficient (CP) simulation results showed good agreement with the measurement at the re-attaching region on the side window and the attaching region on the door. But th...
SAE Technical Paper Series, 2013
Nowadays, outer surface design of passenger cars is not just a matter of styling and safety but air flow around car body and exterior accessories has significant effect on fuel consumption, performance and dominantly on the wind noise. In recent years, passenger comfort is one of the most challenging and important automotive attributes for car makers. Controlling the turbulence eddies that causes aerodynamic noise can remarkably affect passenger's comfort quality. Identification of aerodynamic sources is considered as the first step in order to control the wind noise. In this research computational fluid dynamics method is applied to simulate the wind flow around the car and the investigation of aerodynamic noise pattern is performed by numerical method which is the most prevalent way that is used by auto industries. By the advent of virtual simulations and by implementing these methods for the purpose of predicting and modifying in the whole car design phase, a considerable reduction in the automotive design process time and cost has been achieved. This study includes two main sections: Firstly, identification of aerodynamic noise source around a coupe passenger car is investigated. For this purpose after CAD modeling, preparing model for simulation is performed in preprocessing CAE software and numerical calculations are done by using finite volume method. In fact, fluctuations of pressure on external surfaces of body are considered as the main cause for aerodynamic noise and in practice this phenomena is detected for the identification purpose. Hence, acoustic power level is the reference parameter for studying the wind acoustic quality. In order to investigate acoustic power, broad band noise model is applied for acoustics and realizable k-ε model is used for solving turbulence fluid. In the second section, rear spoiler is added to the vehicle and acoustic effects are studied. Results are compared with each other and the acoustic effects of the rear spoiler on the rear section of the car surface including the windshield, trunk lid and rear end parts are summarized using CAE tools.
Applied Acoustics, 2019
Vehicle interior noise level is the sum of the structure borne and air borne noises created on the road. Structure borne noises become less important at higher speeds and the airflow around the vehicle create the airborne wind noise. When the airflow comes across with the side mirrors, eddy currents create turbulent flow at the back of the mirror and near the A-pillar. Since the aerodynamic flow conditions frequently changes on the road (weather conditions, road obstacles, etc.), aerodynamic forces arise on the vehicle door. This aerodynamic door pressure distributions leads to complicated vibrations and increases interior noise level. The level of the wind noise conveyed from side door window sealing to the vehicle interior has a very significant effect on the customer's perception of vehicle overall quality. In the present study, aspiration noise induced by sealing gap between the door and the sealing was investigated. Aerodynamic forces were calculated by CFD simulations at different speeds of vehicle and then door deformations caused by these aerodynamic forces were calculated. On the other hand, physical door deformations were measured on the road to digitize the perceived interior noise. The correlation between the sealing gap and the perceived interior noise level was expressed by examining the door stiffness and sealing pressure on the door.
Wind noise from A-pillar and side view mirror of a realistic generic car model, DriAver
International Journal of Vehicle Noise and Vibration
Interior noise of a production car is a total contribution mainly from engine, tyres and aerodynamics. At high speed, wind noise can dominate the total interior noise. Wind noise is associated with the unsteadiness of the flow. For most production cars, A-pillar and side view mirror are the regions where the highly separated and turbulent flows are observed. This study quantifies the wind noise contribution from A-pillar and side view mirror with respect to the interior noise of a generic realistic model, DrivAer. The noise sources are obtained numerically from the flow-structure interactions based on the unsteady Reynolds averaged Navier stokes (URANS) while the noise propagation is estimated using Curle's equation of Lighthill acoustic analogy. The sound pressure frequency spectrum of the interior noise is obtained by considering the sound transmission loss from the side glass by using the mass law for transmission loss. The study found that the noise from the A-pillar is higher than the noise from the side view mirror in the whole frequency range. Near the end of the A-pillar component contributes the highest radiated noise level with up to 20 dB louder than that at the front part of the A-pillar.
Computational aero-acoustic modelling of external rear-view mirrors on a mid-sized Sedan
Noise & Vibration Worldwide, 2016
Ever-rising fuel costs necessitate design of fuel-efficient vehicles. Consequently, modern vehicle manufacturers are focused on designing low aerodynamic drag vehicles which would in-turn reduce the fuel consumption. This study analyses the contribution of external rear-view mirrors to the total drag force and the overall sound pressure level at the A, B and C pillars, while optimising the external rear-view mirror design accordingly. Solid Works renditions of external rear-view mirror models mounted on a reference luxury sedan were analysed using a commercially available computational fluid dynamic package ANSYS FLUENT. A different approach was followed to carry out the empirical flow visualisation and predict sound pressure levels. The aerodynamic characterisation of the vehicle was done utilising the widely used shear stress transport turbulence model, while the analysis of wind noise and the contributing vortices employed a large eddy simulation. This approach significantly redu...