Numerical and experimental research on flow and aerodynamic noise characteristics of coach

2020 ◽  
pp. 095440702097381
Author(s):  
Yifei Chang ◽  
Zhigang Yang ◽  
Qiliang Li
Keyword(s):  
Flow Field ◽  
Acoustic Pressure ◽  
Low Frequency ◽  
The Body ◽  
Scale Model ◽  
Aerodynamic Noise ◽  
Band Pass Filter ◽  
Eddy Simulation ◽  
Noise Characteristics ◽  
Turbulent Pressure

The researches on flow and aerodynamic noise characteristics of coaches are urgently needed to improve with the rapid development of new energy coaches. In this paper, tests in model wind tunnel and numerical calculations were carried out to study the phenomenon of flow and aero-noise on 1:25 scale model coach. Based on large eddy simulation (LES) and detached eddy simulation (DES), reliable numerical calculation method of flow and aero-noise on coach was established and verified. It is found that the maximum difference on turbulent pressure between test and LES is less than 10 dB(A) while that of DES is about 20 dB(A). Due to the results got from 1:25 scale model, the W_LES_HOA model is used to obtain the flow field and sound field information outside the coach. To find out the different propagation characteristics of turbulent pressure pulsation and acoustic pressure, proper orthogonal decomposition (POD) and band-pass filter analysis are used for further analysis. For rearview mirror, the energy of first mode is 6.1%, and only the first nine modes have an energy for more than 3.0%. By the reconstruction of first four modes, it can be seen that the complicated transverse vortex shedding couples with A pillar vortex and reaches the body surface. However, the coupling of turbulent pressure can only be seen clearly under low frequency around 250 Hz while the coupling of acoustic pressure can be seen under 750 Hz. Meanwhile, with the analysis of low frequency round 250 Hz and 500 Hz, the change of flow field generated by airflow impingement on the windward surface and A pillar makes the front of the coach becomes the main sources of aerodynamic sound sources.

Study on flow field and aerodynamic noise of electric vehicle rearview mirror

2021 ◽  
pp. 095440702110228
Author(s):  
Xiaowei Hao ◽  
Zhigang Yang ◽  
Qiliang Li
Keyword(s):  
Flow Field ◽  
Proper Orthogonal Decomposition ◽  
Electric Vehicle ◽  
Sound Pressure ◽  
Pressure Level ◽  
Orthogonal Decomposition ◽  
Aerodynamic Noise ◽  
Turbulent Pressure ◽  
Rearview Mirror ◽  
Proper Orthogonal

With the development of new energy and intelligent vehicles, aerodynamic noise problem of pure electric vehicles at high speed has become increasingly prominent. The characteristics of the flow field and aerodynamic noise of the rearview mirror region were investigated by large eddy simulation, acoustic perturbation equations and reduction order analysis. By comparing the pressure coefficients of the coarse, medium and dense grids with wind tunnel test results, the pressure distribution, and numerical accuracy of the medium grid on the body are clarified. It is shown from the flow field proper orthogonal decomposition of the mid-section that the sum of the energy of the first three modes accounts for more than 16%. Based on spectral proper orthogonal decomposition, the peak frequencies of the first-order mode are 19 and 97 Hz. As for the turbulent pressure of side window, the first mode accounts for approximately 11.3% of the total energy, and its peak appears at 39 and 117 Hz. While the first mode of sound pressure accounts for about 41.7%, and the energy peaks occur at 410 and 546 Hz. Compared with traditional vehicle, less total turbulent pressure level and total sound pressure level are found at current electric vehicle because of the limited interaction between the rearview mirror and A-pillar.

scholarly journals EFFECT OF THE SPANWISE DISCRETISATION ON TURBULENT FLOW PAST A CIRCULAR CYLINDER

2021 ◽  
Vol 158 (A1) ◽  
Author(s):  
S Kim ◽  
P A Wilson ◽  
Z Chen
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Turbulent Flow ◽  
Three Dimensional ◽  
Scale Model ◽  
Spatial Density ◽  
Eddy Simulation ◽  
Large Eddy

The effect of the spanwise discretisation on numerical calculations of the turbulent flow around a circular cylinder is systematically assessed at a subcritical Reynolds number of 10000 in the frame of three-dimensional large-eddy simulation. The eddy-viscosity k-equation subgrid scale model is implemented to evaluate unsteady turbulent flow field. Large-eddy simulation is known to be a reliable method to resolve such a challenging flow field, however, the high computational efforts restrict to low Reynolds number flow or two-dimensional calculations. Therefore, minimum spatial density in the spanwise direction or cylinder axis direction needs to be carefully evaluated in order to reduce high computational resources. In the present study, the influence of the spanwise resolutions to satisfactorily represent three- dimensional complex flow features is discussed in detail and minimum spatial density for high Reynolds flow is suggested.

Computation of aerodynamic noise of centrifugal fan using large eddy simulation approach, acoustic analogy, and vortex sound theory

2007 ◽  
Vol 221 (11) ◽  
pp. 1321-1332 ◽  
Author(s):  
Q Liu ◽  
D Qi ◽  
H Tang
Keyword(s):  
Large Eddy Simulation ◽  
Broadband Noise ◽  
Scale Model ◽  
Aerodynamic Noise ◽  
Centrifugal Fan ◽  
Acoustic Analogy ◽  
Vortex Sound ◽  
Eddy Simulation ◽  
Sound Theory ◽  
Large Eddy

Large eddy simulation is applied to solve the unsteady three-dimensional viscous flow in the whole impeller-volute configuration of a centrifugal fan. The results of the simulation are used to predict the impeller-volute interaction and to obtain the unsteady pressure, velocity, and vorticity fluctuations in the impeller and volute casing. The simulation at the design point is carried out with the wall-adapting local eddy-viscosity subgrid-scale model and a sliding mesh technique is applied to consider the impeller-volute interaction. The results show that a strongly unsteady flow field occurs in the impeller and volute casing of the fan, and the flow is characterized with obvious pressure and vorticity fluctuations, especially at the tongue and at the blade wake region. The large pressure fluctuation at the tongue and the large fluctuation of the blade wake vorticity appear as the blade wake is passing the tongue. Acoustic analogy and vortex sound theory are used to compute the radiated dipole and quadrupole sound fields, which are in good agreement with the experiment. The sound results show that the vortex sound theory is convenient for the broadband noise computation, and the dipole sound is much higher than the quadrupole sound. The dipoles, distributed over the volute tongue surface, are the dominant sound source of the fan.

Analysis of Vehicle Interior Low-Frequency Noise Based on ATV

2014 ◽  
Vol 494-495 ◽  
pp. 78-81
Author(s):  
Long Ma ◽  
Wen Feng Xia
Keyword(s):  
Acoustic Pressure ◽  
Ride Comfort ◽  
Low Frequency ◽  
Coupled System ◽  
The Body ◽  
Frequency Noise ◽  
Vehicle Interior ◽  
Fem Model ◽  
Acoustic Structure ◽  
Acoustic Cavity

The FEM model of the body and acoustic cavity are created, and the acoustic-structure coupled system is built up,and the SPL(sound press level) of points corresponding to the drivers ear and passengers ears were calculated using software LMS.virtual.lab. And there are several relatively noticeable acoustic pressure peaks around 60Hz, 102Hz, 120Hz and 168Hz. The maximum noise value was calculated by using the method of ATV method, several suggestions are advised to decrease the vehicle interior noise so that the vehicle ride comfort could be improved.

scholarly journals Flow and Noise Characteristics of Centrifugal Fan under Different Stall Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Lei Zhang ◽  
Shoufang Liang ◽  
Chenxing Hu
Keyword(s):  
Flow Field ◽  
Power Level ◽  
Aerodynamic Characteristics ◽  
Rotating Stall ◽  
Field Analysis ◽  
Aerodynamic Noise ◽  
Navier Stokes ◽  
Implicit Time ◽  
Centrifugal Fan ◽  
Noise Characteristics

An implicit, time-accurate 3D Reynolds-averaged Navier-Stokes (RANS) solver is used to simulate the rotating stall phenomenon in a centrifugal fan. The goal of the present work is to shed light on the flow field and particularly the aerodynamic noise at different stall conditions. Aerodynamic characteristics, frequency domain characteristics, and the contours of sound power level under two different stall conditions are discussed in this paper. The results show that, with the decrease of valve opening, the amplitude of full pressure and flow fluctuations tends to be larger and the stall frequency remains the same. The flow field analysis indicates that the area occupied by stall cells expands with the decrease of flow rate. The noise calculation based on the simulation underlines the role of vortex noise after the occurrence of rotating stall, showing that the high noise area rotates along with the stall cell in the circumferential direction.

Flow and Noise Characteristics of Airfoils With Application to Turbomachinery

Volume 3 ◽  
2004 ◽  
Author(s):  
S. Lee ◽  
H.-J. Kim ◽  
W.-S. Song ◽  
F. E. C. Culick ◽  
N. Fujisawa
Keyword(s):  
Finite Thickness ◽  
Suction Side ◽  
Scale Model ◽  
Frequency Noise ◽  
Pressure Side ◽  
Trailing Edge ◽  
Eddy Simulation ◽  
Noise Characteristics ◽  
Turbulent Vortex Shedding ◽  
Late Transition

The flow-fields around airfoils in a uniform flow under the generation of noise were numerically studied and compared with experimental data. The numerical simulation was carried out by a large-eddy simulation that employs a deductive dynamic model as a subgrid-scale model. The result for a symmetrical airfoil at small angle of attack α = 3°–6° indicates that the discrete or narrow-banded frequency noise is generated when the separated laminar flow reattaches near the trailing edge of the pressure side and a strong instability thereafter affects positive vortices shed near the trailing edge. This type of forced transition or late transition instabilities near the trailing edge of the pressure side, interacting with convected vortices in an attached T.B.L. on the suction side, can be found in many practical airfoils of impellers rotating at moderate speeds under design conditions. The sound spectra derived from the aero-acoustic computations of airfoils indicate a dipole nature of sound having a narrow-banded or discrete peak by laminar instability and turbulent vortex shedding from their trailing edges of finite thickness at a Strouhal frequency, a quadrupole sound by turbulent broadband boundary-layer noise, or a mixed mode depending on flow conditions near the T.E.

Aerodynamic noise prediction of passenger vehicle with hybrid detached eddy simulation/acoustic perturbation equation method

2018 ◽  
Vol 233 (10) ◽  
pp. 2390-2404 ◽  
Author(s):  
Liyuan Zhong ◽  
Qiliang Li ◽  
Yigang Wang ◽  
Zhigang Yang
Keyword(s):  
Energy Analysis ◽  
Ride Comfort ◽  
Aerodynamic Noise ◽  
Perturbation Equation ◽  
Statistical Energy Analysis ◽  
Detached Eddy Simulation ◽  
Passenger Vehicle ◽  
Acoustic Perturbation ◽  
Eddy Simulation ◽  
Turbulent Pressure

Aerodynamic noise significantly affects the ride comfort of vehicle. A hybrid method combining detached eddy simulation and acoustic perturbation equations was used together with wind tunnel experiment to perform the aerodynamic noise investigation of a passenger vehicle. A good agreement of exterior overall sound pressure level and turbulent pressure spectra was found between the experiment and simulation with 260 million cells. Both turbulent and acoustic pressures were used as power input in statistical energy analysis, and the predicted interior noise is consistent with the experiment. The turbulent and acoustic pressures show a closely related spatial distribution, while the distribution patterns are different due to the distinction in their ways of propagation. The turbulent pressure travels downstream together with flow, while the acoustic pressure radiates homogeneously. Through statistical energy analysis, the major aerodynamic noise sources are identified as underbody for frequencies under 200 Hz and windows above 200 Hz, respectively. Finally, the studies of mesh resolution show that the finer mesh with 260 million cells can provide better results, while the coarser mesh with 90 million cells performs relatively poorly.

scholarly journals Interaction of turbulence with the leading-edge stagnation point of a thin aerofoil

2016 ◽  
Vol 798 ◽  
pp. 436-456 ◽  
Author(s):  
Lorna J. Ayton ◽  
N. Peake
Keyword(s):  
Stagnation Point ◽  
Isotropic Turbulence ◽  
Low Frequency ◽  
Leading Edge ◽  
The Body ◽  
Single Frequency ◽  
Asymptotic Model ◽  
Nose Radius ◽  
Asymptotic Results ◽  
Turbulent Pressure

An asymptotic model is constructed to analyse the interaction of turbulence generated far upstream with a thin elliptic-nosed solid body in uniform flow. The leading-edge stagnation point causes significant deformation of incident vorticity, and hence our analysis focuses on the region of size scaling with the nose radius close to the stagnation point. Rapid distortion theory is used to separate the flow field generated by a single unsteady gust perturbation into a convective non-acoustic part, containing the evolution of the upstream vortical disturbance, and an acoustic part generated by the interaction of the vorticity with the solid surface, as is typical in gust–aerofoil interaction theory. Using single-frequency gust response solutions, along with a von Kármán energy spectrum, we find the turbulent pressure spectrum generated by homogeneous isotropic turbulence incident from far upstream. Both high- and low-frequency gusts are considered to allow approximations to be found for the turbulent pressure spectra close to the leading edge, and far from the body close to the incident stagnation streamline. Good agreement is shown between the asymptotic results for the near- and far-field leading-edge turbulent pressure spectra and recent experimental findings.

A Subdomain Method for the Aeroacoustic Simulation of a Generic Side View Mirror

2013 ◽  
Vol 437 ◽  
pp. 321-324
Author(s):  
Li Na Huang ◽  
Ming Xin Xue ◽  
Hao Dong ◽  
Bo Yang
Keyword(s):  
Flow Field ◽  
Aerodynamic Noise ◽  
Complex Geometries ◽  
Side View ◽  
Cell Numbers ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Subdomain Method ◽  
Aeroacoustic Simulation ◽  
Good Agreement

The aerodynamic noise caused by the flow field around a generic side view mirror (SVM) was simulated using a subdomain large eddy simulation (LES) method. In this method, the LES solution could be run only in the subdomain, which can be the flow field near the SVM. The subdomain LES results show good agreement with the cited experimental data in some related works. With the principal advantage of saving CFD cell numbers, the subdomain LES method would be a perspective way to simulate the aerodynamic noise of complex geometries such as the real automobiles.

scholarly journals Effects of porous trailing edge on aerodynamic noise characteristics

2020 ◽  
Vol 19 (3-5) ◽  
pp. 254-271 ◽  
Author(s):  
Minghui Zhang ◽  
Tze Pei Chong
Keyword(s):  
High Reynolds Number ◽  
Experimental Testing ◽  
Low Frequency ◽  
Reynolds Numbers ◽  
Broadband Noise ◽  
Aerodynamic Noise ◽  
Trailing Edge ◽  
Noise Characteristics ◽  
Trailing Edges ◽  
High Reynolds

The objective of this work is to investigate the effect of the porous trailing edge on the aeroacoustics performance of the NACA 65(12)-10 aerofoil. The motivation behind this study is to investigate the effect of the porous parameters to explore the noise control concepts. Experimental testing in an aeroacoustics open jet wind tunnel was performed at chord-based Reynolds numbers between 0.2 and 0.6 million, and effective angles of attack at ±1.7 degree, including at 0 degrees. The porous trailing edge at porosity 30% with different holes diameters and the length of these porous trailing edges are used in the acoustic experiments. The study reveals that the level of the reduction of the broadband noise becomes larger as the diameter of the holes decreases and the length of the porous trailing edge increases at lower Reynolds numbers. Bluntness-induced tone noise is produced at high Reynolds number. Meanwhile, the porous trailing edge can suppress the laminar instability noise at the middle and low frequency regions.

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