Numerical Study on the Mechanism of Wind Noise Generation About a Car-Like Body

1994 ◽  
Vol 116 (3) ◽  
pp. 424-432 ◽  
Author(s):  
Ming Zhu ◽  
Yuji Hanaoka ◽  
Hideaki Miyata
Keyword(s):  
Surface Pressure ◽  
Flow Separation ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Strong Relationship ◽  
Vortical Flow ◽  
Noise Generation ◽  
Front Side ◽  
Wind Noise ◽  
Side Window

Three-dimensional flow separation about the sharp-edged front-pillar of a car-like body at high cruising speed is numerically studied. A time-dependent and full Navier-Stokes simulation is carried out for the understanding of mechanism of wind noise generation due to the vortical flow motions. The surface pressure fluctuations on the front-side window are examined in terms of wind noise, based on a simplified Lighthill-Curle’s equation. The simulated results are validated regarding the numerical grid resolution and assessed by comparison with the conventional acoustic theory. The analyses of the simulated flow-field data indicate that there is a strong relationship between the vortical motions associated with the flow separation and the surface pressure fluctuations on the front-side window. The bifurcations of flow geometry, such as the breakdown of a separated vortex as well as the vortex-vortex interaction, seem to be most strongly related to the production of surface pressure fluctuations.

Investigation into effects of side-window rubber sealer on cabin interi-or noise due to external flow disturbances of vehicle

2021 ◽  
Vol 263 (2) ◽  
pp. 4361-4367
Author(s):  
Sangheon Lee ◽  
Songjune Lee ◽  
Cheolung Cheong ◽  
Hyerin Kwon ◽  
Changman Seo
Keyword(s):  
Numerical Methods ◽  
Surface Pressure ◽  
Jet Flow ◽  
External Flow ◽  
Performance Criteria ◽  
Design Stage ◽  
Sound Insulation ◽  
Wind Noise ◽  
Side Window ◽  
Insulation Performance

Electric vehicles' rapid commercialization increases the relative importance of wind noise, especially for cabin interior noise. In this study, systematic numerical methods are developed to assess the wind noise insulation performance of side-window rubber seals in a design stage. First, the simplified automotive cabin model (SACM) is constructed to test the rubber seals' sound insulation performance due to external flow disturbance generated by jet flow. The pressure signals due to the jet flow are measured inside and outside the SACM. The difference between the two signals is used as sound insulation performance criteria, so-called insertion loss (IL). Second, a numerical methodology is developed to predict the IL. The surface pressure field on the side window due to jet flow is predicted by using the high-accurate Lattice Boltzmann Method. The predicted surface pressure fluctuations are applied as input load causing side-window vibration. The interior sound is then computed by using the calculated window vibration as input. The validity of numerical methods is confirmed by comparing the predicted results with the measured ones. Finally, the present methods' ability as a design tool is confirmed by comparing the IL of the pad-added rubber seal with that of the regular seal.

Numerical study of acoustic radiation due to a supersonic turbulent boundary layer

2014 ◽  
Vol 746 ◽  
pp. 165-192 ◽  
Author(s):  
Lian Duan ◽  
Meelan M. Choudhari ◽  
Minwei Wu
Keyword(s):  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Numerical Simulations ◽  
Surface Pressure ◽  
Free Stream ◽  
Acoustic Radiation ◽  
Numerical Study ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Spatial Coherence

AbstractDirect numerical simulations are used to examine the pressure fluctuations generated by fully developed turbulence in a Mach 2.5 turbulent boundary layer, with an emphasis on the acoustic fluctuations radiated into the free stream. Single- and multi-point statistics of computed surface pressure fluctuations show good agreement with measurements and numerical simulations at similar flow conditions. Consistent with spark shadowgraphs obtained in free flight, the quasi-homogeneous acoustic near field in the free-stream region consists of randomly spaced wavepackets with a finite spatial coherence. The free-stream pressure fluctuations exhibit important differences from the surface pressure fluctuations in amplitude, frequency content and convection speeds. Such information can be applied towards improved modelling of boundary layer receptivity in conventional supersonic facilities and, hence, enable a better utilization of transition data acquired in such wind tunnels. The predicted acoustic characteristics are compared with the limited available measurements. Finally, the numerical database is used to understand the acoustic source mechanisms, with the finding that the supersonically convecting eddies that can directly radiate to the free stream are confined to the buffer zone within the boundary layer.

Numerical Study of Unsteady Cavitating Flow in an Inducer with Omega Vortex Identification

2022 ◽  
Author(s):  
Yan Longlong ◽  
Bo Gao ◽  
Dan Ni ◽  
Ning Zhang ◽  
Wenjie Zhou
Keyword(s):  
Numerical Study ◽  
Pressure Fluctuations ◽  
Cavitating Flow ◽  
Vortical Flow ◽  
Flow Structures ◽  
Clear Correlation ◽  
Vortex Identification ◽  
Design Point ◽  
Identification Method ◽  
Unsteady Cavitating Flow

Abstract To accurately capture the behaviors of cavitation and reveal the unsteady cavitating flow mechanism, a condensate pump inducer is numerically analyzed in a separate numerical experiment with LES at critical cavitation number sind,c under the design point. Based on the new Omega vortex identification method, the correction between the flow structures and cavities is clearly illustrated. Besides, the pressure fluctuations around the inducer are analyzed. Special emphasis is put on the analysis of the interactions between the cavities, turbulent fluctuations, and vortical flow structures. The Omega vortex identification method could give an overall picture of the whole cavitating flow structures to present a clear correlation between the vortices and cavities. The results show that the shear cavitation dominant the cavitation characteristics under the design point. The pure rigid rotation region mainly concentrates at the edge of the cavities while the other sheet-like cavities near the casing walls are characterized by strong turbulence fluctuations. Besides, based on the analysis of the correlation between the cavities and flow structures, the rotating cavitation under the design point may mainly attribute to the interaction between the tip leakage vortex cavitation and the next blade.

Reduced-order modeling of pressure excitation on automotive front side window

2018 ◽  
Vol 233 (10) ◽  
pp. 2669-2683 ◽  
Author(s):  
Haidong Yuan ◽  
Zhigang Yang ◽  
Chao Xia ◽  
Qiliang Li
Keyword(s):  
Dynamic Mode Decomposition ◽  
Dynamic Mode ◽  
Front Side ◽  
Frequency Range ◽  
Wind Noise ◽  
Side Window ◽  
Reduced Order ◽  
Mode Decomposition ◽  
Window Region ◽  
Pressure Excitation

The pressure excitation on automotive front side window acts as an indicator of the unsteady flow and wind noise in the front side window region. The complex unsteady flow in this area generates a wider range of vortex structures resulting in the nonhomogeneous and complex pressure excitation on side glass. The description of the pressure field, which can consider the nonhomogeneous in the exact space, is needed to better solve the vibration and noise problems. The turbulent pressure excitation on side window was achieved by the incompressible improved delayed detached-eddy simulation, which is validated by the wind tunnel experiment. The reduced-order modeling methods, including the proper orthogonal decomposition and the dynamic mode decomposition, were employed to describe the pressure excitation on side glass. The dynamic mode decomposition modes separate the pressure excitation into three parts just corresponding to three main flow structures in the front side window region: the vortex shedding of the side mirror (lower frequency range), pedestal vortex (middle frequency range), and A-pillar vortex (higher frequency range). The turbulent pressure excitation generated by the vortex shedding of the side mirror contributes most of the vibration of the side glass and then the wind noise in the cabin in the low-frequency range. (The characteristic frequency is around 60 Hz, which is close to both the measured coincidence frequency and the theoretical derivation value.) The dynamic mode decomposition analysis with the unique and exact frequency for each mode, considering the nonhomogeneous of the pressure excitation, has potential to understand and solve the vibration and wind noise problems.

Separated flow surface pressure fluctuations and pressure-velocity correlations on prolate spheroid

AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 266-274
Author(s):  
Michael C. Goody ◽  
Roger L. Simpson ◽  
Christopher J. Chesnakas
Keyword(s):  
Surface Pressure ◽  
Pressure Fluctuations ◽  
Separated Flow ◽  
Prolate Spheroid ◽  
Flow Surface
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