Numerical Simulation and Spectral Analysis of Pressure Fluctuations in Vehicle Aerodynamic Noise Generation

2002 ◽  
Author(s):  
Bradley D. Duncan ◽  
Raja Sengupta ◽  
Swapan Mallick ◽  
Rick Shock ◽  
D. B. Sims-Williams
Keyword(s):  
Numerical Simulation ◽  
Spectral Analysis ◽  
Pressure Fluctuations ◽  
Aerodynamic Noise ◽  
Noise Generation

Dynamics of an impinging jet. Part 2. The noise generation

1982 ◽  
Vol 116 ◽  
pp. 379-391 ◽  
Author(s):  
Nagy S. Nosseir ◽  
Chih-Ming Ho
Keyword(s):  
Coherent Structures ◽  
Near Field ◽  
Pressure Fluctuations ◽  
Aerodynamic Noise ◽  
Far Field ◽  
Noise Generation ◽  
Physical Mechanisms ◽  
Field Noise ◽  
Subsonic Jet ◽  
Jet Axis

The aerodynamic noise generated by a subsonic jet impinging on a flat plate is studied from measurements of near-field and surface-pressure fluctuations. The far-field noise measured at 90° to the jet axis is found to be generated by two different physical mechanisms. One mechanism is the impinging of the large coherent structures on the plate, and the other is associated with the initial instability of the shear layer. These two sources of noise radiate to the far field via different acoustical paths.

scholarly journals Numerical analysis of aerodynamic noise from pantograph in high-speed trains using lattice Boltzmann method

2019 ◽  
Vol 11 (7) ◽  
pp. 168781401986399 ◽  
Author(s):  
Hee-Min Noh
Keyword(s):  
Numerical Simulation ◽  
Numerical Analysis ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
High Speed ◽  
Aerodynamic Noise ◽  
Noise Generation ◽  
Noise Sources ◽  
High Speed Trains ◽  
Boltzmann Method

A pantograph in contact with a catenary for power supply is one of the major aerodynamic noise sources in high-speed trains. To reduce pantograph noise, it is essential to understand the noise generation mechanism of the pantograph. However, it is difficult to determine this mechanism through measurement. Therefore, in this study, the aerodynamic and acoustic performances of a pantograph in a high-speed train were investigated through numerical analysis using the lattice Boltzmann method. First, a real-scaled pantograph was modeled through computer-aided design. Then, the surface and volume meshes of the pantograph model were generated for simulation analysis. Numerical simulation was conducted at a speed of 300 km/h based on the lattice Boltzmann method. Based on the time derivative analysis of flow pressures, it was concluded that the panhead, joint, and base were the dominant noise sources in the pantograph. In particular, various vortexes were generated from the metalized carbon strip of the panhead. The peaks of the sound pressure level propagated from the panhead were 242, 430, and 640 Hz. The noise generation mechanism was analyzed through numerical simulation using noise characteristics.

Advanced Numerical Methods for the Prediction of Tonal Noise in Turbomachinery—Part I: Implicit Runge–Kutta Schemes

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Graham Ashcroft ◽  
Christian Frey ◽  
Kathrin Heitkamp ◽  
Christian Weckmüller
Keyword(s):  
Stokes Equations ◽  
Temporal Integration ◽  
Aerodynamic Noise ◽  
Navier Stokes ◽  
Noise Generation ◽  
Academic Problems ◽  
Tonal Noise ◽  
Navier Stokes Equations ◽  
Runge Kutta ◽  
The Stability

This is the first part of a series of two papers on unsteady computational fluid dynamics (CFD) methods for the numerical simulation of aerodynamic noise generation and propagation. In this part, the stability, accuracy, and efficiency of implicit Runge–Kutta schemes for the temporal integration of the compressible Navier–Stokes equations are investigated in the context of a CFD code for turbomachinery applications. Using two model academic problems, the properties of two explicit first stage, singly diagonally implicit Runge–Kutta (ESDIRK) schemes of second- and third-order accuracy are quantified and compared with more conventional second-order multistep methods. Finally, to assess the ESDIRK schemes in the context of an industrially relevant configuration, the schemes are applied to predict the tonal noise generation and transmission in a modern high bypass ratio fan stage and comparisons with the corresponding experimental data are provided.

scholarly journals Aeroacoustics of Silent Owl Flight

2020 ◽  
Vol 52 (1) ◽  
pp. 395-420 ◽  
Author(s):  
Justin W. Jaworski ◽  
N. Peake
Keyword(s):  
Mathematical Modeling ◽  
Noise Reduction ◽  
Current Knowledge ◽  
Foraging Strategies ◽  
Aerodynamic Noise ◽  
Noise Generation ◽  
Reduction Strategies ◽  
Noise Measurements ◽  
Modeling And Experiments ◽  
Review Current

The ability of some species of owl to fly in effective silence is unique among birds and provides a distinct hunting advantage, but it remains a mystery as to exactly what aspects of the owl and its flight are responsible for this dramatic noise reduction. Crucially, this mystery extends to how the flow physics may be leveraged to generate noise-reduction strategies for wider technological application. We review current knowledge of aerodynamic noise from owls, ranging from live owl noise measurements to mathematical modeling and experiments focused on how owls may disrupt the standard routes of noise generation. Specialized adaptations and foraging strategies are not uniform across all owl species: Some species may not have need for silent flight, or their evolutionary adaptations may not be effective for useful noise reduction for certain species. This hypothesis is examined using mathematical models and borne out where possible by noise measurements and morphological observations of owl feathers and wings.

Numerical simulation of aeroacoustic noise from landing gear and rectangular cavity

2020 ◽  
Vol 234 (7) ◽  
pp. 1259-1271
Author(s):  
Zhifei Guo ◽  
Peiqing Liu ◽  
Jin Zhang ◽  
Hao Guo
Keyword(s):  
Numerical Simulation ◽  
Low Frequency ◽  
Landing Gear ◽  
Rectangular Cavity ◽  
Cavity Resonance ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Radiation Mechanism ◽  
Ansys Fluent ◽  
Aeroacoustic Noise

This paper is aimed at researching the interaction between aeroacoustic noise radiated from a rectangular cavity (gear bay) and from landing gear. It is a complicated flow-induced noise problem, involving the nonlinear, unsteady evolution of the turbulent structure inside the airflow bypassing the landing gear and the cavity. The generation and radiation mechanism of aeroacoustic noise are also concerned. In fact, it is a problem about the nonlinear interaction between the vortices shedding from the boundary layer of bluff bodies and the cavity-limited shear layer. To simplify this issue, a two-wheel landing gear named LAGOON is chosen as the landing gear model. The unsteady flow field and aerodynamic noise from it is simulated by applying the commercial software ANSYS Fluent. Good agreement is achieved between the numerical simulation and wind tunnel measurements in terms of the aerodynamic and aeroacoustic results. According to the size of LAGOON, a simple rectangular cavity is designed as the landing gear bay. Both the cavity combined with LAGOON and the cavity alone are simulated and compared. The results show that under the blocking effect of a strut, most small pieces of vortices at the trailing edge of the cavity bottom would dissipate rather than move forward along with the backflow, leading to the correlation of cavity resonance being more contrasting and increasing its amplitude. The blockage effect induced by rear wall could also enhance the turbulence kinetic energy at the wake of the strut, thus increasing the low-frequency noise radiated from the strut and cavity.

Calculation of Aerodynamic Noise for Centrifugal Fan of Air-Conditioner

2013 ◽  
Author(s):  
Taku Iwase ◽  
Hideshi Obara ◽  
Hiroyasu Yoneyama ◽  
Yoshinobu Yamade ◽  
Chisachi Kato
Keyword(s):  
Sound Pressure ◽  
Static Pressure ◽  
Pressure Fluctuations ◽  
Coarse Grid ◽  
Aerodynamic Noise ◽  
Absolute Velocity ◽  
Centrifugal Fan ◽  
Air Conditioner ◽  
Simulation Code ◽  
Fine Grid

Flow fields in a centrifugal fan for an indoor unit of an air-conditioner were calculated with finite element method-based large eddy simulation (LES) with the aim of predicting fan performance and aerodynamic noise in this study. The numerical simulation code employed throughout the LES was called FrontFlow/blue (FFB). We compared 10M grid [coarse grid] and 60M grid [fine grid] calculation results for investigation of influence of grid resolution. In the fine grid, the number of grid elements in blade-to-blade direction, and of region between the shroud and the bell mouth increased in particular. By calculating with the fine grid, calculated distributions of absolute velocities at blade exit reasonably agreed with experimental results. Because of this, maximum absolute velocity by fine grid near hub decreased as compared to those by coarse grid. Calculated sound pressure level by fine grid was therefore smaller than that by coarse grid, and the overestimation of sound pressure was suppressed by calculating with fine grid. This decrease of the absolute velocity was a first factor for the improvement of calculation accuracy. Moreover, number of captured streaks on the blade, hub, and shroud surfaces by fine grid increased as compared to those by coarse grid. As a result, size of streak by fine grid became smaller than that by coarse grid. Static pressure fluctuations by fine grid on the blade, hub, and shroud surfaces therefore reduced as compared to those by coarse grid. Aerodynamic noise was related to static pressure fluctuations according to Curle’s equation. This reduction of static pressure fluctuations was therefore a second factor for improvement of calculation accuracy.

Aerodynamic noise numerical simulation and noise reduction study on automobile alternator

2017 ◽  
Vol 31 (5) ◽  
pp. 2047-2055 ◽  
Author(s):  
Chunrong Hua ◽  
Yadong Zhang ◽  
Dawei Dong ◽  
Bin Yan ◽  
Huajiang Ouyang
Keyword(s):  
Numerical Simulation ◽  
Noise Reduction ◽  
Aerodynamic Noise

Impact of Impeller Casing Treatment on the Acoustics of a Small High Speed Centrifugal Compressor

2018 ◽  
Author(s):  
Sidharath Sharma ◽  
Jorge García-Tíscar ◽  
John M. Allport ◽  
Martyn L. Jupp ◽  
Ambrose K. Nickson
Keyword(s):  
Centrifugal Compressor ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Operating Conditions ◽  
Aerodynamic Noise ◽  
Noise Sources ◽  
Casing Treatment ◽  
Active Research ◽  
Ported Shroud ◽  
The Impact

Ported shroud casing treatment is widely used to delay the onset of surge and thereby enhancing the aerodynamic stability of a centrifugal compressor by recirculating the low momentum fluid in the blade passage. Performance losses associated with the use of recirculation casing treatment are well established in the literature and this is an area of active research. The other, less researched aspect of the casing treatment is its impact on the acoustics of the compressor. This work investigates the impact of ported shroud casing treatment on the acoustic characteristics of the compressor. The flow in two compressor configurations viz. with and without casing treatment operating at the design operating conditions of an iso-speed line are numerically modelled and validated with experimental data from gas stand measurements. The pressure fluctuations calculated as the flow solution are used to compute the spectral signatures at multiple locations to investigate the acoustic phenomenon associated with each configuration. Propagation of the frequency content through the ducts has been estimated with the aid of method of characteristics to enhance the content coming from the compressor. Expected tonal aerodynamic noise sources such as monopole (buzz-saw tones) and dipole (Blade Pass Frequency) are clearly identified in the acoustic spectra of the two configurations. The comparison of two configurations shows higher overall levels and tonal content in the case of a compressor with ported shroud operating at design conditions due to the presence of ‘mid-tones’.

Numerical simulation of aerodynamic noise and noise reduction of range hood

2021 ◽  
Vol 175 ◽  
pp. 107806
Author(s):  
Jia-yu Huang ◽  
Kai Zhang ◽  
Hai-yun Li ◽  
An-ran Wang ◽  
Mingyue Yang
Keyword(s):  
Numerical Simulation ◽  
Noise Reduction ◽  
Aerodynamic Noise

The Application of Numerical Simulation Technology in the External Aerodynamic Noise Field of High-Speed Train

2011 ◽  
Vol 101-102 ◽  
pp. 197-201 ◽  
Author(s):  
Zhen Gyu Zheng ◽  
Ren Xian Li
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
High Speed ◽  
Aerodynamic Noise ◽  
Dipole Source ◽  
Center Line ◽  
High Speed Train ◽  
Noise Field ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Pressure

This paper utilized the Boundary Element Method (BEM) combined with the Computational Fluid Dynamics (CFD) based on Lighthill’s analogy in the high-speed train model, and converted the fluctuating flow pressure near the vehicle’s surface into the dipole source boundary condition in acoustics grid, eventually succeeded in completing the numerical simulation of aerodynamic noise field outside the high-speed train by introducing the dipole source boundary condition into the train BEM model. The results show that the main aerodynamic noise controlling area is 15-20 meters away from the track center line in the horizontal direction, and the Sound Press Level (SPL) is 63-72dB.

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