Research of Whirlpool Sound Radiation in Turbulence Coherent Structures

2013 ◽  
Author(s):  
Xiaosa Li ◽  
Zegang Qian ◽  
Qichao Yang
Keyword(s):  
Flow Field ◽  
Vortex Shedding ◽  
Coherent Structures ◽  
Acoustic Radiation ◽  
Unit Length ◽  
Vortex Pair ◽  
Aerodynamic Noise ◽  
Large Eddy Simulation Model ◽  
Noise Radiation ◽  
Eddy Simulation

The compressor aerodynamic noise consists of suction, exhausting noise, gas power noise and so on, and the exhausting noise is dominating. Gas which is compressed released instantaneously to form vortex injection noise and exhausting pulsation noise, yet will cause pipe vibration. Large Eddy Simulation model in fluid software FLUENT have been adopted to analyze unsteady flow field and the acoustic field and research unsteady vortex shedding and its noise radiation characteristics in compressor pipes. The results show that: the trailing edge vortex shedding phenomenon, interaction between separation vortex and the trailing vortex of downstream lead to a large gas pulsation which makes noise radiation enhanced in the compressor pipe flow field in screw compressor exhausting orifice. Combination turbulence and vortex-pair phenomena in coherent structures, based on the vortex sound equation, a mathematical model of vortex-pair acoustic radiation is established. Finally unit length sound power of the whirlpool is draw to lρ0U3M4.

Detached-Eddy Simulation of Ground Effect on the Wake of a High-Speed Train

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Chao Xia ◽  
Xizhuang Shan ◽  
Zhigang Yang
Keyword(s):  
Vortex Shedding ◽  
High Speed ◽  
Vortex Pair ◽  
Ground Effect ◽  
Longitudinal Vortex ◽  
High Speed Train ◽  
Detached Eddy Simulation ◽  
Side Force ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation

The influence of ground effect on the wake of a high-speed train (HST) is investigated by an improved delayed detached-eddy simulation. Aerodynamic forces, the time-averaged and instantaneous flow structure of the wake are explored for both the stationary ground and the moving ground. It shows that the lift force of the trailing car is overestimated, and the fluctuation of the lift and side force is much greater under the stationary ground, especially for the side force. The coexistence of multiscale vortex structures can be observed in the wake along with vortex stretching and pairing. Furthermore, the out-of-phase vortex shedding and oscillation of the longitudinal vortex pair in the wake are identified for both ground configurations. However, the dominant Strouhal number of the vortex shedding for the stationary and moving ground is 0.196 and 0.111, respectively, due to the different vorticity accumulation beneath the train. A conceptual model is proposed to interpret the mechanism of the interaction between the longitudinal vortex pair and the ground. Under the stationary ground, the vortex pair embedded in a turbulent boundary layer causes more rapid diffusion of the vorticity, leading to more intensive oscillation of the longitudinal vortex pair.

Interaction of a Steady Approach Flow and a Circular Cylinder Undergoing Forced Oscillation

1997 ◽  
Vol 119 (4) ◽  
pp. 808-813 ◽  
Author(s):  
Jianfeng Zhang ◽  
Charles Dalton
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Large Eddy Simulation Model ◽  
Drag And Lift Coefficients ◽  
Eddy Simulation ◽  
Drag And Lift

This paper presents a numerical study on the interaction of a steady approach flow and the forced transverse oscillation of a circular cylinder. The two-dimensional stream-function/vorticity formulation of the Navier-Stokes equations is solved by a semi-implicit finite-difference scheme. Calculations for flows with different amplitude (a) and frequency (fc) of the oscillation of the cylinder show a strong effect of the oscillation when fc is close to fso, the vortex shedding frequency, of the stationary cylinder. Lock-on of vortex shedding, distinct flow patterns, and increase in both drag and lift coefficients from those of a stationary cylinder are observed for Reynolds number Re = 200, a/R (R is the radius of the cylinder) from 1.0 to 2.0, fc/fso from 0.85 to 1.7. For Re = 855, a/R = 0.26, a large eddy simulation model for turbulent flow is used. The results at Re = 855 and a/R = 0.26 show that lock-on has occurred for fc/fso ≥ 0.85. The behavior of the drag and lift coefficients is seen to be influenced by the lock-on phenomenon.

Effect of an excrescence in the slat cove: Flow-field, acoustic radiation and coherent structures

2015 ◽  
Vol 44 ◽  
pp. 108-115 ◽  
Author(s):  
D.S. Souza ◽  
D. Rodríguez ◽  
L.G.C. Simões ◽  
M.A.F. Medeiros
Keyword(s):  
Flow Field ◽  
Coherent Structures ◽  
Acoustic Radiation

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.

Near-Field Noise Prediction for Landing Gear Based on Detached Eddy Simulations

2014 ◽  
Vol 472 ◽  
pp. 105-110
Author(s):  
Ning Hu ◽  
Xuan Hao ◽  
Cheng Su ◽  
Wei Min Zhang ◽  
Han Dong Ma
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Sound Pressure ◽  
Near Field ◽  
Separated Flow ◽  
Landing Gear ◽  
Aerodynamic Noise ◽  
Noise Prediction ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

A four-wheel rudimentary landing gear is studied numerically by detached eddy simulation (DES) based on the Spalart-Allmaras turbulence model. The surface sound pressure level and sound pressure spectra are calculated using the obtained unsteady flow field. The investigation shows that DES can describe the steady and unsteady properties in the flow around rudimentary landing gear. It can give reasonable results since the flow around the landing gear is a massive separated flow. The results prove the feasibility of DES type methods in massive separated unsteady flow field and aerodynamic noise prediction for landing gear, and can be used in the study of landing gear noise reduction.

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.

Prediction of flow field and aerodynamic noise of jet fan using large eddy simulation

2012 ◽  
Vol 15 (3) ◽  
pp. 253-259 ◽  
Author(s):  
S. Tomimatsu ◽  
Y. Yamade ◽  
Y. Hirokawa ◽  
N. Nishikawa
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Aerodynamic Noise ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Jet Fan

Research on Aerodynamic Noise Reduction with Non-Smooth Surfaces of Exterior Rearview Mirror Cover

2012 ◽  
Vol 430-432 ◽  
pp. 1768-1772
Author(s):  
Xin Chen ◽  
Lei Yang
Keyword(s):  
Transient Flow ◽  
Noise Spectrum ◽  
Aerodynamic Noise ◽  
Smooth Surfaces ◽  
Acoustic Model ◽  
Large Eddy Simulation Model ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Computational Fluid Dynamics Cfd ◽  
Rearview Mirror

In order to research the car interior aerodynamic noise, the non-smooth surfaces of exterior rearview mirror are studied based on computational fluid dynamics (CFD) and computational aero acoustic (CAA) method. The large eddy simulation model was used to construct transient flow field, and the FW-H acoustic model was used to analyze the aerodynamic noise generated by the exterior rearview mirror. From the comparative analysis on aerodynamic noise spectrum of every monitor point, a conclusion can be drawn that the rearview mirror with non-smooth surfaces can improve the performance of car interior aerodynamic noise.

Analysis on the Flow Passed a Pervious Cubic-Blunt Body Based on Large Eddy Simulation

2013 ◽  
Vol 353-356 ◽  
pp. 2477-2481
Author(s):  
En Li Ye ◽  
Yi Hong Zhou ◽  
Lei Ren
Keyword(s):  
Comparative Analysis ◽  
Flow Field ◽  
Large Eddy Simulation ◽  
Vortex Shedding ◽  
Blunt Body ◽  
Static Pressure ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Eddy Simulation ◽  
Large Eddy

To overcome the deficiency that model experiments are unable to take accurate measurements without damaging the structure of the fine flow fields, a large eddy simulation is employed to simulate the three dimensional structure of the flow passed a pervious cubic-blunt body at Re=2.2×104. A comparative analysis have been taken qualitatively and quantitatively between the flow passed a pervious cubic-blunt body and the flow passed a non-pervious cubic-blunt body from the aspects of the flow structure (mainly including separation and reattachment), unsteady vortex shedding, distribution of static pressure and drag coefficient, etc. Therefore, characteristics of this kind of flow field are concluded and along with a better understanding of concrete effects they bring, which can give guidance to engineering.

Experimental and Numerical Investigation of the Aerodynamic Noise Radiated From a Centrifugal Blower

2015 ◽  
Author(s):  
Jiandong Chen ◽  
Beibei Sun ◽  
Jianrun Zhang ◽  
Fei Xue ◽  
Xin Liu
Keyword(s):  
Three Dimensional ◽  
Prediction Method ◽  
Aerodynamic Noise ◽  
Centrifugal Fan ◽  
Centrifugal Blower ◽  
Fan Noise ◽  
Large Eddy Simulation Model ◽  
Scattering Effect ◽  
Eddy Simulation ◽  
Numerical Result

Centrifugal blowers are widely used as garden machines, however, the aerodynamic noise generated by these machines cause serious problems. Although many researches focus on the generation mechanism and prediction method of centrifugal fan noise, most of these researches analysis the simplified centrifugal fan models and ignore the diffraction and scattering effect. In this paper, both experimental and numerical methods are carried out to analysis and measure the aerodynamic noise of the centrifugal blower. In order to calculate the flow field, a CFD (Computational Fluid Dynamics) numerical model is established, and the LES (Large Eddy Simulation) model is used to solve the three-dimensional unsteady flow, while the FW-H (Ffows Williams-Hawkings) model is used to calculate the acoustic source. To consider the diffraction and scattering effect, a BEM method is used to predict the sound radiated from the blower. A parallel experiment is carried out to measure the aerodynamic noise in a semi-anechoic room, and the numerical result shows a good agreement with the experiment result. The effect of outlet and inlet ducts on the sound radiation of the centrifugal blower is also investigated in this paper.

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