Computation of vortical flow and flow induced noise by large eddy simulation with FW-H acoustic analogy and Powell vortex sound theory

2016 ◽  
Vol 28 (2) ◽  
pp. 255-266 ◽  
Author(s):  
Nan Zhang ◽  
Hua Xie ◽  
Xing Wang ◽  
Bao-shan Wu
Keyword(s):  
Large Eddy Simulation ◽  
Vortical Flow ◽  
Acoustic Analogy ◽  
Vortex Sound ◽  
Eddy Simulation ◽  
Sound Theory ◽  
Large Eddy ◽  
Flow Induced Noise

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.

Wake-Airfoil Interaction as Broadband Noise Source: A Large-Eddy Simulation Study

2005 ◽  
Vol 4 (1-2) ◽  
pp. 93-115 ◽  
Author(s):  
Jérôme Boudet ◽  
Nathalie Grosjean ◽  
Marc C. Jacob
Keyword(s):  
Large Eddy Simulation ◽  
Particle Image ◽  
Broadband Noise ◽  
Far Field ◽  
Acoustic Analogy ◽  
Eddy Simulation ◽  
Naca0012 Airfoil ◽  
Image Velocimetry ◽  
Large Eddy ◽  
Proper Orthogonal

A large-eddy simulation is carried out on a rod-airfoil configuration and compared to an accompanying experiment as well as to a RANS computation. A NACA0012 airfoil (chord c = 0.1 m) is located one chord downstream of a circular rod (diameter d = c/10, Red = 48 000). The computed interaction of the resulting sub-critical vortex street with the airfoil is assessed using averaged quantities, aerodynamic spectra and proper orthogonal decomposition (POD) of the instantaneous flow fields. Snapshots of the flow field are compared to particle image velocimetry (PIV) data. The acoustic far field is predicted using the Ffowcs Williams & Hawkings acoustic analogy, and compared to the experimental far field spectra. The large-eddy simulation is shown to accurately represent the deterministic pattern of the vortex shedding that is described by POD modes 1 & 2 and the resulting tonal noise also compares favourably to measurements. Furthermore higher order POD modes that are found in the PIV data are well predicted by the computation. The broadband content of the aerodynamic and the acoustic fields is consequently well predicted over a large range of frequencies ([0 kHz; 10 kHz]).

Large Eddy Simulation of the Flow Around a Diffuser-Equipped Bluff Body in Ground Effect

2011 ◽  
Author(s):  
Lara Schembri Puglisevich ◽  
Gary Page
Keyword(s):  
Large Eddy Simulation ◽  
Bluff Body ◽  
Vortex Formation ◽  
Ground Effect ◽  
Vortical Flow ◽  
Navier Stokes ◽  
Flow Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Features

Unsteady Large Eddy Simulation (LES) is carried out for the flow around a bluff body equipped with an underbody rear diffuser in close proximity to the ground, representing an automotive diffuser. The goal is to demonstrate the ability of LES to model underbody vortical flow features at experimental Reynolds numbers (1.01 × 106 based on model height and incoming velocity). The scope of the time-dependent simulations is not to improve on Reynolds-Averaged Navier Stokes (RANS), but to give further insight into vortex formation and progression, allowing better understanding of the flow, hence allowing more control. Vortical flow structures in the diffuser region, along the sides and top surface of the bluff body are successfully modelled. Differences between instantaneous and time-averaged flow structures are presented and explained. Comparisons to pressure measurements from wind tunnel experiments on an identical bluff body model shows a good level of agreement.

scholarly journals Numerical study of a control scheme on flow-induced cavity noise

2019 ◽  
Vol 283 ◽  
pp. 09002
Author(s):  
Lulu Liu ◽  
Jin Liu ◽  
Shijin Lyu
Keyword(s):  
Experimental Data ◽  
Cavity Length ◽  
Numerical Study ◽  
Numerical Procedure ◽  
Acoustic Analogy ◽  
Cavity Depth ◽  
Eddy Simulation ◽  
Control Scheme ◽  
Large Eddy ◽  
Flow Induced Noise

A numerical procedure for flow induced cavity noise is established in the paper. The procedure is based on large eddy simulation and FW-H acoustic analogy. The computational scheme is validated by comparing with experimental data. The change of flow induced noise along with cavity length, cavity depth and velocity is studied. A noise control scheme, which includes upright grille and oblique grille, is designed for reducing the flow-induced cavity noise. It turns out that the oblique grille shows superiority in the reduction of cavity noise by modifying the flow structure of the sheat layer.

Large Eddy Simulation of a Vortex Ring Impacting a Bump

2014 ◽  
Vol 6 (3) ◽  
pp. 261-280
Author(s):  
Heng Ren ◽  
Ning Zhao ◽  
Xi-Yun Lu
Keyword(s):  
Large Eddy Simulation ◽  
Vortex Ring ◽  
Three Dimensional ◽  
Vortical Flow ◽  
Flow State ◽  
Vortical Structures ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Flow Phenomena ◽  
Flow Evolution

AbstractA vortex ring impacting a three-dimensional bump is studied using large eddy simulation for a Reynolds number Re = 4 × 104 based on the initial diameter and translational speed of the vortex ring. The effects of bump height and vortex core thickness for thin and thick vortex rings on the vortical flow phenomena and the underlying physical mechanisms are investigated. Based on the analysis of the evolution of vortical structures, two typical kinds of vortical structures, i.e., the wrapping vortices and the hair-pin vortices, are identified and play an important role in the flow state evolution. The boundary vorticity flux is analyzed to reveal the mechanism of the vorticity generation on the bump surface. The circulation of the primary vortex ring reasonably elucidates some typical phases of flow evolution. Further, the analysis of turbulent kinetic energy reveals the transition from laminar to turbulent state. The results obtained in this study provide physical insight into the understanding of the mechanisms relevant to the flow evolution and the flow transition to turbulent state.

scholarly journals Aeroacoustic noise prediction of a vertical axis wind turbine using large eddy simulation

2021 ◽  
pp. 1475472X2110551
Author(s):  
Aya Aihara ◽  
Karl Bolin ◽  
Anders Goude ◽  
Hans Bernhoff
Keyword(s):  
Large Eddy Simulation ◽  
Wind Turbine ◽  
Sound Pressure ◽  
Vertical Axis ◽  
Low Noise ◽  
Speed Ratio ◽  
Acoustic Analogy ◽  
Vertical Axis Wind Turbine ◽  
Eddy Simulation ◽  
Large Eddy

This study investigates the numerical prediction for the aerodynamic noise of the vertical axis wind turbine using large eddy simulation and the acoustic analogy. Low noise designs are required especially in residential areas, and sound level generated by the wind turbine is therefore important to estimate. In this paper, the incompressible flow field around the 12 kW straight-bladed vertical axis wind turbine with the rotor diameter of 6.5 m is solved, and the sound propagation is calculated based on the Ffowcs Williams and Hawkings acoustic analogy. The sound pressure for the turbine operating at high tip speed ratio is predicted, and it is validated by comparing with measurement. The measured spectra of the sound pressure observed at several azimuth angles show the broadband characteristics, and the prediction is able to reproduce the shape of these spectra. While previous works studying small-scaled vertical axis wind turbines found that the thickness noise is the dominant sound source, the loading noise can be considered to be a main contribution to the total sound for this turbine. The simulation also indicates that the received noise level is higher when the blade moves in the downwind than in the upwind side.

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