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Academic literature on the topic 'FW-H equation'

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Published: 1 April 2023

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Journal articles on the topic "FW-H equation"

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Kusyumov, Alexander, Sergey Mikhailov, Sergey Kusyumov, Elena Romanova, and Georgios Barakos. "Some Peculiarities of Helicopter Main Rotor Aeroacoustic for Far-Field Observer." EPJ Web of Conferences 213 (2019): 02048. http://dx.doi.org/10.1051/epjconf/201921302048.

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Mathematical models for helicopter rotor acoustics are usually based on the Ffowcs Williams–Hawkings (FW–H) equation. The level of rotor noise is determined by geometry (thickness noise) of a flying vehicle and distributed blade loading (loading noise). Initially, the FW-H equation was obtained from Euler’s equations and does not depend on the viscosity of flow. In the present work the UH-1H helicopter is considered as a test case for numerical CFD simulation and comparison to experimental data.
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Tao, Jun, Gang Sun, Ying Hu, and Miao Zhang. "Noise Prediction for Multi-Element Airfoil Based on FW-H Equation." Applied Mechanics and Materials 52-54 (March 2011): 1388–93. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.1388.

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In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.
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Najafi-Yazdi, Alireza, Guillaume A. Brès, and Luc Mongeau. "An acoustic analogy formulation for moving sources in uniformly moving media." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 467, no. 2125 (June 30, 2010): 144–65. http://dx.doi.org/10.1098/rspa.2010.0172.

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Acoustic analogy methods are used as post-processing tools to predict aerodynamically generated sound from numerical solutions of unsteady flow. The Ffowcs Williams–Hawkings (FW–H) equation and related formulations, such as Farassat’s Formulations 1 and 1A, are among the commonly used analogies because of their relative low computation cost and their robustness. These formulations assume the propagation of sound waves in a medium at rest. The present paper describes a surface integral formulation based on the convective wave equation, which takes into account the presence of a mean flow. The formulation was derived to be easy to implement as a numerical post-processing tool for computational fluid dynamics codes. The new formulation constitutes one possible extension of Farassat’s Formulation 1 and 1A based on the convective form of the FW–H equation.
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Seol, Hanshin, Cheolsoo Park, and Ki-Sup Kim. "Numerical Prediction of Marine Propeller BPF Noise Using FW-H Equation and Its Experimental Validation." Transactions of the Korean Society for Noise and Vibration Engineering 26, no. 6_spc (November 20, 2016): 705–13. http://dx.doi.org/10.5050/ksnve.2016.26.6.705.

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Lyrintzis, Anastasios S. "Surface Integral Methods in Computational Aeroacoustics—From the (CFD) Near-Field to the (Acoustic) Far-Field." International Journal of Aeroacoustics 2, no. 2 (April 2003): 95–128. http://dx.doi.org/10.1260/147547203322775498.

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A review of recent advances in the use of surface integral methods in Computational AeroAcoustics (CAA) for the extension of near-field CFD results to the acoustic far-field is given. These integral formulations (i.e. Kirchhoff's method, permeable (porous) surface Ffowcs-Williams Hawkings (FW-H) equation) allow the radiating sound to be evaluated based on quantities on an arbitrary control surface if the wave equation is assumed outside. Thus only surface integrals are needed for the calculation of the far-field sound, instead of the volume integrals required by the traditional acoustic analogy method (i.e. Lighthill, rigid body FW-H equation). A numerical CFD method is used for the evaluation of the flow-field solution in the near field and thus on the control surface. Diffusion and dispersion errors associated with wave propagation in the far-field are avoided. The surface integrals and the first derivatives needed can be easily evaluated from the near-field CFD data. Both methods can be extended in order to include refraction effects outside the control surface. The methods have been applied to helicopter noise, jet noise, propeller noise, ducted fan noise, etc. A simple set of portable Kirchhoff/FW-H subroutines can be developed to calculate the far-field noise from inputs supplied by any aerodynamic near/mid-field CFD code.
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Chen, Li, Yang Yu, and Guo Xiang Hou. "Flow-Induced Noise Radiation from the Rotational Bodies Based on Fluid Mechanics Using Hybrid Immersed Boundary Lattice-Boltzmann/FW-H Method." Applied Mechanics and Materials 345 (August 2013): 345–48. http://dx.doi.org/10.4028/www.scientific.net/amm.345.345.

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A novel study of the simulations of the flow-induced noise from the moving boundary objects using the hybrid immersed boundary lattice-Boltzmann method (IB-LBM), which is the modern useful numerical method of fluid mechanics, on the Ffowcs Williams-Hawkings (FW-H) equation is carried out. The permeable surface FW-H method has been demonstrated an effective technique of the far-field noise predication, because of its complete theories and successful applications in aeroacoustics. It usually need the information of the field near sound source. Therefore, we also adopt the effective and widely used IB-LBM to treat the interaction of the moving boundaries and the fluid, in order to simulate the near-field accurately. Some simulations are shown to test the hybrid method, including the rotational cylinder. The results prove that the hybrid IB-LBM/FW-H method can simulate the large field problems of the flow-induced noise effectively and accurately.
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Guo, H., YS Wang, F. Zhu, NN Liu, and C. Yang. "Multi-field coupling prediction for improving aeroacoustic performance of muffler based on LES and FW-H acoustic analogy methods." International Journal of Aeroacoustics 20, no. 3-4 (March 24, 2021): 414–36. http://dx.doi.org/10.1177/1475472x211005409.

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Based on the large eddy simulation (LES) and Ffowcs Williams and Hawkings (FW-H) equation, a multi-field coupling method is presented for aeroacoustic prediction of a muffler with high-speed and high-temperature exhaust gasflow. A three-dimensional finite-volume model of the muffler is established by using the LES and FW-H acoustic analogy (FW-H-AA) methods. Experimental validations of the simulated results suggest a good accuracy of the combined LES and FW-H-AA approach. Some factors influencing on noise attenuation, such as the gasflow velocity, temperature and the structural parameters of the muffler are analyzed. The results show that the aerodynamic noise and turbulent kinetic energy (TKE) are mainly attributed to the structural mutations in the muffler. The outlet sound pressure level (SPL) increases with the inlet gasflow velocity and decreases with temperature. According to the factor analysis results, the target muffler is modified by adding a fillet transition to the end of inserted tube and redesigning the structures where the TKE concentrated for improving the aerodynamic performance. In terms of the outlet SPL, the inner TKE and the backpressure of the muffler, the modified muffler is significantly improved by the maximum reductions of 3-5dB in SPL, 10–20% in TKE and 0.5–2.5 kPa in backpressure. The presented method might be extended to other kinds of muffler for aeroacoustic calculation and improvement design.
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Bozorgi, Alireza, Leonidas Siozos-Rousoulis, Seyyed Ahmad Nourbakhsh, and Ghader Ghorbaniasl. "A two-dimensional solution of the FW-H equation for rectilinear motion of sources." Journal of Sound and Vibration 388 (February 2017): 216–29. http://dx.doi.org/10.1016/j.jsv.2016.10.035.

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Huang, Zhongjie, Leonidas Siozos-Rousoulis, Tim De Troyer, and Ghader Ghorbaniasl. "Helicopter rotor noise prediction using a convected FW-H equation in the frequency domain." Applied Acoustics 140 (November 2018): 122–31. http://dx.doi.org/10.1016/j.apacoust.2018.04.040.

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Khelladi, Sofiane, and Farid Bakir. "A Consistency Test of Thickness and Loading Noise Codes Using Ffowcs Williams and Hawkings Equation." Advances in Acoustics and Vibration 2010 (July 4, 2010): 1–6. http://dx.doi.org/10.1155/2010/174361.

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The thickness noise predicted by the Ffowcs Williams and Hawkings (FW&H) equation depends on the normal velocity which is very sensitive to the meshing size. Isom showed that in far field a monopolar source is equivalent to a dipolar source induced by a uniform distribution of the load on the entire moving surface. The main objective of this paper is to determine a specific expression of Isom's thickness noise in time and frequency domains for subsonic fans. The scope of the proposed expression of Isom's thickness noise is to define a benchmark test of consistency for thickness and loading noise codes in both time and frequency domains for subsonic fans when using the free field solution of FW&H's equation.
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Conference papers on the topic "FW-H equation"

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Ianniello, S. "Quadrupole noise predictions through the FW-H equation." In 4th AIAA/CEAS Aeroacoustics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1998. http://dx.doi.org/10.2514/6.1998-2377.

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Li, Fu, Zhang Yanwu, and Wang Lingling. "Vibration Modelling of Micro Air Vehicle Based on the FW-H Equation." In 2015 Joint International Mechanical, Electronic and Information Technology Conference. Paris, France: Atlantis Press, 2015. http://dx.doi.org/10.2991/jimet-15.2015.224.

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Erwin, James P., and Neeraj Sinha. "Near and Far-Field Investigations of Supersonic Jet Noise Predictions Using a Coupled LES and FW-H Equation Method." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45210.

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The hot supersonic exhausts of gas turbine engines on military aircraft generate dangerously high noise levels. The noise levels associated with operating these engines are harmful to aircraft carrier deck personnel as well as detrimental to ship and aircraft structures. In this paper, the supersonic jet exhaust is simulated using Large Eddy Simulation (LES), and the Ffowcs Williams and Hawkings (FW-H) equation transforms the LES solution to an acoustic solution in the far-field. A Mach 1.5 laboratory jet test at United Technologies Research Center - Acoustics Research Tunnel is used as validation for the LES/FW-H method. A grid refinement study was performed with the objective of determining the requirements for accurate noise predictions. The finest grid resolution yields the best near and far-field acoustic prediction. A second LES/FW-H validation case is shown for a twin jet experiment that was performed in the anechoic chamber at University of Mississippi’s National Center for Physical Acoustics (NCPA). The LES/FW-H method is applied to the higher complexity heated twin jet with faceted nozzle profiles, demonstrating the applicability of the method over a wider range of flow regimes. The far-field noise prediction agrees very well with the NCPA experiment, including the prediction of broadband shock associated noise and jet screech.
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Wang, Zeyang, Jun Huang, and Mingxu Yi. "Research on Helicopter Rotor Acoustic Noise Prediction Method Based on Convected FW-H Equation." In 2022 8th Annual International Conference on Network and Information Systems for Computers (ICNISC). IEEE, 2022. http://dx.doi.org/10.1109/icnisc57059.2022.00163.

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Wang, Zhong-Nan, Iftekhar Z. Naqavi, Mahak Mahak, Paul Tucker, Xin Yuan, and Paul Strange. "Far Field Noise Prediction for Subsonic Hot and Cold Jets Using Large-Eddy Simulation." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-27290.

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Large eddy simulations are performed for hot and cold single stream jets with an acoustic Mach number of (Ma = Vj/a∞ = 0.875). The temperature ratio (Tj/T∞) for the hot jet is 2.7 and for the cold jet it is 1.0. Grids with 34 million points are used. The simulation results for the flow field are in encouraging agreement with the mean velocity and Reynolds stress measurements. The Ffowcs Williams-Hawkings (FW-H) equation is used to predict the far-field noise. In this study four cylindrical FW-H surfaces around the jet at various radial distances from the centreline are used. The FW-H surfaces are closed at the downstream end with multiple endplates. These endplates are at x = 25.0D – 30.0D with Δ = 0.5D apart. It is shown that surfaces close to jet get affected with pseudo sound. To avoid pseudo sound, surfaces must be placed in the irrotational region. To account for all the acoustic signals end plates are necessary. However, a simple averaging process to cancel pseudo sound at the end plates is not sufficient.
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Erwin, James P., Neeraj Sinha, and Gregory P. Rodebaugh. "Large Eddy Simulations of Supersonic Impinging Jets." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-70140.

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Supersonic impinging jet flowfields contain self-sustaining acoustic feedback features that create high levels of discrete frequency tonal noise. These types of flowfields are typically found with short takeoff and landing military aircraft as well as jet blast deflector operations on aircraft carrier decks. The US Navy has a goal to reduce the noise generated by these impinging jet configurations and is investing in computational aeroacoustics to aid in the development of noise reduction concepts. In this paper, implicit Large Eddy Simulation (LES) of impinging jet flow-fields are coupled with a far-field acoustic transformation using the Ffowcs Williams and Hawkings (FW-H) equation method. The LES solves the noise generating regions of the flow in the nearfield, and the FW-H transformation is used to predict the far-field noise. The noise prediction methodology is applied to a Mach 1.5 vertically impinging jet at a stand-off distance of five nozzle throat diameters. Both the LES and FW-H acoustic predictions compare favorably with experimental measurements. Time averaged and instantaneous flowfields are shown. A calculation performed previously at a stand-off distance of four nozzle throat diameters is revisited with adjustments to the methodology including a new grid, time integrator, and longer simulation runtime. The calculation exhibited various feedback loops which were not present before and can be attributed to an explicit time marching scheme. In addition, an instability analysis of two heated jets is performed. Tonal frequencies and instability modes are identified for the sample problems.
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Caraeni, Mirela, O. Aybay, and S. Holst. "Tandem Cylinder and Idealized Side Mirror Far-Field Noise Predictions Using DES and An Efficient Implementation of FW-H Equation." In 17th AIAA/CEAS Aeroacoustics Conference (32nd AIAA Aeroacoustics Conference). Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-2843.

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Bodling, Andrew L., and Anupam Sharma. "Implementation of the Ffowcs Williams-Hawkings Equation: Predicting the Far Field Noise From Airfoils While Using Boundary Layer Tripping Mechanisms." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83385.

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A study was done to investigate how boundary layer tripping mechanisms can affect the ability of a permeable surface FW-H solver to predict the far field noise emanating from an airfoil trailing edge. The far field noise in a baseline airfoil as well as the baseline airfoil fitted with fin let fences was analyzed. Two numerical boundary layer tripping mechanisms were implemented. The results illustrated the importance of choosing a permeable integration surface that is outside any high frequency waves emanating from the trip region. The results also illustrated the importance of choosing a boundary layer tripping mechanism that minimizes any extraneous noise so that an integration surface can be taken close to the airfoil.
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Cai, Jian-Cheng, Jie Pan, and Andrew Guzzomi. "A Numerical Study of the Unsteady Flow Field and Tonal Hydrodynamic Sound of a Centrifugal Pump." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-53163.

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In this paper, the 3-D unsteady turbulent flow inside a centrifugal pump is investigated by computational fluid dynamics (CFD) in ANSYS CFX, using Detached Eddy Simulation (DES) as the turbulence approach. The pump has a single end-suction and a single volute discharge. The impeller is semi-open (unshrouded with baseplate) and has five backswept blades and pump-out back blades. The CFD model of the pump consists of the inlet, the impeller, and the volute. A sliding mesh technique has been applied to the interfaces in order to allow unsteady interactions between the rotating impeller and the stationary parts. These unsteady interactions generate pressure fluctuations over the volute casing and blade surfaces that are hydroacoustic dipoles according to Lighthill’s acoustic analogy theory. The pressure fluctuation spectra at the volute tongue show that pressure fluctuations are generated mainly by the discrete components related to the impeller rotation at low frequencies, especially the blade-passing frequency (BPF) component. This component is approximately 1% of the reference dynamic pressure 0.5ρν22 where ν2 is the circumferential velocity at the impeller outlet. The discrete components with frequency larger than 4 times BPF are no longer obvious in the spectra. Compared to the experimental results, the CFD simulation predicts much lower amplitudes for the broad band pressure fluctuations. This is reasonable, because DES combines a classical Reynolds averaged Navier Stokes (RANS) simulation with elements of Large Eddy Simulation (LES), and both RANS and LES use average methods which filter out the high frequency fluctuations. Nevertheless, CFD is capable of accurately predict the BPF component. The pressure fluctuations on the casing and blade surfaces are extracted and modelled as the stationary and rotary dipoles, respectively, according to the Ffowcs Williams and Hawkings (FW-H) equation of the acoustic analogy theory. After Fast Fourier Transform, the spectra of the pressure fluctuations are obtained, and are used to predict the tonal hydrodynamic sound radiation at BPF and its low order harmonics. The sound radiation of casing surface dipoles is calculated by extracting the tonal components, and performing a surface integration with the fundamental solution to Helmholtz equation as the kernel. A frequency domain formulation of the FW-H equation with the moving surface dipole is employed to predict the tonal blade noise. The results from these acoustical simulations show that the sound power generated by the casing surface dipole is three orders of magnitude higher than that of the blade surface dipole, and the main hydroacoustic sources are located at the volute tongue.
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Liu, Xiaomin, Xing Wang, Hu Tang, and Guang Xi. "Performance Improvement of Multi-Blade Centrifugal Fan by Using Optimal Bionic Blade." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-70061.

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The aim of this paper is to obtain a higher flow rate and lower noise multi-blade centrifugal fan by employing a type of optimized bionic blade. The design of experiment with orthogonal array tables is used in the optimization process. The factors of the geometric parameters of the bionic blade which selected in the present study are leading edge curvature, leading edge thickness, the leading edge angle and pressure side surface curvature. The contribution of each factor to the performance of bionic blade is investigated numerically by solving Navier-Stokes equation and FW-H equation. The pressure side surface curvature of the blade is considered as the most effective factor. Compared with the original blade, the optimal bionic blade not only improve the flow rate of multi-blade centrifugal fan, but also suppress noise occurred on the blade surface effectively. The values of the flow rate and the A-weighted sound pressure level (SPL) for the fan with optimal bionic blade are 2.75m3/s, 44.9dB(A) respectively against the initial fan of 2.55m3/s, 52.4dB(A). The optimization results demonstrate considerable improvement of the multi-blade centrifugal fan in both flow rate and A-weighted SPL when the optimized bionic blade is used.
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