Advanced Numerical Methods for the Prediction of Tonal Noise in Turbomachinery—Part II: Time-Linearized Methods

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Christian Frey ◽  
Graham Ashcroft ◽  
Hans-Peter Kersken ◽  
Christian Weckmüller
Keyword(s):  
Boundary Condition ◽  
Linear System ◽  
Near Field ◽  
Linear Equations ◽  
Time Integration ◽  
Aerodynamic Noise ◽  
Fan Noise ◽  
Rotor Stator Interaction ◽  
Complex Linear ◽  
Computational Fluid Dynamics Cfd

This is the second part of a series of two papers on unsteady computational fluid dynamics (CFD) methods for the numerical simulation of aerodynamic noise generation and propagation. It focuses on the application of linearized RANS methods to turbomachinery noise problems. The convective and viscous fluxes of an existing URANS solver are linearized and the resulting unsteady linear equations are transferred into the frequency domain, thereby simplifying the solution problem from unsteady time-integration to a complex linear system. The linear system is solved using a parallel, preconditioned general minimized residual (GMRES) method with restarts. In order to prescribe disturbances due to rotor stator interaction, a so-called gust boundary condition is implemented. Using this inhomogeneous boundary condition, one can compute the generation of the acoustic modes and their near field propagation. The application of the time-linearized methods to a modern high-bypass ratio fan is investigated. The tonal fan noise predicted by the time-linearized solver is compared to numerical results presented in the first part and to measurements.

Advanced Numerical Methods for the Prediction of Tonal Noise in Turbomachinery: Part II—Time-Linearized Methods

2012 ◽  
Author(s):  
Christian Frey ◽  
Graham Ashcroft ◽  
Hans-Peter Kersken ◽  
Christian Weckmüller
Keyword(s):  
Boundary Condition ◽  
Linear System ◽  
Near Field ◽  
Linear Equations ◽  
Time Integration ◽  
Aerodynamic Noise ◽  
Fan Noise ◽  
Rotor Stator Interaction ◽  
Complex Linear ◽  
Preconditioned Gmres

This is the second part of a series of two papers on unsteady CFD methods for the numerical simulation of aerodynamic noise generation and propagation. It focuses on the application of linearized RANS methods to turbomachinery noise problems. The convective and viscous fluxes of an existing URANS solver are linearized and the resulting unsteady linear equations are transfered into the frequency domain, thereby simplifying the solution problem from unsteady time-integration to a complex linear system. The linear system is solved using a parallel, preconditioned GMRES method with restarts. In order to prescribe disturbances due to rotor stator interaction a so-called gust boundary condition is implemented. Using this inhomogeneous boundary condition one can compute the generation of the acoustic modes and their near field progagation. The application of the time-linearized methods to a modern high-bypass ratio fan is investigated. The tonal fan noise predicted by the time-linearized solver is compared to numerical results presented in the first part and to measurements.

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.

Analysis of the Automobile’s External Aerodynamic Noise Field Characteristics Based on CAA

2011 ◽  
Vol 130-134 ◽  
pp. 58-62 ◽  
Author(s):  
Zheng Yu Zheng ◽  
Ren Xian Li
Keyword(s):  
Fluid Dynamics ◽  
Boundary Condition ◽  
Computational Fluid Dynamics ◽  
Flow Model ◽  
Noise Source ◽  
Aerodynamic Noise ◽  
Dipole Source ◽  
Noise Field ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Pressure

This paper dwelled on the principle of Computational Aero-Acoustics (CAA), and utilized the Boundary Element Method (BEM) combined with the Computational Fluid Dynamics (CFD) based on Lighthill’s analogy to the automobile flow model, and converted the fluctuating flow pressure near the vehicle’s surface into the dipole source boundary condition in acoustics grid, and eventually succeeded in simulating the external aerodynamic noise field of automobile by introducing the dipole source boundary condition into the automobile’s BEM model. The distribution of vehicle’s external aero-acoustics field and the directivity of vehicle’s surface aerodynamic acoustic dipole source were also discussed carefully in this paper. The results show that: The head and tail of car are the main aerodynamic noise source radiation areas, and most of the dipole source’s SPL value is more than 70dB; the variation in car speed greatly impacts on the directivity of aerodynamic noise field near the car’s tail surface (θ=165°~195°).

Development of High Efficiency Propeller Fan for Heat-Pump Unit Using CFD and Numerical Optimization

2011 ◽  
Author(s):  
Hironobu Yamakawa ◽  
Taku Iwase ◽  
Shigehisa Funabashi ◽  
Kouichi Sakamoto ◽  
Yutaka Enokizu ◽  
...  
Keyword(s):  
Numerical Optimization ◽  
Flow Model ◽  
High Efficiency ◽  
Optimization Techniques ◽  
Aerodynamic Noise ◽  
Navier Stokes ◽  
Objective Functions ◽  
Fan Noise ◽  
Heat Pump Unit ◽  
Computational Fluid Dynamics Cfd

We developed a high-efficiency propeller fan to reduce electric power consumption of the fan motor for outdoor heatpump units, and we developed a designing tool combining computational fluid dynamics (CFD) with multi-objective optimization techniques based on the genetic algorithm (GA). In CFD, a numerical model is calculated using commercial software based on steady state, Reynolds-averaged Navier-Stokes (RANS) and k-ε turbulent flow model. The objective functions are fan efficiency and fan noise for optimization. Fan efficiency is calculated directly from the CFD results, and fan noise is calculated using an aerodynamic noise prediction model using the relative inlet and outlet velocities of the fan blades from the CFD results. We fabricated a high-efficiency propeller fan characterized with curled trailing edge tips from Pareto optimal solutions. The experimental results from the performance of the fan showed the developed fan was more efficient than conventional fan.

A Two-Phase Algorithm for the Chebyshev Solution of Complex Linear Equations

1994 ◽  
Vol 15 (6) ◽  
pp. 1440-1451
Author(s):  
Dirk P. Laurie ◽  
Lucas M. Venter
Keyword(s):  
Linear Equations ◽  
Two Phase ◽  
Complex Linear

scholarly journals FDTD Computation of Space/Time Integrated Electromagnetic Lagrangian: New Insights on Mutually Coupled Wide-band Antenna Design

2021 ◽  
Author(s):  
Debdeep Sarkar ◽  
Yahia Antar
Keyword(s):  
Electromagnetic Interference ◽  
Interference Mitigation ◽  
Near Field ◽  
Time Integration ◽  
Wide Band ◽  
Space Time ◽  
Ultra Wideband ◽  
Mimo Antennas ◽  
Electric And Magnetic Fields ◽  
Spatio Temporal

In this paper, we develop a formalism based on either spatially or temporally integrated electromagnetic (EM) Lagrangian, which provides new insights about the near-field reactive energy around generic antennas for arbitrary spatio-temporal excitation signals. Using electric and magnetic fields calculated via FDTD technique and interpolation routines, we compute and plot the normalized values of space/time integrated EM Lagrangian around antennas. While the time-integration of EM Lagrangian sheds light onto the spatial distribution of inductive/capacitive reactive energy, time-variation of spatially integrated EM Lagrangian can help in design of ultra-wideband (UWB) MIMO antennas with low mutual coupling. The EM Lagrangian approach can assist in design of energy harvesting and wireless power transfer systems, as well as for electromagnetic interference mitigation applications.

scholarly journals Development of an Improved LMD Method for the Low-Frequency Elements Extraction from Turbine Noise Background

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 805
Author(s):  
Lida Liao ◽  
Bin Huang ◽  
Qi Tan ◽  
Kan Huang ◽  
Mei Ma ◽  
...  
Keyword(s):  
Renewable Energy ◽  
Wind Turbine ◽  
Condition Monitoring ◽  
Renewable Energy Sources ◽  
Near Field ◽  
Low Frequency ◽  
Aerodynamic Noise ◽  
Frequency Noise ◽  
Human Society ◽  
Noise Background

Given the prejudicial environmental effects of fossil-fuel based energy production, renewable energy sources can contribute significantly to the sustainability of human society. As a clean, cost effective and inexhaustible renewable energy source, wind energy harvesting has found a wide application to replace conventional energy productions. However, concerns have been raised over the noise generated by turbine operating, which is helpful in fault diagnose but primarily identified for its adverse effects on the local ecosystems. Therefore, noise monitoring and separation is essential in wind turbine deployment. Recent developments in condition monitoring provide a solution for turbine noise and vibration analysis. However, the major component, aerodynamic noise is often distorted in modulation, which consequently affects the condition monitoring. This study is conducted to explore a novel approach to extract low-frequency elements from the aerodynamic noise background, and to improve the efficiency of online monitoring. A framework built on the spline envelope method and improved local mean decomposition has been developed for low-frequency noise extraction, and a case study with real near-field noises generated by a mountain-located wind turbine was employed to validate the proposed approach. Results indicate successful extractions with high resolution and efficiency. Findings of this research are also expected to further support the fault diagnosis and the improvement in condition monitoring of turbine systems.

A Numerical Study of the Blade Passing Frequency Noise of a Centrifugal Fan

2012 ◽  
Author(s):  
Jian-Cheng Cai ◽  
Da-Tong Qi ◽  
Yong-Hai Zhang
Keyword(s):  
Pressure Fluctuation ◽  
Sound Radiation ◽  
Aerodynamic Noise ◽  
Sound Power ◽  
Centrifugal Fan ◽  
Structural Noise ◽  
Tonal Noise ◽  
Fan Noise ◽  
Blade Passing Frequency ◽  
Dipole Sources

Tonal noise constitutes the major part of the overall fan noise, especially the blade passing frequency (BPF) noise which is generally the most dominant component. This paper studies the BPF tonal noise of a centrifugal fan, including the blade noise, casing aerodynamic noise, and casing structural noise caused by the flow-induced casing vibration. Firstly, generation mechanism and propagation process of fan noise were discussed and the measured spectra of fan noise and casing vibration were presented. Secondly, a fully 3-D transient simulation of the internal flow field of the centrifugal fan was carried out by the computational fluid dynamics (CFD) approach. The results revealed that the flow interactions between the impeller and the volute casing caused periodic pressure fluctuations on the solid walls of the impeller and casing. This pressure fluctuation induces aerodynamic noise radiation as dipole sources, as well as structural vibration as force excitations. Thirdly, using the acoustic analogy theory, the aeroacoustic dipole sources on the casing and blade surface were extracted. The BPF casing and blade aerodynamic sound radiation were solved by the boundary element method (BEM) taking into account the scattering effect of the casing structure. Finally, the casing structural noise was studied. The casing forced vibration and sound radiation under the excitation of BPF pressure fluctuation were calculated by finite element method (FEM) and BEM, respectively. The result indicates that at the studied flow rate, the sound power levels of the casing aerodynamic noise, blade aerodynamic noise and casing structural noise are 103 dB, 91 dB and 79 dB with the reference sound power of 1×10−12 W, respectively.

On the generation of sound by turbulent boundary layer flow over a rough wall

1984 ◽  
Vol 395 (1809) ◽  
pp. 247-263 ◽  
Keyword(s):  
Boundary Layer ◽  
Near Field ◽  
Spectral Characteristics ◽  
Rigid Wall ◽  
Control Surface ◽  
Aerodynamic Noise ◽  
Stream Velocity ◽  
Main Stream ◽  
Wall Roughness ◽  
Boundary Layer Turbulence

The production of sound by scattering of the near field of low Mach number boundary-layer turbulence by a rough, rigid wall is examined on the basis of Lighthill’s theory ( Proc. R. Soc. Lond . A 211, 564 (1952)) of aerodynamic noise. The radiation is expressed in terms of the turbulence pressure spectrum on a control surface that is parallel to the mean plane of the wall and at a stand-off distance equal to the height of the wall roughness elements, the surface irregularities being modelled by a distribution of hemispherical bosses on an otherwise plane wall. The intensity of the sound produced by unit area of the wall varies as the sixth power of the main stream velocity and, for given wall roughness, increases as the boundary-layer thickness decreases. These conclusions are in accord with experimental observations reported by Hersh { AIAA paper no. 83-0786) of the generation of high frequency sound by turbulent flow from sand-roughened pipes, and it is shown how, for moderately rough pipes, the theory reproduces the spectral characteristics of Hersh’s data.

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