Download or read book Trailing Edge Noise Prediction Using Large Eddy Simulation and Acoustic Analogy written by Eric Manoha and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Airfoil Aeroacoustics LES and Acoustic Analogy Predictions written by William Roberto Wolf and published by Stanford University. This book was released on 2011 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of physics-based noise prediction tools for analysis of aerodynamic noise sources is of paramount importance since noise regulations have become more stringent. Direct simulation of aerodynamic noise remains prohibitively expensive for engineering problems because of the resolution requirements. Therefore, hybrid approaches that consist of predicting nearfield flow quantities by a suitable CFD simulation and farfield sound radiation by aeroacoustic integral methods are more attractive. In this work, we apply the fast multipole method (FMM) to accelerate the solution of boundary integral equation methods such as the boundary element method (BEM) and the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation. The FMM-BEM is implemented for the solution of acoustic scattering problems and the effects of non-uniform potential flows on acoustic scattering are investigated. The FMM-FWH is implemented for the solution of two and three-dimensional problems of sound propagation. The effects of flow convection and non-linear quadrupole sources are assessed through the study of sound generated by unsteady laminar flows. Finally, a hybrid methodology is applied for the investigation of airfoil noise. This study is important for the design of aerodynamic shapes such as wings and high-lift devices, as well as wind turbine blades, fans and propellers. The present investigation of airfoil self-noise generation and propagation concerns the broadband noise that arises from the interaction of turbulent boundary layers with the airfoil trailing edge and tonal noise that arises from vortex shedding generated by laminar boundary layers. Nearfield acoustic sources are computed using compressible large eddy simulation (LES) and acoustic predictions are performed by the FMM-FWH. Numerical simulations are conducted for a NACA0012 airfoil with tripped boundary layers and blunt rounded trailing edge at different Mach numbers and angles of incidence. The effects of non-linear quadrupole sources and convection are assessed. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and excellent agreement is observed.

Download or read book LES Based Trailing Edge Noise Prediction written by W. Schroeder and published by . This book was released on 2001 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paper presents a large-eddy simulation of the flow over a sharp trailing edge. To minimize the computational effort inflow conditions for fully turbulent compressible boundary layers are developed. The LES findings show good agreement with other numerical and experimental data. For the prediction of the trailing-edge noise, acoustic perturbation equations are derived, which are excited by sources determined from results of a compressible flow simulation. Results of acoustic fields are presented for a model problem.

Download or read book Trailing Edge Noise Prediction Large Eddy Simulation of Wall Bounded Shear Flow Using the Nonlinear Disturbance Equations written by and published by . This book was released on 2000 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The potential benefits of using the Nonlinear Disturbance (NLD) equations, which govern flow variable fluctuations about an estimated mean, for the large-eddy simulation (LES) of wall bounded shear flows are investigated in this paper. In addition to verifying the suitability of the NLD equations for wall bounded flows, we build upon its advantages by introducing a new wall model that is easily and efficiently implemented within the NLD equation framework. The model implementation consists of defining a near wall region in which a modified linear set of equations are solved. The linear equation set allows disturbances to pass through and interact with the wall without altering the estimated mean. The streamwise and spanwise grid resolution of this near wall region can therefore be significantly relaxed while maintaining reasonable mean quantities such as skin friction. Comparisons of predicted turbulence intensity profiles and wall pressure spectra to experimental data for a fully developed turbulent flat plate boundary layer are used to verify the suitability of the NLD equations for wall bounded flows. Preliminary results of a turbulent channel flow simulation are also presented to assess the new wall model.

Download or read book Trailing Edge Noise Prediction Using the Non Linear Disturbance Equations written by Abhishek Jain and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: AIRFOIL self-noise consists of five major sources. One of these identified sources is turbulent boundary layer -- trailing edge (TBL-TE) noise, which is an important source of rotor and wind turbine broadband noise, and the focus of this thesis. Trailing edge noise is the result of unsteady flow interacting with the trailing edge of an airfoil or other sharp edged flow surface. The presence of the sharp trailing edge scatters the sound generated by the turbulent eddies very efficiently, especially for sources in the immediate vicinity of the edge. There is a need for accurate and computationally efficient methods to calculate the turbulent boundary layer trailing-edge (TBL-TE) noise that are not reliant on empirical data. The majority of the current semi-empirical techniques are based on measurements from symmetric NACA airfoil sections (i.e. NACA 0012). These techniques are generally not coupled with CFD solvers to obtain turbulent boundary layer data that provides pertinent parameters used in the acoustic calculations. Some methods exist that incorporate CFD solutions like Large Eddy simulations (LES) into their noise prediction algorithms. But these are prohibitively expensive and impractical for routine use. The method described in this paper is a first principles approach that aims to predict the TBL-TE noise using computational aeroacoustic (CAA) techniques without resorting to empiricism.The prediction of trailing edge noise requires an accurate calculation of the boundary layer fluctuations in the vicinity of the trailing edge. Scales in the computational domain ranging from the small turbulent boundary layer scales to those of the long-range noise propagation need to be resolved. These data can be obtained using simulation techniques like Direct Numerical Simulation (DNS) or Large Eddy Simulation (LES). However such simulations for complete helicopters or wind turbine rotors are impractical given today's computational resources. Also, DNS becomes unrealistic for the propagation of the acoustic signal to distant observers. The method described here overcomes these limitations by using a hybrid CAA approach coupled with a flow solver based on the non-linear disturbance equations (NLDE). The overall problem is separated into component problems with the NLDE equations applied over a relatively small noise generating region i.e. approximately the last 10% of the chord or less. This makes the solution more computationally efficient than LES for the full airfoil or rotor and enables the use of the most computationally efficient methods in the required regions. The proposed method is advantageous to helicopter and wind turbine manufacturers as it provides a tool for the prediction of rotor broadband noise at the design stage. This can also be used as a tool to reduce noise through the analysis of appropriate noise reduction devices.

Download or read book Large Eddy Simulation for Acoustics written by Claus Wagner and published by Cambridge University Press. This book was released on 2007-01-15 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: Noise around airports, trains, and industries attracts environmental concern and regulation. Large-eddy simulation (LES) is used for noise-reduced design and acoustical research. This 2007 book, by 30 experts, presents the theoretical background of acoustics and LES, and details about numerical methods, e.g. discretization schemes, boundary conditions, and coupling aspects.

Download or read book Wall modeled Large eddy Simulations for Trailing edge Turbulent Boundary Layer Noise Prediction written by Thomas Malkus and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Large Eddy Simulation for Incompressible Flows written by P. Sagaut and published by Springer Science & Business Media. This book was released on 2006 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."

Download or read book Airfoil Aeroacoustics LES and Acoustic Analogy Predictions written by William Roberto Wolf and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of physics-based noise prediction tools for analysis of aerodynamic noise sources is of paramount importance since noise regulations have become more stringent. Direct simulation of aerodynamic noise remains prohibitively expensive for engineering problems because of the resolution requirements. Therefore, hybrid approaches that consist of predicting nearfield flow quantities by a suitable CFD simulation and farfield sound radiation by aeroacoustic integral methods are more attractive. In this work, we apply the fast multipole method (FMM) to accelerate the solution of boundary integral equation methods such as the boundary element method (BEM) and the Ffowcs Williams & Hawkings (FWH) acoustic analogy formulation. The FMM-BEM is implemented for the solution of acoustic scattering problems and the effects of non-uniform potential flows on acoustic scattering are investigated. The FMM-FWH is implemented for the solution of two and three-dimensional problems of sound propagation. The effects of flow convection and non-linear quadrupole sources are assessed through the study of sound generated by unsteady laminar flows. Finally, a hybrid methodology is applied for the investigation of airfoil noise. This study is important for the design of aerodynamic shapes such as wings and high-lift devices, as well as wind turbine blades, fans and propellers. The present investigation of airfoil self-noise generation and propagation concerns the broadband noise that arises from the interaction of turbulent boundary layers with the airfoil trailing edge and tonal noise that arises from vortex shedding generated by laminar boundary layers. Nearfield acoustic sources are computed using compressible large eddy simulation (LES) and acoustic predictions are performed by the FMM-FWH. Numerical simulations are conducted for a NACA0012 airfoil with tripped boundary layers and blunt rounded trailing edge at different Mach numbers and angles of incidence. The effects of non-linear quadrupole sources and convection are assessed. In order to validate the numerical solutions, flow simulation and acoustic prediction results are compared to experimental data available in the literature and excellent agreement is observed.

Download or read book Large Eddy Simulation for Incompressible Flows written by Pierre Sagaut and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."

Download or read book Direct and Large Eddy Simulation IV written by Bernard Geurts and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the 2001 DLES4 workshop. It describes and discusses state-of-the-art modeling and simulation approaches for complex flows. Fundamental turbulence and modeling issues but also elements from modern numerical analysis are at the heart of this field of interest.

Download or read book Wind Turbine Noise written by Siegfried Wagner and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the last five years an enormous number of wind turbines have been installed in Europe, bringing wind energy into public awareness. However, its further development is restricted mainly by public complaints caused by visual impact and noise. The European Commission has therefore funded a number of research projects in the field of wind turbine noise within the JOULE program. This book presents the most relevant results of these projects. The book addresses all relevant aspects of wind turbine noise, namely: noise reduction, noise propagation, noise measurement, and an introduction to aeroacoustics. It may serve as a first reference in the field of wind turbine noise for researchers, planners, and manufacturers.

Download or read book Large Eddy Simulation of Airfoil Self noise written by Joseph George Kocheemoolayil and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Sustaining the continued growth of aviation is critically dependent on managing its noise emission. Developing tools to predict airframe noise from first principles is a pacing item in this regard. Within this context, noise generated by flow past airfoils constitutes an important canonical problem that is also relevant to a wide variety of other applications such as wind turbine noise, cooling fan noise, turbofan noise, propeller noise and helicopter blade noise. The noise generated by a turbulent flow that encounters the trailing edge of an airfoil is the fundamental component of all these problems. Over the past 15 years, significant strides have been made towards using large eddy simulations (LES) for predicting airfoil noise from first-principles. However, they have largely been restricted to canonical configurations at low Reynolds numbers. Perhaps the restriction to low Reynolds numbers is the most serious limitation since majority of the experiments target full-scale Reynolds numbers making one-to-one comparisons impossible. This thesis focuses on extending the scope of LES based predictions to full-scale Reynolds numbers and non-canonical configurations such as the near-stall and post-stall regimes which have received very limited attention owing to their complexity. Wall-modeled large eddy simulations (WMLES) that combine LES with a model for unresolved near-wall turbulence are used to predict airfoil noise at high Reynolds numbers. The Benchmark Problems for Airframe Noise Computations (BANC) workshop is held every year as part of the AIAA/CEAS Aeroacoustics conference. Category 1 of the workshop targets airfoil trailing edge noise prediction at high Reynolds numbers relevant to engineering applications. No first-principles based approach free of empiricism and tunable coefficients has had success in this category to date. Independently validated far-field noise measurements are available for four configurations in the category. Our simulations predict trailing edge noise accurately for all four configurations. Detailed comparisons are made with dedicated experiments. Insensitivity of the simulation results to important aleatory and epistemic uncertainties is established. Resolution requirements for making accurate noise predictions using WMLES are identified through a systematic grid-refinement study. Developing the capability to predict airfoil noise for near-stall and post-stall configurations is necessary to investigate their suspected responsibility for a phenomenon known as Other Amplitude Modulation (OAM) of wind turbine noise. Predicting the flow past a wind turbine airfoil in the post-stall regime is a formidable challenge in itself. In particular, there is a school of thought that large scale three-dimensionality and extreme sensitivity to the experimental facility are inevitable and preclude the possibility of a fair comparison between simulations and measurements in this regime. However, in agreement with a recent theoretical study our simulation results indicate that the lower lift due to large scale three-dimensionality can be reproduced even in span-periodic simulations if the domain size is sufficiently large. The large span simulation predicts the pressure distribution around the airfoil with unprecedented accuracy. Successful prediction of pressure fluctuations on the airfoil surface beneath the suction side boundary layer is demonstrated in the near-stall and post-stall regimes. Previously unavailable two-point statistics of surface pressure fluctuations are documented.

Download or read book Computation of Exhaust Mixing Noise Using Large eddy Simulation Turbulence Modeling and Lighthill s Acoustic Analogy written by David Brian Schein and published by . This book was released on 2003 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Unsteady Computational Fluid Dynamics in Aeronautics written by P.G. Tucker and published by Springer Science & Business Media. This book was released on 2013-08-30 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field of Large Eddy Simulation (LES) and hybrids is a vibrant research area. This book runs through all the potential unsteady modelling fidelity ranges, from low-order to LES. The latter is probably the highest fidelity for practical aerospace systems modelling. Cutting edge new frontiers are defined. One example of a pressing environmental concern is noise. For the accurate prediction of this, unsteady modelling is needed. Hence computational aeroacoustics is explored. It is also emerging that there is a critical need for coupled simulations. Hence, this area is also considered and the tensions of utilizing such simulations with the already expensive LES. This work has relevance to the general field of CFD and LES and to a wide variety of non-aerospace aerodynamic systems (e.g. cars, submarines, ships, electronics, buildings). Topics treated include unsteady flow techniques; LES and hybrids; general numerical methods; computational aeroacoustics; computational aeroelasticity; coupled simulations and turbulence and its modelling (LES, RANS, transition, VLES, URANS). The volume concludes by pointing forward to future horizons and in particular the industrial use of LES. The writing style is accessible and useful to both academics and industrial practitioners. From the reviews: "Tucker's volume provides a very welcome, concise discussion of current capabilities for simulating and modellng unsteady aerodynamic flows. It covers the various pos sible numerical techniques in good, clear detail and presents a very wide range of practical applications; beautifully illustrated in many cases. This book thus provides a valuable text for practicing engineers, a rich source of background information for students and those new to this area of Research & Development, and an excellent state-of-the-art review for others. A great achievement." Mark Savill FHEA, FRAeS, C.Eng, Professor of Computational Aerodynamics Design & Head of Power & Propulsion Sciences, Department of Power & Propulsion, School of Engineering, Cranfield University, Bedfordshire, U.K. "This is a very useful book with a wide coverage of many aspects in unsteady aerodynamics method development and applications for internal and external flows." L. He, Rolls-Royce/RAEng Chair of Computational Aerothermal Engineering, Oxford University, U.K. "This comprehensive book ranges from classical concepts in both numerical methods and turbulence modelling approaches for the beginner to latest state-of-the-art for the advanced practitioner and constitutes an extremely valuable contribution to the specific Computational Fluid Dynamics literature in Aeronautics. Student and expert alike will benefit greatly by reading it from cover to cover." Sébastien Deck, Onera, Meudon, France

Download or read book Aeroacoustics of Low Mach Number Flows written by Stewart Glegg and published by Academic Press. This book was released on 2017-02-15 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aeroacoustics of Low Mach Number Flows: Fundamentals, Analysis, and Measurement provides a comprehensive treatment of sound radiation from subsonic flow over moving surfaces, which is the most widespread cause of flow noise in engineering systems. This includes fan noise, rotor noise, wind turbine noise, boundary layer noise, and aircraft noise. Beginning with fluid dynamics, the fundamental equations of aeroacoustics are derived and the key methods of solution are explained, focusing both on the necessary mathematics and physics. Fundamentals of turbulence and turbulent flows, experimental methods and numerous applications are also covered. The book is an ideal source of information on aeroacoustics for researchers and graduate students in engineering, physics, or applied math, as well as for engineers working in this field. Supplementary material for this book is provided by the authors on the website www.aeroacoustics.net. The website provides educational content designed to help students and researchers in understanding some of the principles and applications of aeroacoustics, and includes example problems, data, sample codes, course plans and errata. The website is continuously being reviewed and added to. Explains the key theoretical tools of aeroacoustics, from Lighthill’s analogy to the Ffowcs Williams and Hawkings equation Provides detailed coverage of sound from lifting surfaces, boundary layers, rotating blades, ducted fans and more Presents the fundamentals of sound measurement and aeroacoustic wind tunnel testing

Download or read book Aerodynamic Noise written by Tarit Bose and published by Springer Science & Business Media. This book was released on 2012-11-09 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamic Noise extensively covers the theoretical basis and mathematical modeling of sound, especially the undesirable sounds produced by aircraft. This noise could come from an aircraft’s engine—propellers, fans, combustion chamber, jets—or the vehicle itself—external surfaces—or from sonic booms. The majority of the sound produced is due to the motion of air and its interaction with solid boundaries, and this is the main discussion of the book. With problem sets at the end of each chapter, Aerodynamic Noise is ideal for graduate students of mechanical and aerospace engineering. It may also be useful for designers of cars, trains, and wind turbines.