Download or read book Computation of Rotor Noise Generation in Turbulent Flow Using Large eddy Simulation written by Junye Wang and published by . This book was released on 2017 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Simulation of Turbulent Flows and Noise Generation written by Christophe Brun and published by Springer Science & Business Media. This book was released on 2009-03-07 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large Eddy Simulation (LES) is a high-fidelity approach to the numerical simulation of turbulent flows. Recent developments have shown LES to be able to predict aerodynamic noise generation and propagation as well as the turbulent flow, by means of either a hybrid or a direct approach. This book is based on the results of two French/German research groups working on LES simulations in complex geometries and noise generation in turbulent flows. The results provide insights into modern prediction approaches for turbulent flows and noise generation mechanisms as well as their use for novel noise reduction concepts.

Download or read book Noise Produced by Turbulent Flow Into a Rotor written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-20 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analysis is presented for the calculation of noise produced by turbulent flow into a helicopter rotor. The method is based on the analysis of Amiet for the sound produced by an airfoil moving in rectilinear motion through a turbulent flow field. The rectilinear motion results are used in a quasi-steady manner to calculate the instantaneous spectrum of the rotor noise at any given rotor position; the overall spectrum is then found by averaging the instantaneous spectrum over all rotor azimuth angles. Account is taken of the fact that the rotor spends different amounts of retarded time at different rotor positions. Blade to blade correlation is included in the analysis, leading to harmonics of blade passing frequency. The spectrum of the turbulence entering the rotor is calculated by applying rapid distortion theory to an isotropic turbulence spectrum, assuming that the turbulence is stretched as it is pulled into the rotor. The inputs to the program are obtained from the atmospheric turbulence model and mean flow distortion calculation, described in another volume of this set of reports. The analytical basis is provided for a module which was incorporated in NASA's ROTONET helicopter noise prediction program. Amiet, R. K. Unspecified Center NAS1-17763; RTOP 505-63-51...

Download or read book A Parallel Finite Volume Algorithm for Large eddy Simulation of Turbulent Flows written by Trong T. Bui and published by . This book was released on 1998 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Noise Produced by Turbulent Flow Into a Rotor Theory Manual for Noise Calculation written by Roy K. Amiet and published by . This book was released on 1989 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Large Eddy Simulation of Sound Generation by Turbulent Reacting and Nonreacting Shear Flows written by Alireza Najafi-Yazdi and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of the present study was to investigate the mechanisms of sound generation by subsonic jets. Large eddy simulations were performed along with bandpass filtering of the flow and sound in order to gain further insight into the pole of coherent structures in subsonic jet noise generation. A sixth-order compact scheme was used for spatial discretization of the fully compressible Navier-Stokes equations. Time integration was performed through the use of the standard fourth-order, explicit Runge-Kutta scheme. An implicit low dispersion, low dissipation Runge-Kutta (ILDDRK) method was developed and implemented for simulations involving sources of stiffness such as flows near solid boundaries, or combustion. A surface integral acoustic analogy formulation, called Formulation 1C, was developed for farfield sound pressure calculations. Formulation 1C was derived based on the convective wave equation in order to take into account the presence of a mean flow...

Download or read book Flinovia Flow Induced Noise and Vibration Issues and Aspects II written by Elena Ciappi and published by Springer. This book was released on 2018-05-25 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the proceedings of the Second International Workshop on Flow Induced Noise and Vibration (FLINOVIA), which was held in Penn State, USA, in April 2016. The authors’ backgrounds represent a mix of academia, government, and industry, and several papers include applications to important problems for underwater vehicles, aerospace structures and commercial transportation. The book offers a valuable reference guide for all those working in the area of flow-induced vibration and noise. Flow induced vibration and noise (FIVN) remains a critical research topic. Even after over 50 years of intensive research, accurate and cost-effective FIVN simulation and measurement techniques remain elusive. This book gathers the latest research from some of the most prominent experts in the field. The book describes methods for characterizing wall pressure fluctuations, including subsonic and supersonic turbulent boundary layer flows over smooth and rough surfaces using computational methods like Large Eddy Simulation; for inferring wall pressure fluctuations using inverse techniques based on panel vibrations or holographic pressure sensor arrays; for calculating the resulting structural vibrations and radiated sound using traditional finite element methods, as well as advanced methods like Energy Finite Elements; for using scaling approaches to universally collapse flow-excited vibration and noise spectra; and for computing time histories of structural response, including alternating stresses.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Computational Analysis of Noise Generation by a Rotor Ingesting Turbulent Boundary Layer on an Axisymmetric Body of Revolution written by Di Zhou and published by . This book was released on 2021 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 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 Large Eddy Simulation of Transonic Flow Field in NASA Rotor 37 written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019-01-14 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current paper reports on numerical investigations on the flow characteristics in a transonic axial compressor, NASA Rotor 37. The flow field was used previously as a CFD blind test case conducted by American Society of Mechanical Engineers in 1994. Since the CFD blind-test exercise, many numerical studies on the flow field in the NASA Rotor 37 have been reported. Although steady improvements have been reported in both numerical procedure and turbulence closure, it is believed that all the important aspects of the flow field have not been fully explained with numerical studies based on the Reynolds Averaged Navier-Stokes (RANS) solution. Experimental data show large dip in total pressure distribution near the hub at downstream of the rotor at 100% rotor speed. Most original numerical solutions from the blind test exercise did not predict this total pressure deficit correctly. This total pressure deficit at the rotor exit was attributed to a hub corner flow separation by the author. Several subsequent numerical studies with different turbulence closure model also calculated this dip in total pressure rise. Also, several studies attributed this total pressure deficit to a small leakage flow coming from the hub in the test article. As the experimental study cannot be repeated, either explanation cannot be validated. The primary purpose of the current investigation is to investigate the transonic flow field with both RANS and a Large Eddy Simulation (LES). The RANS approach gives similar results presented at the original blind test exercise. Although the RANS calculates higher overall total pressure rise, the total pressure deficit near the hub is calculated correctly. The numerical solution shows that the total pressure deficit is due to a hub corner flow separation. The calculated pressure rise from the LES agrees better with the measured total pressure rise especially near the casing area where the passage shock interacts with the tip clearance vortex and flow bec

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 1048 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Noise Produced by Turbulent Flow Into a Rotor Users Manual for Atmospheric Turbulence Prediction and Mean Flow and Turbulence Contraction Prediction written by and published by . This book was released on 1989 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Renewable Energy Volume 1 Solar Wind and Hydropower written by Abdul Ghani Olabi and published by Elsevier. This book was released on 2023-04-29 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: Renewable Energy - Volume 1: Solar, Wind, and Hydropower: Definitions, Developments, Applications, Case Studies, and Modelling and Simulation is a comprehensive resource for those wanting an authoritative volume on the significant aspects of these rapidly growing renewable technologies. Providing a structured approach to the emerging technologies and advances in the implementation of solar, wind and hydro energy, the book offers the most requested and desirable practical elements for the renewable industry. Sections cover definitions, applications, modeling and analysis through case study and example. This coordinated approach allows for standalone, accessible, and functioning chapters dedicated to a particular energy source, giving researchers and engineers an important and unique consolidated source of information on all aspects of these state-of-the-art fields. Includes in-depth and up-to-date explanations for the latest developments in Solar, Wind and Hydropower Presents a uniquely, thematically arranged book with structured content that is easily accessible and usable Provides extensively illustrated and supported content, including multimedia components like short videos and slideshows for greater examples and case studies