Download or read book Rotor Broadband Noise Prediction with Comparison to Model Data written by Thomas F. Brooks and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A model for rotor broadband noise prediction written by Qidou Zhou and published by . This book was released on 2004 with total page 199 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theory for Broadband Noise of Rotor and Stator Cascades with Inhomogeneous Inflow Turbulence Including Effects of Lean and Sweep written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-11 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: The problem of broadband noise generated by turbulence impinging on a downstream blade row is examined from a theoretical viewpoint. Equations are derived for sound power spectra in terms of 3 dimensional wavenumber spectra of the turbulence. Particular attention is given to issues of turbulence inhomogeneity associated with the near field of the rotor and variations through boundary layers. Lean and sweep of the rotor or stator cascade are also handled rigorously with a full derivation of the relevant geometry and definitions of lean and sweep angles. Use of the general theory is illustrated by 2 simple theoretical spectra for homogeneous turbulence. Limited comparisons are made with data from model fans designed by Pratt & Whitney, Allison, and Boeing. Parametric studies for stator noise are presented showing trends with Mach number, vane count, turbulence scale and intensity, lean, and sweep. Two conventions are presented to define lean and sweep. In the "cascade system" lean is a rotation out of its plane and sweep is a rotation of the airfoil in its plane. In the "duct system" lean is the leading edge angle viewing the fan from the front (along the fan axis) and sweep is the angle viewing the fan from the side (, perpendicular to the axis). It is shown that the governing parameter is sweep in the plane of the airfoil (which reduces the chordwise component of Mach number). Lean (out of the plane of the airfoil) has little effect. Rotor noise predictions are compared with duct turbulence/rotor interaction noise data from Boeing and variations, including blade tip sweep and turbulence axial and transverse scales are explored.Hanson, Donald B.Glenn Research CenterINTERACTIONAL AERODYNAMICS; ROTORS; STATORS; CASCADE FLOW; TURBOFAN ENGINES; HOMOGENEOUS TURBULENCE; NOISE PREDICTION; ENGINE NOISE; POWER SPECTRA; LEADING EDGES; DUCTS; BROADBAND; BLADE TIPS; AIRFOILS; BOUNDARY LAYERS; MACH NUMBER; SWEEP ANGLE
Download or read book A Study of Rotor Broadband Noise Mechanisms and Helicopter Tail Rotor Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rotor broadband noise mechanisms considered are the following: (1) lift fluctuation due to turbulence ingestion; (2) boundary layer/trailing edge interaction; (3) tip vortex formation; and (4) turbulent vortex shedding from blunt trailing edge. Predictions show good agreement with available experimental data. The study shows that inflow turbulence is the most important broadband noise source for typical helicopters' main rotors at low- and mid-frequencies. Due to the size difference, isolated helicopter tail rotor broadband noise is not important compared to the much louder main rotor broadband noise. However, the inflow turbulence noise from a tail rotor can be very significant because it is operating in a highly turbulent environment, ingesting wakes from upstream components of the helicopter. The study indicates that the main rotor turbulent wake is the most important source of tail rotor broadband noise. The harmonic noise due to ingestion of main rotor tip vortices is studied. Chou, Shau-Tak Rudy Unspecified Center AERODYNAMIC NOISE; AIRCRAFT NOISE; BROADBAND; HELICOPTER TAIL ROTORS; HELICOPTERS; NOISE GENERATORS; ROTARY WINGS; ROTOR AERODYNAMICS; BLUNT TRAILING EDGES; HARMONIC OSCILLATION; NOISE PREDICTION (AIRCRAFT); TURBULENT WAKES; VORTEX SHEDDING; VORTICES...
Download or read book Broadband Rotor Noise Analyses written by Albert R. George and published by . This book was released on 1984 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Predictions of Rotor Broadband Noise written by Jason D.M. Botha and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Noise of a Model Helicopter Rotor Due to Ingestion of Turbulence written by Robert W. Paterson and published by . This book was released on 1979 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Time Varying Rotor Noise Computations and Analysis of Electric Vertical Take Off and Landing Aircraft written by Ze Feng Gan and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis makes contributions to two important aspects of computing the time-varying rotor noise of electrical vertical take-off and landing (eVTOL) aircraft for urban air mobility (UAM) applications: the time variation of rotor broadband noise, and noise due continuously-varying rotor angular speed. The noise prediction software PSU-WOPWOP was updated to compute the broadband noise spectrum as a function of observer time within a rotor period. Time-varying broadband noise spectra and directivity computations for helicopter main rotors in forward flight show significant modulation with the blade passage frequency, due to convective amplification and retarded-time effects. Qualitative agreement between noise predictions and flight test data was obtained. The noise prediction software PSU-WOPWOP was also updated to compute the discrete frequency noise of rotors with continuously-varying rotational speed, which may require accepting input kinematics and aerodynamic loading data at unevenly-spaced source time intervals. Order of magnitude analysis and numerical simulations demonstrated that thickness noise modulations caused by variable rotor speed are primarily due to the time variation of instantaneous rotor speed, rather than angular acceleration, for typical rotor speed variations expected for manned eVTOL aircraft.
Download or read book Broadband Noise Prediction for Subsonic Prop Fans written by Michel-Olivier Petithomme and published by . This book was released on 1993 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Towards Computational Aeroacoustics Prediction of Realistic Turbofan Broadband Noise Using Synthetic Turbulence Modeling written by Adrian Sescu and published by . This book was released on 2011 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: The prediction of broadband noise radiating from realistic turbulent flows interacting with complex geometries, using nonlinear time-domain algorithms, is still in infancy. The main obstacle is related to the computational efficiency--both in terms of processing time and storage capacity--but equally important is the accuracy of imposing realistic turbulence superposed on deterministic vortical gusts at the inflow boundary, or the initiation of the solution with a realistic turbulent flow. The main objective of this thesis is to derive a divergence-free synthetic turbulence model, and to impose turbulent wakes at the inflow boundary, for the prediction of broadband noise radiating from the interaction between rotor wakes and stator vanes in a realistic bypass turbofan engine. The tool is an advanced Computational Aeroacoustics code, NASA Broadband Aeroacoustic Stator Simulation (BASS) code, which employs state-of-the-art spatial and temporal schemes, and accurate boundary conditions. A number of synthetic turbulence models have been implemented in BASS code, including a new divergence free model based on the assumption that turbulence can be considered as a superposition of random eddies satisfying certain conditions. The divergence free condition is satisfied by using a streamfunction which is a scalar in two dimensions and a vector in three dimensions, and the momentum equations linearized about the mean flow. The synthetic turbulence model uses the statistics from the experimental turbulent data taken from NASA Source Diagnostic Test rig. The thesis also includes the derivation and analysis of the multidimensional finite difference schemes designed to improve the isotropy of waves propagating in multidimensions. The dispersion properties of the schemes in multidimensions are analyzed using Fourier analysis, and the isotropy error is found to be very low. The stability of the multidimensional schemes in combination with either linear multistep time marching methods and Runge-Kutta schemes are extensively analyzed. Various test cases in two or three dimensions show that the multidimensional schemes have low isotropy error, and perform more efficiently when compared to corresponding conventional schemes. The thesis begins with a thorough introduction on turbofan broadband noise prediction techniques, including a comprehensive literature review on turbofan noise and synthetic turbulence modeling. In chapter 2, an overview of Computational Aeroacoustics is included, with a description of actual fields of research, and available tools and techniques. Here, the derivation and analysis of multidimensional finite difference schemes in terms of isotropy error and stability are also included. In chapter 3, the nonlinear time-domain analysis tool, BASS code, is described, and the description and derivation of the new synthetic turbulence model are included. Chapter 4 is reserved to various results from different tests cases, and chapter 5 to comments, conclusions and remarks on future directions related to the research in this thesis.
Download or read book Airfoil Self Noise and Prediction written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: A prediction method is developed for the self-generated noise of an airfoil blade encountering smooth flow. The prediction methods for the individual self-noise mechanisms are semiempirical and are based on previous theoretical studies and data obtained from tests of two- and three-dimensional airfoil blade sections. The self-noise mechanisms are due to specific boundary-layer phenomena, that is, the boundary-layer turbulence passing the trailing edge, separated-boundary-layer and stalled flow over an airfoil, vortex shedding due to laminar boundary layer instabilities, vortex shedding from blunt trailing edges, and the turbulent vortex flow existing near the tip of lifting blades. The predictions are compared successfully with published data from three self-noise studies of different airfoil shapes. An application of the prediction method is reported for a large scale-model helicopter rotor, and the predictions compared well with experimental broadband noise measurements. A computer code of the method is given. Brooks, Thomas F. and Pope, D. Stuart and Marcolini, Michael A. Langley Research Center AEROACOUSTICS; AERODYNAMIC NOISE; AIRFOIL PROFILES; AIRFOILS; BLADE-VORTEX INTERACTION; BOUNDARY LAYER SEPARATION; BOUNDARY LAYERS; NOISE PREDICTION (AIRCRAFT); VORTEX SHEDDING; AERODYNAMIC STALLING; APPLICATIONS PROGRAMS (COMPUTERS); NOISE MEASUREMENT; NOISE SPECTRA; ROTARY WINGS; STROUHAL NUMBER; TRAILING EDGES; VORTICES; WIND TUNNEL TESTS...
Download or read book Rotorcraft Aeromechanics written by Wayne Johnson and published by Cambridge University Press. This book was released on 2013-04-29 with total page 949 pages. Available in PDF, EPUB and Kindle. Book excerpt: A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.
Download or read book NASA Reference Publication written by and published by . This book was released on 1977 with total page 800 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Airfoil Self noise and Prediction written by Thomas F. Brooks and published by . This book was released on 1989 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Open Rotor Aeroacoustic Modeling written by Edmane Envia and published by BiblioGov. This book was released on 2013-06 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Owing to their inherent fuel efficiency, there is renewed interest in developing open rotor propulsion systems that are both efficient and quiet. The major contributor to the overall noise of an open rotor system is the propulsor noise, which is produced as a result of the interaction of the airstream with the counter-rotating blades. As such, robust aeroacoustic prediction methods are an essential ingredient in any approach to designing low-noise open rotor systems. To that end, an effort has been underway at NASA to assess current open rotor noise prediction tools and develop new capabilities. Under this effort, high-fidelity aerodynamic simulations of a benchmark open rotor blade set were carried out and used to make noise predictions via existing NASA open rotor noise prediction codes. The results have been compared with the aerodynamic and acoustic data that were acquired for this benchmark open rotor blade set. The emphasis of this paper is on providing a summary of recent results from a NASA Glenn effort to validate an in-house open noise prediction code called LINPROP which is based on a high-blade-count asymptotic approximation to the Ffowcs-Williams Hawkings Equation. The results suggest that while predicting the absolute levels may be difficult, the noise trends are reasonably well predicted by this approach.
Download or read book Rotorcraft Noise written by and published by . This book was released on 1982 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of an Improved Design Tool for Predicting and Simulating Helicopter Rotor Noise written by H. Kevin Johnson and published by . This book was released on 1974 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rotor noise prediction program has been improved by the following items: (1) inclusion of the helicopter rotor noise ground reflection phenomenon, (2) inclusion of the variability of oscillatory forces as related to the vortex shedding phenomenon, (3) expansion of the data base for the broadband noise data bank, and (4) description of a calculation procedure which demonstrates how the program input deck can be modified to account for impulse signals of single-rotor blade vortex interactions. The rotor noise prediction program has been developed so that the acoustic characteristics of new, untested rotor designs could be evaluated as well as the effects of basic design changes on the acoustic signature of existing rotors. (Modified author abstract).
