Download or read book An Optimization Method for the Reduction of Propeller Unsteady Forces written by Thomas S. Mauther and published by . This book was released on 1988 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Based on the work of Greenblatt (1978), an enhanced optimization technique for the reduction of propeller unsteady forces and the determination of skew distributions has been developed. The current method provides an efficient propeller design tool capable of determining a variety of cubic or quadratic skew distributions, subject to constraints, which minimize the unsteady forces produced by the various harmonic components of the input wake. The original skew optimization method was extended to include higher order harmonics, and the original force calculation method was replaced by an extended version of the method developed by Thompson (1976). Calculation of forces and skew distributions associated with a representative propeller show that acceptable reduction of unsteady forces can be obtained without having to place severe restrictions on the model constraints. The problem considered herein is the generation of propeller noise due to non-uniform inflow velocity fields. This has been still is an issue of research in the area of marine propellers, and it is felt that a recently developed method of calculating unsteady forces may also be applicable in the design and analysis of aircraft propellers. Angle-of-attack fluctuations result in unsteady blade loadings and the generation of propeller noise, and the noise sources are characterized by three types of unsteady force mechanisms: a) turbulence injection; b) vortex shedding; and c) blade-rate.
Download or read book A Propeller Skew Optimization Method written by and published by . This book was released on 1987 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: A propeller operating in the turbulent wake of an axisymmetric body with appendages encounters wake non-uniformities which result in spatial and temporal fluctuations of blade angle-of-attack. These angle-of-attack fluctuations result in unsteady blade loadings and the generation of propeller noise, and the noise sources are characterized by three types of unsteady force mechanisms: a) turbulence injestion; b) vortex shedding; and c) blade-rate. The first two mechanisms typically generate continuous spectrum (broadband) radiated noise levels while blade-rate forces generate discrete frequency noise levels at various blade-passage frequencies and harmonics. This paper will address the reduction of blade-rate noise. The hull boundary layer behind an appendage is characterized by a complex velocity field typically having velocity excesses at inner radii and velocity defects at the outer radii. This type of velocity field has a complex harmonic content distribution and its effect on blade-rate noise cannot be predicted without detailed examination of the wake and the radial distribution of propeller blade forces. The reduction of blade-rate noise and thus vehicle vibration provides the motivation for the application of skew in propeller design. Keywords: Turbulence injestion, Vortex shedding, Blade passage frequencies and harmonics, Blade rate.
Download or read book AIAA 26th Aerospace Sciences Meeting written by and published by . This book was released on 1988 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Report Abstracts written by ManTech International Corporation. CADCOM. and published by . This book was released on 1980 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Reports Awareness Circular TRAC written by and published by . This book was released on 1988-06 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Calculation of Unsteady Propeller Forces and Optimization of Skew Distribution written by Kuo-Yih Chao and published by . This book was released on 1985 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reduction of Unsteady Underwater Propeller Forces Via Active Tail Articulation written by Richard Alexander James and published by . This book was released on 2006 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) Articulation at St> 0.08 also showed unsteady forces that varied with phase but the associated unsteady forces were greater than the baseline wake for all phase angles. Similar results were obtained from spectral analysis where blade rate harmonics showed decreased magnitudes for certain phase angles at St
Download or read book UNSTEADY PROPELLER FORCES written by Lawrence Monti Casellini and published by . This book was released on 1965 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt: The problem of unsteady forces on a propeller operating in a non-uniform inflow and subjected to homogeneous, isotropic turbulence has been analyzed. Methods are presented for calculating the magnitude of the unsteady forces from these two causes. The theory is applied to a free-stream propeller operating in the wake of a single strut and in a turbulent flow. The calculations include variations of strut-to-propeller spacing, number of blades and blade sweep and show how unsteady forces are affected. In the case of a turbulent inflow, force spectra and the unsteady thrust coefficient are calculated. These quantities are seen to depend on two ratios: the characteristic eddy size divided by the propeller diameter, and the characteristic eddy size divided by the propeller blade chord length. It is shown that the unsteady forces due to turbulence are of the same order of magnitude as those due to a non-uniform inflow. (Author).
Download or read book Development of a Procedure to Measure Unsteady Propeller Forces written by William Campbell Pfister and published by . This book was released on 1971 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Unsteady Forces Due to Propeller appendage Interaction written by Technical Research Group and published by . This book was released on 1962 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study is presented of the nature of the unsteady forces in the field of a propeller rotating in the vicinity of an appendage. The propeller is assumed to be one of a high aspect ratio while the appendage although of finite width is assumed to be infinitely long and thus the problem is reduced to a study of the two dimensional flow field around two flat plates. An essential feature of the analysis is that the mutual interference effects of propeller blade and appendage are taken into account. Two approaches are formulated. The rigorous method leads to a set of two simultaneous integral equations which are reduced to a single integral equation involving elliptic integrals. The simplified method employs the technique of substitution vortices which yields explicit analytic expressions for the quasi-state, apparent-mass and wake forces for both the propeller and appendage. Graphs and tables give the magnitude and variation of the propeller and appendage forces as functions of tip clearance, distance and relative size of appendage and propeller.
Download or read book NASA SP written by and published by . This book was released on 1992 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Practical Methods for Predicting Periodic Propeller Loads written by Robert J. Boswell and published by . This book was released on 1983 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Development of Numerical Methods for the Computation of Unsteady Propeller Forces written by Oddvar Frydenlund and published by . This book was released on 1978 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Unsteady Propeller Loading Measurement Correlation With Theory and Parametric Study written by Robert J. Boswell and published by . This book was released on 1968 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Objectives of the present study are to measure the unsteady forces and moments on a series of marine propellers due to circumferentially nonuniform inflow; to correlate the measured unsteady thrust and torque with calculated values, based on various proposed theories; and to investigate variation of unsteady thrust and torque over a range of pertinent parameters, using the method determined from those described to be the best available for calculating unsteady loading. Experimental blade-frequency thrust and torque were compared with values calculated by the following techniques: quasi-steady, two-dimensional unsteady, combination quasi-steady two-dimensional unsteady, and three-dimensional unsteady. The three-dimensional unsteady theory yields the best correlation with experiment; however, the numerical techniques employed breakdown for narrow-bladed propellers and for propellers with blade overlap.
Download or read book Reduction of Unsteady Underwater Propeller Forces Via Active Tail Articulation written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: By Richard A. James.
Download or read book Aeronautical Engineering written by and published by . This book was released on 1971 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA)
Download or read book Evaluation of Propeller Unsteady Force Codes for Noncavitating Conditions written by and published by . This book was released on 2005 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this investigation is to identify the best code for calculating the unsteady forces and moments on surface ship propellers during noncavitating operating conditions. The codes being evaluated are MPUF-3A and PROPCAV from the University of Texas at Austin, and PUF-2 and PUF-14 from the Massachusetts Institute of Technology. The theoretical and numerical methods used by the codes are examined, and calculations of blade forces and moments are compared to measurements for several test cases. There were few consistent trends in the comparisons of calculations to measurements, and no one code stood out as being significantly better than the others for most test cases. PUF-2 and PROPCAV were a little better on average than the other codes for predicting blade frequency thrust and torque. The codes that used an inclined shaft wake model (PUF-2IS and MPUF-3A) were not consistently better at predicting blade loads than codes that did not use an inclined shaft wake model (PUF-14 and PROPCAV), for Propellers 4661 and 5168 on inclined shafts. MPUF-3A and PROPCAV were better overall than the other codes for predicting the first harmonic amplitudes, for propellers on an inclined shaft.
