Aerodynamics of a Linear Oscillating Cascade
Aerodynamics of a Linear Oscillating Cascade

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-07-23

Total Pages: 266

ISBN-13: 9781723509063

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The steady and unsteady aerodynamics of a linear oscillating cascade are investigated using experimental and computational methods. Experiments are performed to quantify the torsion mode oscillating cascade aerodynamics of the NASA Lewis Transonic Oscillating Cascade for subsonic inlet flowfields using two methods: simultaneous oscillation of all the cascaded airfoils at various values of interblade phase angle, and the unsteady aerodynamic influence coefficient technique. Analysis of these data and correlation with classical linearized unsteady aerodynamic analysis predictions indicate that the wind tunnel walls enclosing the cascade have, in some cases, a detrimental effect on the cascade unsteady aerodynamics. An Euler code for oscillating cascade aerodynamics is modified to incorporate improved upstream and downstream boundary conditions and also the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic influence coefficient technique. The new boundary conditions are shown to improve the unsteady aerodynamic predictions of the code, and the computational unsteady aerodynamic influence coefficient technique is shown to be a viable alternative for calculation of oscillating cascade aerodynamics. Buffum, Daniel H. and Fleeter, Sanford Glenn Research Center NASA-TM-103250, E-5677, NAS 1.15:103250 RTOP 535-05-01...

Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade with Supersonic Leading-Edge Locus
Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade with Supersonic Leading-Edge Locus

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-05-29

Total Pages: 64

ISBN-13: 9781720448167

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An experimental influence coefficient technique was used to obtain unsteady aerodynamic influence coefficients and, consequently, unsteady pressures for a cascade of symmetric airfoils oscillating in pitch about mid-chord. Stagger angles of 0 deg and 10 deg were investigated for a cascade with a gap-to-chord ratio of 0.417 operating at an axial Mach number of 1.9, resulting in a supersonic leading-edge locus. Reduced frequencies ranged from 0.056 to 0.2. The influence coefficients obtained determine the unsteady pressures for any interblade phase angle. The unsteady pressures were compared with those predicted by several algorithms for interblade phase angles of 0 deg and 180 deg.Ramsey, John K. and Erwin, DanGlenn Research CenterUNSTEADY AERODYNAMICS; INFLUENCE COEFFICIENT; PRESSURE MEASUREMENT; PRESSURE OSCILLATIONS; WIND TUNNEL TESTS; CASCADE FLOW; MACH NUMBER; SUPERSONIC FLUTTER; AIRFOIL OSCILLATIONS; PRESSURE DISTRIBUTION; SUPERSONIC WIND TUNNELS

Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade with Supersonic Leading-Edge Locus
Comparison of Theoretical and Experimental Unsteady Aerodynamics of Linear Oscillating Cascade with Supersonic Leading-Edge Locus

Author: Nasa Technical Reports Server (Ntrs)

Publisher: BiblioGov

Published: 2013-07

Total Pages: 68

ISBN-13: 9781289268114

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An experimental influence coefficient technique was used to obtain unsteady aerodynamic influence coefficients and, consequently, unsteady pressures for a cascade of symmetric airfoils oscillating in pitch about mid-chord. Stagger angles of 0 deg and 10 deg were investigated for a cascade with a gap-to-chord ratio of 0.417 operating at an axial Mach number of 1.9, resulting in a supersonic leading-edge locus. Reduced frequencies ranged from 0.056 to 0.2. The influence coefficients obtained determine the unsteady pressures for any interblade phase angle. The unsteady pressures were compared with those predicted by several algorithms for interblade phase angles of 0 deg and 180 deg.

Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines and Propellers
Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines and Propellers

Author: H.M. Atassi

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 876

ISBN-13: 1461393418

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The first International Symposium on Unsteady Aerodynamics and Aero elasticity of Turbomachines was held in Paris in 1976, and was followed by symposia at Lausanne in 1980, Cambridge in 1984, Aachen in 1987, Bei jing in 1989, and Notre Dame in 1991. The proceedings published following these symposia have become recognized both as basic reference texts in the subject area and as useful guides to progress in the field. It is hoped that this volume, which represents the proceedings of the Sixth International Symposium on Unsteady Aerodynamics of Turbomachines, will continue that tradition. Interest in the unsteady aerodynamics, aeroacoustics, and aeroelasticity of turbomachines has been growing rapidly since the Paris symposium. This expanded interest is reflected by a significant increase in the numbers of contributed papers and symposium participants. The timeliness of the topics has always been an essential objective of these symposia. Another important objective is to promote an international exchange between scien tists and engineers from universities, government agencies, and industry on the fascinating phenomena of unsteady turbomachine flows and how they affect the aeroelastic stability of the blading system and cause the radiation of unwanted noise. This exchange acts as a catalyst for the development of new analytical and numerical models along with carefully designed ex periments to help understand the behavior of such systems and to develop predictive tools for engineering applications.

An Experimental Study on the Aerodynamic Response of a Subsonic Cascade Oscillating Near Stall
An Experimental Study on the Aerodynamic Response of a Subsonic Cascade Oscillating Near Stall

Author: Franklin O. Carta

Publisher:

Published: 1976

Total Pages: 107

ISBN-13:

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Tests were performed on a linear cascade of airfoils oscillating in pitch about their midchords at frequencies up to 17 cps, at velocities up to 200 ft/sec and at interblade phase angles of 0 and 45 deg, under conditions of high aerodynamic loading. The measured data included unsteady time histories from chordwise pressure transducers and chordwise hot films. Unsteady normal force coefficient, moment coefficient, and aerodynamic work per cycle of oscillation were obtained from integrals of the pressure data, and indications of the nature and extent of the separation phenomenon were obtained from an analysis of the hot film response data. The most significant finding of this investigation is that a change in interblade phase angle from 0 deg to 45 deg radically alters the character of the blade loading (which governs its motion in a free system) from stable to unstable. Furthermore, the stability or instability is governed primarily by the phase angle of the pressure distribution over the forward 10 to 15 percent of the blade chord. Reduced frequency and mean incidence angle changes were found to have a relatively minor effect on stability for the range of parameters tested. (Author).

A Linear Aerodynamic Analysis for Unsteady Transonic Cascades
A Linear Aerodynamic Analysis for Unsteady Transonic Cascades

Author: Joseph M. Verdon

Publisher:

Published: 1984

Total Pages: 84

ISBN-13:

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A potential flow analysis to predict unsteady airloads produced by the vibrations of turbomachinery blades operating at transonic Mach numbers is presented. The unsteady aerodynamic model includes the effects of blade geometry, finite mean pressure variation across the blade row, high frequency blade motion, and shock motion within the framework of a linearized, frequency domain formulation. The unsteady equations are solved implicit, least squares, finite difference approximation which is applicable on arbitrary grids. A numerical solution for the entire unsteady field is determined by matching a solution determined on a rectilinear type cascade mesh, which covers an extended blade passage region, to a solution determined on a detailed polar type local mesh, which covers and extends well beyond the supersonic region(s) adjacent to a blade surface. Cascades of double circular arc and flat plate blades demonstrate the unsteady analysis, and partially illustrate the effects of blade geometry, inlet Mach number, blade vibration frequency and shock motion on unsteady response.

Aerodynamics of Cascaded Airfoils Oscillating Or Subject to Three-Dimensional Periodic Gusts
Aerodynamics of Cascaded Airfoils Oscillating Or Subject to Three-Dimensional Periodic Gusts

Author: H. Atassi

Publisher:

Published: 1980

Total Pages: 42

ISBN-13:

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Three problems which have been investigated are discussed in this report. Aerodynamic theory and computational procedures have been developed to study the aeroelastic stability of oscillating loaded airfoils in cascade with interblade phase angle. Contrary to linear theory, results show that classical flutter can occur for low speed turbine cascades operating at typical design conditions. Ground effects on fan inlet flows were investigated based on data from NASA - Lewis. The analysis showed that swirling flows are the dominant source of flow disturbances entering the fan. Finally, a study was made of three-dimensional periodic disturbances acting upon loaded airfoils in cascade. (Author).