Author: Steven Dale Hedrick
Publisher:
ISBN:
Category :
Languages : en
Pages : 73
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Book Description
The primary goal of this thesis was the development of an experimental technique, and supporting software, for the acquisition and analysis of unsteady velocity data generated by an oscillating airfoil. This research was in support of a major investigation of the compressibility effects on dynamic stall. The experimental procedure involved schlieren flow visualization for comparison of steady and unsteady flow fields, and for determination of parameters for further study. Laser Doppler velocimetry was employed for obtaining velocity data in the airfoil wake. For unsteady data, the airfoil was oscillated in pitch about its quarter chord. The data analysis produced wake profile plots representing the flow field distributed by the airfoil. Results were obtained for steady and unsteady conditions. Keywords: Laser doppler velocimetry, Schlieren flow visualization, Dynamic stall.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 165
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Book Description
Detailed measurements of an unsteady flow field within the inlet guide vanes (IGV) and the rotor of a radial inflow turbine were performed using a three component Laser Doppler Velocimeter (LDV) system together with a rotary encoder. The mean velocity, the flow angle and the turbulence contours for IGV passages are presented at four blade-to-blade planes for different rotor positions to give three dimensional, unsteady behavior of the IGV flow field. These results are compared with the measurements obtained in the same passage in the absence of the rotor. The flow field of the IGV passage was found to be affected by the presence of the rotor. The ratio of the tangential normal stresses to the radial normal stresses at the exit of the IGV was found to be more than doubled when compared to the case without the rotor. The rotor flow field measurements are presented as relative mean velocity and turbulence stress contours at various cross section planes throughout the rotor. The cross flow and turbulence stress levels were found to be influenced by the incidence angle. Transportation of the high turbulence fluid by the cross flow was observed downstream in the rotor blade passages. Radial Turbine Aerodynamics, LDV unsteady Flow Measurements.
Author: Ricky E. Wilson
Publisher:
ISBN:
Category :
Languages : en
Pages : 52
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Book Description
A computer-integrated LDV system utilizing a Helium-Neon laser was designed, assembled and tested for use in the study of steady flow field quantities. All system elements were integrated to include a traverse mechanism, signal processing and conditioning, computer interface and display. The system was initially calibrated utilizing a rotating wheel of known velocity. Experimental flow measurement tests of the system were conducted across a conventional free jet flow and in the Naval Postgraduate School low speed wind tunnel. The flow field velocity measurements made in the wind tunnel were verified usin an existing pressure data acquisition station and a standard pitot static probe. Keywords: Laser doppler velocimetry.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 38
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Book Description
Author: H.M. Atassi
Publisher: Springer Science & Business Media
ISBN: 1461393418
Category : Science
Languages : en
Pages : 876
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Book Description
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.
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781723515354
Category :
Languages : en
Pages : 386
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Book Description
Measurements were made in a large scale single stage turbine facility. Within the nozzle passage measurements were made using a five hole probe, a two-component Laser Doppler Velocimeter (LDV), and a single sensor hot wire probe. These measurements showed weak secondary flows at midchord, and two secondary flow loss cores at the nozzle exit. The casing vortex loss core was the larger of the two. At the exit radial inward flow was found over the entire passage, and was more pronounced in the wake. Nozzle wake decay was found to be more rapid than for an isolated vane row due to the rotor's presence. The midspan rotor flow field was measured using a two-component LDV. Measurements were made from upstream of the rotor to a chord behind the rotor. The distortion of the nozzle wake as it passed through the rotor blade row was determined. The unsteadiness in the rotor flow field was determined. The decay of the rotor wake was also characterized. Zaccaria, M. and Lakshminarayana, B. Glenn Research Center NASA-CR-4778, NAS 1.26:4778, E-10771 NAG3-555; RTOP 523-26-33...
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Book Description
Two component, phase averaged mean velocity data have been obtained with an LDV system, on the upper surface, near the leading edge of an oscillating airfoil undergoing compressible dynamic stall. In particular, the effect of oscillation amplitude has been studied. The results show that at an oscillation amplitude of 10 degrees, a separation bubble forms, that eventually bursts on the upstroke, well beyond the static stall angle. At 2 degrees amplitude, the bubble forms on the upstroke, but dynamic stall occurs on the downstroke. The results reveal new flow physics and the data sets serve as valuable quantitative information for validation of unsteady flow codes at transitional Reynolds numbers. The maximum velocity seen in the flow is about 1. 6 times the free stream value and it occurs slightly downstream of the suction peak location. Some the measurement difficulties are also discussed. Dynamic stall, Vorticity field, LDV Measurements, Compressibility effects.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 456
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author: M. Zaccaria
Publisher:
ISBN:
Category : Turbines
Languages : en
Pages : 394
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Book Description
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721004683
Category :
Languages : en
Pages : 36
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Book Description
Results are presented of an experiment conducted to investigate possible sources of fan noise in the flow developed by a 22-in. (55.9 cm) diameter turbofan model. Flow diagnostic data were acquired to identify possible sources of both tone and broadband noise. Laser Doppler velocimetry was used to characterize the tip flows that develop within the rotor blade passages, the wake flow downstream of the rotor, and the shock waves that develop on the blades when operated at transonic relative tip speeds. Single-point hot-wire measurements were made in the rotor wake to determine the frequency content and the length scales of the flow unsteadiness. The results document the changes in the rotor wake flow with both rotor speed and axial distance downstream of the rotor. The data also show the tip flow development within the blade passage, its migration downstream, and (at high rotor speeds) its merging with the blade wake of the following blade. Data also depict the variation of the tip flow with tip clearance. LDV data obtained within the blade passages at high rotor speeds illustrate the passage-to-passage variation of the mean shock position. Spectra computed from the single-point hot-wire measurements illustrate how the energy in the flow oscillations is split between periodic and random components, and how this split varies with both radial and axial position in the rotor wake.Podboy, Gary G. and Krupar, Martin J. and Helland, Stephen M. and Hughes, Christopher E.Glenn Research CenterSTEADY FLOW; UNSTEADY FLOW; FLOW DISTRIBUTION; TURBOFANS; MODELS; AERODYNAMIC NOISE; WAKES; ROTOR SPEED; LASER DOPPLER VELOCIMETERS; VELOCITY MEASUREMENT; FAN BLADES; BLADE TIPS; TIP SPEED; SHOCK WAVES; TRANSONIC SPEED; OSCILLATIONS
