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Analysis and reconstruction of dynamic-stall data from nominally two-dimensional aerofoil tests in two different wind tunnels

Gobbi, Giangiacomo (2010) Analysis and reconstruction of dynamic-stall data from nominally two-dimensional aerofoil tests in two different wind tunnels. PhD thesis, University of Glasgow.

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Abstract

This work is a specific investigation into low speed aerofoils. The term “low speed” is normally used to indicate free stream velocity less than Mach = 0.5 and, here, not more than 0.2 M when considering dynamic-stall. This field of investigation, for the QinetiQ aerofoil, has been somewhat ignored till now to the advantage of higher speeds starting from 0.3 M. In order to improve the knowledge of the behaviour of aerofoils under M<0.2 conditions, the University of Glasgow, in cooperation with QinetiQ, carried out two-dimensional aerodynamic tests on a RAE9645 aerofoil in 2002. By the end of November, of the same year, high quality unsteady pressure measurements from dynamic-stall tests were available. The tests were conducted on two different RAE9645 aerofoil models in two different wind tunnels. The first of these data came from the aerofoil that was tested in the Department of Aerospace’s Handley Page Wind Tunnel. The second data set was from tests carried out by QinetiQ on an aerofoil in the Department of Aerospace’s Argyll Wind Tunnel. The objectives of this investigation are divided in three main topics. First part considers the analysis of the data. This means (a) the assessment of the aerodynamic coefficients and consequent analysis of the various features of the dynamic-stall including the critical angle, the pitching moment and stall onset. (b) A comparison of the overall aerodynamic coefficients and (c) the carry out of final analysis of the most important quantities such as Cp deviation, vortex development and convection speed and re-establishment of fully attached flow. The assessment of the all same quantities for the second aerofoil tested by QinetiQ and the comparison of them xxiii with the first model are the objectives of the second part of the project. Hence a most useful comparison of two data sets from two different wind tunnels will be achieved. The third part was to establish the coefficients for the Beddoes third generation dynamic-stall model for the clean aerofoil without any flow control, using both aerofoil data. The Beddoes third generation dynamic-stall model is the last version of a model which has been in constant development over thirty years and is known as the most popular semi empirical method for assessing unsteady airloads such as lift, drag and pitching moment. This applies both to helicopters and wind turbines. The simplicity and undergoing philosophy of this method is its strength, especially compared with the current solution of Navier-Stokes or Euler equations. At the completion of this work, all the coefficients and information necessary for running the Beddoes simulating dynamicstall model were obtained for the RAE9645 aerofoil. At the same time refinements, improvements and new guide lines were pursued in order to make the model easier and more powerful than before. Some of these changes are associated only to low Mach numbers. It has been concluded that the Beddoes’ model has been enhanced to better re-construct the RAE9645 aerofoils data of low Mach numbers.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: unsteady aerodynamics, dynamic stall, onset of dynamic stall, reattachment process
Subjects: T Technology > TL Motor vehicles. Aeronautics. Astronautics
Colleges/Schools: College of Science and Engineering > School of Engineering > Aerospace Sciences
Supervisor's Name: Galbraith, Prof. R.A.
Date of Award: 2010
Embargo Date: 10 December 2015
Depositing User: mr giangiacomo gobbi
Unique ID: glathesis:2010-1362
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 Dec 2009
Last Modified: 04 Feb 2013 15:48
URI: http://theses.gla.ac.uk/id/eprint/1362

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