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

TL Motor vehicles. Aeronautics. Astronautics

Gobbi, Giangiacomo ; Galbraith, R.A.

University:University of Glasgow

Department:School of Engineering

关键词: unsteady aerodynamics, dynamic stall, onset of dynamic stall,reattachment process.;   

Others  :  http://theses.gla.ac.uk/1362/1/2009GobbiPhD.pdf

来源: University of Glasgow

【 摘 要 】

This work is a specific investigation into low speed aerofoils. The term “low speed” isnormally used to indicate free stream velocity less than Mach = 0.5 and, here, not morethan 0.2 M when considering dynamic-stall. This field of investigation, for the QinetiQaerofoil, has been somewhat ignored till now to the advantage of higher speeds startingfrom 0.3 M. In order to improve the knowledge of the behaviour of aerofoils underM<0.2 conditions, the University of Glasgow, in cooperation with QinetiQ, carried outtwo-dimensional aerodynamic tests on a RAE9645 aerofoil in 2002. By the end ofNovember, of the same year, high quality unsteady pressure measurements fromdynamic-stall tests were available. The tests were conducted on two different RAE9645aerofoil models in two different wind tunnels. The first of these data came from theaerofoil 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 theDepartment of Aerospace’s Argyll Wind Tunnel. The objectives of this investigation aredivided 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 variousfeatures of the dynamic-stall including the critical angle, the pitching moment and stallonset. (b) A comparison of the overall aerodynamic coefficients and (c) the carry out offinal analysis of the most important quantities such as Cp deviation, vortex developmentand convection speed and re-establishment of fully attached flow. The assessment of theall same quantities for the second aerofoil tested by QinetiQ and the comparison of themxxiiiwith the first model are the objectives of the second part of the project. Hence a mostuseful 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 generationdynamic-stall model for the clean aerofoil without any flow control, using both aerofoildata. The Beddoes third generation dynamic-stall model is the last version of a modelwhich has been in constant development over thirty years and is known as the mostpopular semi empirical method for assessing unsteady airloads such as lift, drag andpitching moment. This applies both to helicopters and wind turbines. The simplicity andundergoing philosophy of this method is its strength, especially compared with thecurrent solution of Navier-Stokes or Euler equations. At the completion of this work, allthe coefficients and information necessary for running the Beddoes simulating dynamicstallmodel 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 andmore powerful than before. Some of these changes are associated only to low Machnumbers.It has been concluded that the Beddoes’ model has been enhanced to better re-constructthe RAE9645 aerofoils data of low Mach numbers.