Contract Report for The Science And Engineering Research Council. Contract Number Gr/F/06760. G.U. Aero Report 9201

This document constitutes the final report for SERC award No. GR/F/06760. It first details the work programme of the original proposal made in 1987 and notes the work done to illustrate completion and extensions beyond that proposed. For brevity, we confine the technical discussion to the salient features of a particular aerofoil, albeit the work was an integral part of a larger programme on dynamic stall. The extent of this work may be gleaned from the accompanying enclosures representing some recent activity at Glasgow University. Two of the main technical results from the present authors are worthy of note in that the first (i.e. a correletion for incipient dynamic stall) has been used both in industry (VAWT Ltd) and research (under SERC GR/F/63466) to propose new aerofoil shapes for wind turbines. The second, however, (negative lift at large incidence during ramp-down motions from the stalled condition) has generated a new research activity (funded under SERC GR/H167U). This and future prospects are discussed prior to the concluding remarks. These remarks express the authors opinion of the success and overall value of the programme

An Examination of Dynamic Stall Vortex Inception on a Finite Wmg

In the present study, the behaviour of the vorticity flux on a wing of NACA 0015 cross section was analysed for ramp-up motion over a range of dimensionless pitch rates. The variations in the vorticity flux were examined as a means to identify the role of the vorticity leaving the boundary layer in the initiation, development and growth of the dynamic stall vortex. It has been found that there are two main sources of bipolar vorticity located within the first 3% of the chord at all span wise stations on the wing. These sources move and change strength as the wing is pitched through the incidence range. One factor that influences their behaviour is the reduced pitch rate and this effect is discussed. Further, it is shown that there is an apparent link between the negative source of vorticity and the first observable manifestation of the dynamic stall vortex on the pressure distribution near the mid-span

Control of rotorcraft retreating blade stall using air-jet vortex generators

A series of low-speed wind tunnel tests were carried out on an oscillating airfoil fitted with two rows of air-jet vortex generators (AJVGs). The airfoil used had an RAE 9645 section and the two spanwise arrays of AJVGs were located at x/c=0.12 and 0.62. The devices and their distribution were chosen to assess their ability to modify/control dynamic stall; the goal being to enhance the aerodynamic performance of helicopter rotors on the retreating blade side of the disc. The model was pitched about the quarter chord with a reduced frequency (k) of 0.1 in a sinusoidal motion defined by a=15o+10sin_ t. The measured data indicate that, for continuous blowing from the front row of AJVGs with a momentum blowing coefficient (C μ) greater than 0.008, modifications to the stalling process are encouraging. In particular, the pitching moment behavior exhibits delayed stall and there is a marked reduction in the normal force hysteresis

Collected Data for Tests on NACA 0015 Aerofoil with Chord of Length 0.275m. G.U. Aero Report 9209

Herein is presented the collected data for tests in which a NACA 0015 aerofoil with chord of length 0.275m, was subjected to a variety of displacements in pitch about the quarter-chord location at low Reynolds numbers

Collected Data for Tests on NACA 0015 Aerofoil with Chord of Length 0.275m. G.U. Aero Report 9209

Herein is presented the collected data for tests in which a NACA 0015 aerofoil with chord of length 0.275m, was subjected to a variety of displacements in pitch about the quarter-chord location at low Reynolds numbers