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|Document Type: ||Thesis or dissertation|
|Title: ||A Parametric Study of Vane and Air-jet Vortex Generators|
|Authors: ||Bray, Tim P.|
|Supervisors: ||Garry, Kevin P.|
|Issue Date: ||Oct-1998|
|Abstract: ||An experimental parametric sturdy of vane and air-jet vortex generators in a turbulent boundary
layer has been carried out. Experiments were carried out in two facilities, one with a free-stream
velocity of 20 m/s and a boundary layer thickness (6) of 41.5 mm, and one in a high speed facility
at free-stream Mach numbers of between 0.45 and 0.75 and a boundary layer thickness of 20 mm.
Cross-stream data were measured at a number of downstream locations using a miniature five-hole
pressure probe, such that local cross-stream velocity vectors could be derived. Streamwise
vorticity was calculated using the velocity vector data.
In the low speed study, vortex generator parameters were as follows:
" Vane vortex generators: thin rectangular vanes with a vane aspect ratio of unity (2h/c = 1),
free-stream velocity 20 m/s, incidence (cc = 10', 15', 18', 20'), height-to-boundary- layer-
thickness-ratio (h/8 0.554,0.916,1.27,1.639), and strearnwise distance from the vortex
generator (x/6 = 3.855,12.048,19.277,26.506).
" Air-jet vortex generators: circular jet nozzles, free-stream velocity = 20 m/s, jet nozzle pitch
and skew angles (cc, P= 30', 45', 60'), hole diameter-to-boundary-layer-thickness-ratio (D/5 =
0.098,0.193,0.289), jet-to-free-stream-velocity ratio (VR = 0.7,1.0,1.3,1.6,2.0), and
strearnwise distance from the vortex generator (x/8 = 3.855,12.048,19.277,26.506).
In the high-speed study, the vortex generator parameters were as follows:
Vane vortex generators: thin rectangular vanes with an aspect ratio of unity, incidence ((X
1505 20'), he i ght-to- boundary- I ayer-th i ckne s s-rati o (h/8 = 0.75), strearnwise distance from the
vortex generator (x/6 = 8.755 16.25,23.75), and free-stream Mach numbers of 0.45,0.6 and
Air-jet vortex generators: jet pitch ((x = 30', 45'), jet skew angle (P = 30', 45', 60'), hole
diameter-to-boundary-layer-thickness-ratio (D/8 = 0.15,0.3), j et-to- free- strearn-ve loc ity ratio
(VR = 1.6), and strearnwise distance from the vortex generator (x/6 = 8.75,16.25,23.75,
31.25), and free-stream Mach numbers of 0.50,0.6 and 0.75.
Streamwise vorticity data from the experiment was used to generate prediction techniques that
would allow the vorticity profiles, downstream of vane or air-jet vortex generators, to be predicted.
Both techniques are based on the approximation of the experimental cross-stream vorticity data to
Gaussian distributions of vorticity through the vortex centre. The techniques, which are
empirically derived, are simple equations that give the peak vorticity and vortex radius based on
the vortex generator parameters. Use of these descriptors allows the assembly of the Gaussian
Both techniques are compared with the experimental data set and were seen to produce peak
vorticity results to within 12% and 20% (for the vanes and air-jets respectively), 15% for the
radius of the vortex, and 15% and 20% in vortex circulation (for the vanes and air-jets
respectively). The two simple prediction techniques allow good prediction of the vortex structure
at extremely low computational effort.|
|Appears in Collections:||PhD and Masters by research theses (School of Engineering)|
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