flexible flaps for separation control on a wing with low aspect ratio
DESCRIPTION
Flexible flaps for separation control on a wing with low aspect ratio. Dipl. Ing. G. Patone Dr. W. Müller Dr. R. Bannasch Prof. Dr. Ing. I. Rechenberg. bionics pilot project:. Aeroflexible surface flaps as "eddy-breaks" built after the covert feathers of birds. Project partners: - PowerPoint PPT PresentationTRANSCRIPT
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Flexible flaps for separation control on a wing with low
aspect ratio
Dipl. Ing. G. Patone
Dr. W. MüllerDr. R. Bannasch
Prof. Dr. Ing. I. Rechenberg
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bionics pilot project:
Aeroflexible surface flaps as "eddy-breaks"
built after the covert feathers of birds
Project partners:• DLR Abt. Turbulenzforschung • Firma Stemme GmbH• Fachgebiet Bionik und Evolutionstechnik an der
TU-Berlin
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main objective:
eddy
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Brown Skua with “eddy-flaps”
lifted covert feathers 0
1
2
3 eddy- flaps
eddy
5
0
1
2
3
aerofoil with eddy- flaps
eddy- flaps
6
cL
goal:
not like this but like this
cL
cL cL
cD
cD
7
research goal
• improving the stall behavior of an aerofoil
• flaps should not have any negative effects while not active
• flaps should work without external controls
8
experimental setup at the wind tunnel
lift-balance
wind tunnel10m/s
drag-balance pressure sensor and scanivalve
NACA 2412 aerofoil with an aspect ratio of 3.5
Re= 130.000
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porosity
px
pypxpypy
px
py
-
+
px
pypy
a
b c
schematic pressure distribution
px > py
impervious materials are lifted off by the pressure differences
porous materials remainon the surface
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200mm
700m
m
100a
aerofoil with silk flaps
silk
steel wire
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silk flaps
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 10 20 30 40
CL
without flaps
with silk flaps ( a=15%t; b=50%t)
NACA 2412
t
ba
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polar diagram for ‘perforated plastic sheet’ flaps
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 10 20 30 40
CL
`perforated plastic sheet` flaps(a=15%t, b=35%t)fixed `perforated plastic sheet` flaps
NACA 2412
t
ba
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aerofoil for pressure distribution
7
6
54321
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pressure distribution at 16 degrees
incident airflow
without flaps
with flaps
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pressure distribution at 19 degrees
incident airflow
without flaps
with flaps
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flow visualisation
stationärer Wirbel instationäre Strömungsverhältnisse
v
trapped vortex trapped eddy
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pressure distribution at 36 degrees
incident airflow
without flaps
with flaps
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polar diagram (calculated from all measuring rows)
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 10 20 30 40
CL
without flap with flap
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lift distribution without flaps at different angles of attack
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 100 200 300 400 500 600 700mm
CL
18°
19°
36°
1°
24°
6°
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lift distribution with flaps at different angles of attack
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 100 200 300 400 500 600 700mm
CL
18°
19°36°
1°
24°
6°
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summary:
• eddy flaps prevent sudden drop in lift generation during stall
• pressure distribution indicates: eddy-flaps restrict eddy to hind part of aerofoil
outlook:
• automatic contour adapting flaps• dynamic stall behaviour