wake vortex encounter gust size and magnitude flight...

WVE Gust Size and Magnitude Flight Data

WakeNet, 3 EU, Toulouse, 28th/29th June, 2010

Wake Vortex Encounter Gust Size

and Magnitude Flight Data

A P BrownFlight Research Laboratory,

NRC Aerospace

presented toWakeNet3-Europe 2nd Major Workshop

Developments in wake Turbulence SafetyToulouse, 28th/29th June, 2010



Presentation

– Flight data (NRC program)

– Context of gust size/rise/fall-lengths and

magnitudes (gust peak speeds)

– Example of flight data

– Continuous turbulence

– Rise/fall analysis

– Discrete (turbulent trailing vortex cores)



CONTEXT – Proceeding to a definition of an acceptable WVE:

– Requires design & certification of structure, aeroservoelasticity, systems,

aerodynamics; in turn

– Requires definition of WVE gust magnitudes and rise-lengths, for

the formulation of design standards:-

– Discrete gusts, and

– Continuous gust spectra

– Combination (superposition)?

– Not presently required for aircraft gust-load certification



In which WVE realms:

– Both following realms are desirable:-

– Improvement upon existing landing-approach WT separation

standards, and

– Establishment of enroute WT separation standards

– both involve tWAKE O[40:120] seconds

– wake vortex trailing pair probably have turbulent cores,

may be in significant individual or/and mutual

instability state

– flight data has both dissipative turbulence scale

and intensifying turbulent scales, which are more

likely to be core instability modes



EXAMPLE – Trailing pair crossplane-

referenced vortex-induced wind perturbations

-60 -40 -20 0 20 40 60

-400

-300

-200

-100

0

100

0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0 4 0 0 0 4 5 0 0- 3 0

- 2 0

- 1 0

0

1 0

2 0

3 0

d s o - s u m , b a s e d u p o n T A S & ψ

wc wa wZ

wc

wa

wZ

0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0 4 0 0 0 4 5 0 00

5

1 0

1 5

2 0

2 5

3 0

d s o - s u m , b a s e d u p o n T A S & ψ



Trailing pair crossplane

Continuous gust spectra

10-2

10-1

100

101

10-5

10-4

10-3

10-2

10-1

100

101

102

103

PSD of longitudinal gus tines s , vortex core travers es

s patial frequency (rad/ft)

continuous gust PSD (ft/s)2/(rad/ft))

flight data ,8-15 nm wake length, 53-90 s ec age

FAR25,App.F with Uσ=85 fps with σ=85/3.5 fps




– FAR 25 for typical weight/dim 50-

70,000 lb transport a/c

10-2

10-1

100

101

10-5

10-4

10-3

10-2

10-1

100

101

102

PSD of lateral gus tines s , vortex core travers es



flight data,8-15 nm wake length, 53-90 s ec age





10-2

10-1

100

101

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

PSD of vertical gus tines s , vortex core travers es



flight data ,8-15 nm wake length, 53-90 s ec age




Rise and fall magnitudes & lengths

(peaks and troughs counting) of wCZ

1.08 1.085 1.09 1.095 1.1 1.105 1.11 1.115 1.12

x 105

0

5

10

15

20

25

0 5 10 15 20 25 30 350

2

4

6

8

10

12

14

16

18

gust-rise magnitude (m/s)

gus t-ris e length (m)

A380

Ris ing gus t

Falling gus t

Typ M FAR 12.5c/66fps ris e-rate



0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40

0.5

1

1.5

2

2.5

normalised gust-rise magnitude, VT/(

Γ/bV)

normalis ed gus t-ris e length, s /bGEN

A380

Rise and fall magnitudes & lengths

of wCZ normalised

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40

0.5

1

1.5

2

2.5

normalised gust-rise magnitude, VT/(

Γ/bV)

normalis ed gus t-ris e length, s /bGEN

A380



WVE - discrete vortex core

traverses:

Modelling of gust-rise/fall shape

– depends upon extent of

asymptotic VT rise

– examine flight data traverses

-25 -20 -15 -10 -5 0 5 10 15 20 25-30

-20

-10

0

10

20

30

dis tance (m)

VT ()m/s

1-cos

Burnham-Hallock

line vortex

s kewed 1-cos



Vortex core traverses:

ΓGEN ≈≈≈≈ 735 m2/s

– Wake age, t = 53 sec

– Wake length 7.5 nm, Γ = 630 m2/s

– advance/recede tails overlay

– Superposition of mean + turbulent,

peak VT > 20 m/s (66 fps)

WVE Gust Magnitudes/Rise-lengths

0 5 10 15 20 25 30 350

5

10

15

20

25

30

rC m1/1

wCZ m/s

advance to vortex centre

recede from centre

5-15m B-H, Γ=682.9464 rC=3.7094

Rankine, Γ=628.5 rC=3.5

0.8 1 1.2 1.4 1.6 1.8 2-5

0

5

10

15

20

25

30

rC m1/5

wCZ m/s


poly fit

recede from centre

5-15m B-H, Γ=682.9464 rC=3.7094




0 5 10 15 20 250

5

10

15

20

25

30

r m1/1

wCZ m/s


recede from centre

5-15m B-H, Γ=626.9098 rC=5.9714



Rankine, Γ=395.955 rC=2.9316

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 20

5

10

15

20

25

30

r m1/5

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=626.9098 rC=5.9714



Rankine, Γ=395.955 rC=2.9316

Vortex core traverse #2:


– Wake length 8 nm

– Γ = O[630] m2/s

– Sec features away from core edges



0 5 10 150

5

10

15

20

25

30

35

40

r m1/1

wCZ m/s


recede from centre

5-15m B-H, Γ=626.5063 rC=2.1544



1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.80

5

10

15

20

25

30

35

40

r m1/5

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=626.5063 rC=2.1544





– Wake length 8.4 nm

– Γ = O[620] m2/s

– Lower turbulence, B-H models well






– Γ = O[600] m2/s

– large VT’ near core edge

0 5 10 150

5

10

15

20

25

30

r m1/1

wCZ m/s


recede from centre

B-H, for Γ=628.5 rC=4.5


1.1 1.2 1.3 1.4 1.5 1.6 1.70

5

10

15

20

25

30

r m1/5

wCZ m/s


recede from centre

B-H, for Γ=628.5 rC=4.5




0 1 2 3 4 5 6 7 8 90

5

10

15

20

25

30

r m1/1

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=260.9275 rC=1.3153

Rankine, Γ=62.8945 rC=0.37074

0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.60

5

10

15

20

25

30

r m1/5

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=260.9275 rC=1.3153

Rankine, Γ=62.8945 rC=0.37074




– Γ = O[580] m2/s

– Secondary vortex, VT~r1/5 profile



0 0.5 1 1.5 2 2.5 30

5

10

15

20

25

r m1/1

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=64.3682 rC=0.5

Rankine, Γ=76.2643 rC=0.52773

0.8 0.85 0.9 0.95 1 1.05 1.1 1.15 1.2 1.250

5

10

15

20

25

r m1/5

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=64.3682 rC=0.5

Rankine, Γ=76.2643 rC=0.52773




– Γ = O[570] m2/s

– Secondary vortex



Vortex core traverse No.7:


– Wake length, 12.6 nm

– Γ = O[380] m2/s

0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.60

2

4

6

8

10

12

14

16

18

20

rC m1/5

wCZ m/s


poly fit

recede from centre

5-15m B-H, Γ=309.6268 rC=2.3681


0 5 10 15 20 250

2

4

6

8

10

12

14

16

18

20

r m1/1

wCZ m/s


recede from centre

5-15m B-H, Γ=309.6268 rC=2.3681




1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1

2

4

6

8

10

12

14

16

r m1/5

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=368.4531 rC=6

Rankine, Γ=368.4531 rC=6

0 5 10 15 20 25 30 35 40 45 500

2

4

6

8

10

12

14

16

18

r m1/1

wCZ m/s


recede from centre

poly fit

5-15m B-H, Γ=368.4531 rC=6

Rankine, Γ=368.4531 rC=6

Vortex core traverse No.8:


– Wake length, 14.2 nm

– Γ = O[360] m2/s



– Have considered WVE gust size & magnitude 8-20nm wake survey flight data,

from the viewpoints of

– Continuous turbulence spectra loading, for helices around & through vortices

– Ώ(vZ) of the order of magnitude of FAR 25 design limit spectra; and

– Rise/fall peaks & troughs analysis (typ. For fatigue loading)

– groupings of gust rise/falls into a number of discrete non-dim rates

– Possibility of normalising by generator

– discrete vortex core traverse size/magnitude profiles

– Examined eight profiles in detail:- for each , mean + turbulent (VT’/VTO[50-100%) flow superposition evident; peak VT > 66 fps, FAR limit mag.

– Line vortex (Rankine) model, &

– Burnham-Hallock model – generally (7/8 times) under-estimated VT at

core edges – for the good ID, core traverse had low turbulence content;

– Line vortex model captured core edge VT augmentation by sec

vortices, implying non-dissipative in nature, core-stability driven?

– Further examination of existing & future data warranted.

Conclusions:– WVE, present & future occur with trailing

vortices likely turbulent, incl. cores



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