Validation of Wake Vortex Encounter Simulation Models

Using Flight Test Data

Dietrich FischenbergDLR Institute of Flight Systems

Braunschweig

WorkshopWakeNet2-Europe, Working Group 5, Hamburg, 10 -11 May 2004

Assessment ofWake Vortex

Safety

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Scope of Presentation

flight tests, measurements, and data

flight test data analysis performed within the S-WAKE project:

• determination of vortex model parameters to characterize vortex flow field

• validation of flight mechanic/aerodynamic interaction models

summary

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Statistics of Full Scale Flight Encounter

Date EncounterA/C

Altitude Encounterflown

Flap setting ofwakegenerating A/C

DLC-flapsetting

14.8.2001 Dornier Do128 FL 95 24 14° const.

15.8.2001 Dornier Do128 FL 95 27 14°, 35° const.

21.8.2001 Dornier Do128 FL 95 15 14°, 1° split,oscillating

15.3.2002 CessnaCitation

FL 150 25 14° const.

22.3.2002 Dornier Do128 FL 100 25 14°, 35° const.

total 116

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Wake Generating Aircraft ATTAS

ATTAS with extended flaps smoke generator in action

smoke trace,oscillating DLC flaps

smoke trace,constant DLC flaps

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Encounter Aircraft

Dornier Do 128 (TU-BS)4 flow probes (5 hole probes)

4,2

m 2,3

mCessna Citation II (NLR)

1 flow probe (vanes)

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Encounter Maneuver

smoke trace

0.5 nmwake

generation1.5 nm

3.0 nm

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Flight Test Encounter Scenario

smoke trace

0.5 nmwake

generation1.5 nm

3.0 nm

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Do128 Typical Encounter Flow Sensor Measurements

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The 2 Steps of Encounter Flight Test Data Evaluation

basicA/C aero

model

basicA/C aero

model

aerodynamic interaction

model

aerodynamic interaction

model

pilot’scontrolinputs

forces,moments

∆ forces, ∆ moments

+

+

6-DOFA/C

simulation

6-DOFA/C

simulation

+

-outputs

accelerations, rates, attitude, altitude, velocity

modelaccuracy

step 2

measuredflight test

data

measuredflight test

data

flow measurements

flightpath

reconstruction(FPR)

flightpath

reconstruction(FPR)

accelerations,rates,

attitude,altitude,velocity

Vortex model

step 2:“encounter model validation“

wake vortexcharacteristicsstep 1

step 1:“flow field characterization“

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Validation Basic Do128 Model - no Wake Vortex Influence

________ measured________ model output

lateralaccel.

verticalaccel.

rollrate

pitchrate

0 20 time, s-10

30-40

40-25

0-4

6

DEG/S

DEG/S

M/S2

M/S 2

1 5432

yawrate

bankangle

pitchangle

yawangle

0 20 time, s100

500-10

10-100

100-40

40DEG/S

DEGDEG

DEG

DEG

1 5432

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Determination of Vortex Model Parameters: Rosenhead - B & H

horizontal velocity vertical velocity

measuredmodeloutput

noseboomsensor

rightwing

sensor

leftwing

sensor

verticaltail

sensor

-15

10

20 15

10

20

-15 -10

10 10

-5 -15

-15

-10

15

-5

m/s

m/s

m/s m/s

m/s

m/s

m/s m/s

time, s time, s10 2 4 63 5 10 2 4 63 5

distance: 0.8 nm

Identified:Γ = 115.3 m2/s

rC = 0.90 m(=4.2% wing span)

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Determination of Vortex Model Parameters: Winckelmans

horizontal velocity vertical velocity

measuredmodeloutput

noseboomsensor

rightwing

sensor

leftwing

sensor

10

-10 -30

20 20

-30 -20

10

m/s

m/s m/s

m/s

m/s m/s

time, s time, s10 2 4 63 5 10 2 4 63 5

-15 -10

20 10

hit of vortex core

distance: 0.6 nm

Identified:Γ = 152 m2/s

rC = 0.22 m(=1% wing span)

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Do128: Comparison of Different Vortex Models

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Aerodynamic Interaction Models

Strip Method (SM)ONERA

Lifting Surface Method (LSM)TU Berlin

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Validation of Strip Method (SM):Simulation of ATTAS/Do128 Wake Vortex Encounters

yawrate

bankangle

pitchangle

yawangle

140

200-5

10-40

40-12

12DEG/S

DEG

DEG

DEG

0 20 time, s

lateralaccel.

verticalaccel.

rollrate

pitchrate

-15

10-50

50-20

0-3

3

DEG/S

DEG/S

M/S 2

M/S2

0 20 time, s

Encounter 1:right left

Encounter 2:left right

Encounter 1:right left

Encounter 2:left right

________ measured________ simulation model output

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Validation of Lifting Surface Method (LSM):Simulation of ATTAS/Do128 Wake Vortex Encounter

Encounter 1:right left

Encounter 2:left right

Encounter 1:right left

Encounter 2:left right

yawrate

bankangle

pitchangle

yawangle

140

200-5

10-40

40-12

12DEG/S

DEG

DEG

DEG

0 20 time, s

lateralaccel.

verticalaccel.

rollrate

pitchrate

-15

10-50

50-20

0-3

3

DEG/S

DEG/S

M/S 2

M/S2

0 20 time, s

________ measured________ simulation model output

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Summary

S-WAKE flight test measurements (116 encounter) are a valuable high quality data base

Flight test data were successfully evaluated with parameter identification and flight path reconstruction techniques to determine parameters of wake vortex models (Rosenhead & Burnham-Hallock, Lamb-Oseen, Winckelmans)

Flight test data were successfully evaluated to validate aerodynamic interaction models (AIMs) for near parallel encounter cases (strip method, lifting surface method)

In general, both AIMs are suitable to simulate wake vortex encounters (especially roll and vertical axes). Overall, both methods show equally good results.