1. Songhua Wu, Xiaochun Zhai, Bingyi Liu, Hongwei Zhang, Qichao Wang
19th Coherent Laser Radar Conference, June, Okinawa, Japan
Characterization of aircraft dynamic wake vortices and atmospheric turbulence by Coherent Doppler Lidar
Songhua Wu, Xiaochun Zhai, Bingyi Liu, Hongwei Zhang, Qichao Wang
Ocean University of China (OUC), Qingdao Qingdao National Laboratory for Marine Science and Technology, China
June 21, 2018

2. 19th Coherent Laser Radar Conference, Okinawa, June 18-21 2018
Outline
Motivation Wake vortex and its impact on aviation safety and efficiency
Methodology Coherent Doppler wind lidar Retrieval algorithm and data processing flow for dynamic wake vortex analysis
Field campaigns campaigns at the Beijing Capital International Airport (BCIA)
Summary

3. Wake vortex’s impact on aviation safety and efficiency
19th Coherent Laser Radar Conference, Okinawa, June
Wake vortex’s impact on aviation safety and efficiency
Occurrence of Wake Vortex Encounters
Severity of Wake Vortex Encounters
Aircraft safety
Airport capacity
Frederic Barbaresco et al, 2013
WV are large rolling air masses generated by aircraft because of lift. Core velocities of the vortex can exceed 60 m/s for large aircraft, constituting a potential hazard to following aircraft during the landing and take-off phases.
Existing departure and arrival wake turbulence separations are sometimes considered over conservative as they don’t take into account meteorological conditions likely to shift, reduce or alleviate the wakes’ circulations.
Most severe wake-vortex encounters mainly occur under 500 feet. The impact of a wake vortex encounter at low altitude is indeed more severe..

4. The signification of Near Ground Effect (NGE)
19th Coherent Laser Radar Conference, Okinawa, June
The signification of Near Ground Effect (NGE)
Puel and Victor, 2000.
Stephan, Misaka & Holzäpfel, 2012
The heights range of NGE and IGE are our most concerned area. The dynamics of wake vortex in this area is quite complicated.
Wake vortices leads to the formation of a shear layer at the ground, which eventually rolled up to secondary vortex structures and separated from the ground

5. Methodology: pulsed coherent Doppler wind lidar
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: pulsed coherent Doppler wind lidar
The position, characterization, evolution and decay of aircraft wake vortex can be derived from Doppler lidar measurements.
Doppler Spectrum

6. Methodology: Lidar Scanning modes
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: Lidar Scanning modes
Basic RHI mode Range-Height-Indicator Scan height at far distance: 500 m Elevation angle: 2°-30° Angle interval: 2°
Mar , BCIA
Velocity Spectrum y z x

7. Methodology: Scanning modes
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: Scanning modes
Basic RHI mode Range-Height-Indicator Scan height at far distance: 500 m Elevation angle: 2°-30° Angle interval: 2°
LOS velocity
velocity dispersion
ATOM mode Along Track Observation Mode with multiple elevation angle 2°, 6°, 10° etc. LOS Angle interval: 2° 4° y z x

8. Dynamic Wake Vortex detection
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: Diagram of real-time dynamic WV detection
Dynamic Wake Vortex detection
Lidar Observation
Wake Vortex Detection Core location Circulation TEDR
Wind
Profile & Turbulence
LES Model
Wake Simulation Core location Circulation

9. Radial velocity & spectrum width core position & circulation
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: wake vortex characteristics retrieval
Doppler
spectrum
Radial velocity & spectrum width
core position & circulation
Wind profile & TEDR
(b1)
(a)
Doppler
spectrum
(b2)
(b3)
Circulation is calculated by summation along an arc passing through the core center and between the radii 5 m and 15 m.
(a) Doppler spectrum measured at different elevation angles and at the fixed range equal to the distance between the Lidar and the right wake vortex, (b) spectrum of [b1] outside, [b2] below and [b3] above the right vortex core.

10. Radial velocity & spectral width core position & circulation
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: wake vortex characteristics retrieval
Doppler
spectrum
Radial velocity & spectral width
core position & circulation
Wind profile & TEDR
(a) Radial velocity
(b) Spectral width
CDL observed (a) radial velocity and (b) spectral width distribution when an A380 overflights on 14:47:16-10:49:58 LST Jan at BCIA.

11. Methodology: wake vortex characteristics retrieval
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: wake vortex characteristics retrieval
Doppler
spectrum
Radial velocity & spectral width
core position & circulation
Wind profile & TEDR
The distribution of function (a) Dv (Rk ; n) (green curve), Ds (Rk ; n) (blue curve)
(b) D (Rk ; n) (black curve), the red and blue line in the below figure represent the distribution of φ max ( R k ;n), and φ min R k ;n , respectively.
(c) the red and black square represent the left and right wake vortex, respectively.
(a)
(b)
(c)
Weighted function: D 𝑹 𝒌 ;𝒏 = 𝑫 𝒗 𝑹 𝒌 ;𝒏 * 𝑫 𝒔 𝑹 𝒌 ;𝒏 /𝟏𝟎

12. Radial velocity & spectral width core position & circulation
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: wake vortex characteristics retrieval
Doppler
spectrum
Radial velocity & spectral width
core position & circulation
Wind profile & TEDR
Circulation
Correction
Flow chart
Eg. Ascending scan WV
Left WV
Right WV
LoS velocity envelope

13. Radial velocity & spectral width core position & circulation
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: wake vortex characteristics retrieval
Doppler
spectrum
Radial velocity & spectral width
core position & circulation
Wind profile & TEDR
(a) WV core locations
(b) Before circulation correction
(c) After circulation correction
BH model fit using CDL measured data

14. Radial velocity & spectral width core position & circulation
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: atmospheric turbulence retrieval
Doppler
spectrum
Radial velocity & spectral width
core position & circulation
Wind profile & TEDR
Measurement geometry of RHI turbulence characteristics retrieval (Smalikho et al JAOT)
Transverse structure function and turbulence parameters

15. Radial velocity & spectral width core position & circulation
19th Coherent Laser Radar Conference, Okinawa, June
Methodology: atmospheric turbulence retrieval
Doppler
spectrum
Radial velocity & spectral width
core position & circulation
Wind profile & TEDR
(a)
(b)
(c)
(d)
standard deviation of velocity
crosswind velocity
turbulent energy dissipation rate
integral scale
Spatiotemporal distributions of the (a) standard deviation of velocity (m/s), (b) crosswind velocity (m/s), (c) turbulent energy dissipation rate (m2/s3) and (d) integral scale of turbulence (m) obtained from measurements by the CDL on Jan at BCIA

16. Qingdao 2014.02.26 Beijing 2014.03.5-6 Beijing 2014.07.14-15
19th Coherent Laser Radar Conference, Okinawa, June
Field campaigns: Beijing Capital International Airport BCIA 2014
One Trail test + Two field experiments
Qingdao
Beijing
Beijing

17. Field campaigns: Tianjin Binhai International Airport TBIA 2016
19th Coherent Laser Radar Conference, Okinawa, June
Field campaigns: Tianjin Binhai International Airport TBIA 2016
Prevailing wind direction in winter (from south to north), the airplanes during landing phase were detected.
Scan mode: continuous RHI (ascending + descending scan mode)
Scan elevation angle range: 5°-10° (height: 30-60m)
Scan azimuth direction: 94°
LOS range resolution: 30m
Blind area: 150m
range: m
Scan speed: 1°/s
Balance between WV finer structure and detailed WV evolution process!
Scanning strategies of the field observation campaign at TBIA

18. Field campaigns: Hong Kong International Airport HKIA 2016
19th Coherent Laser Radar Conference, Okinawa, June
Field campaigns: Hong Kong International Airport HKIA 2016
Scanning strategies
Lidar
Westerly wind
(left) spectral width (right) radial velocity. Time: 17:30:23-17:32:21 Aircraft type: A320
The schematic diagram of HKIA near ground effect observation and corresponding specification.
Date
Time Period
18:00-19:00
14:30-20:20
16:20-19:40
Elevation range 𝜽(°)
8-22
8-20
0-25
Detectable lowest height ∆𝑯（m）
~56
Elevation resolution ∆𝜽（°）
~1.2 ~5 ~1
Transverse range resolution ∆𝒙 (m)
~8.4
~35 ~7
horizontal distance
elevation evolution
(left) Wake vortex core position evolution process, y-axis represents the horizontal distance between the core position and the Lidar. (right) Wake vortex elevation evolution process.
good
bad

19. Field campaigns: BCIA 2017 A B
19th Coherent Laser Radar Conference, Okinawa, June
Field campaigns: BCIA 2017 A B
Field experiment at BCIA during Jan-Mar, A:wind profiler, B: Coherent Doppler Lidar

20. Experiment configurations and lidar parameters
19th Coherent Laser Radar Conference, Okinawa, June
Experiment configurations and lidar parameters
Specification
CDL
Wavelength (𝜆)
1.55 um
Pulse energy ( 𝐸 𝑝 )
150 uJ
Pulse repetition frequency ( 𝒇 𝒑 )
10 kHz
Pulse number (N)
1000
Pulse width ( 𝝉 𝒑 ) ns
LOS spatial resolution (∆𝑹)
15-30 m
Speed measurement range (V)
±30𝑚/𝑠
Speed measurement uncertainty (∆𝑣)
0.1 m/s
Distance to landing point A
974 m
Azimuth angle (𝝋)
𝟐𝟑𝟎 °
Distance to runway 36R ( 𝑹 𝒓 )
248 m
Distance between A and B
1110 m (H=55.5 m)
Sketch map of Lidar locations at BCIA

21. Experiment configurations: observation mode
19th Coherent Laser Radar Conference, Okinawa, June
Experiment configurations: observation mode
specific experimental parameters for RHI wake vortex detection
Configuration
Scanning rate ( 𝜔 𝑠 )
1 ° /s
Elevation range (𝜃)
- 1 ° ~ 13 °
Angular resolution (Δ𝜃)
0.2 ° ~ °
Detection range (R)
120 m ~ 600 m
Average time (Δ𝑇)
~0.3 s
Scan duration (T)
13 s ~ 14 s
Transverse resolution (Δ𝑥), R=300m
1.0 m ~ 1.6 m
Range depended
Detectable lowest height (Δ𝐻)
5 m ~ 6 m (building height)
Safe corridor
Lidar
WV tracing
Runway
The schematic diagram of BCIA near ground effect observation and corresponding specifications

22. Field campaign: aircraft records
19th Coherent Laser Radar Conference, Okinawa, June
Field campaign: aircraft records
Aircraft type
Weight
(M: medium, H: heavy)
Number
A319 M
A320
194
A321
952
A332 H
1056
A333
446
A343
825
A346 23
A359 4
A388 1
ARJ21
117
B737 59
B738
192
B744
1753
B752 39
B763 66
B772 89
B773
101
B777 64
B77L 3
B77W 18
B788
316
B789
165
C919
204
MD11 2
MD81/82/83
Statistical analysis:
Time period:
Position: BCIA 36R, landing phase
Total number: 6690
Airbus
Boeing
Others
Number, %
Heavy
1,416
999 1
2,416, 36.1%
Medium
2,202
2,070 2
4,274, 63.9%

23. Self-Adaptive Wake Vortex Simulation Model
19th Coherent Laser Radar Conference, Okinawa, June
Data processing flow of 2017 BCIA campaign
Self-Adaptive Wake Vortex Simulation Model
INPUT
OUTPUT

24. Near Ground Effect: Large Eddy Simulation, LES
19th Coherent Laser Radar Conference, Okinawa, June
Near Ground Effect: Large Eddy Simulation, LES
(a) Affected by crosswind
The wake vortex circulation LES simulation under near ground effect
(a) affected by crosswind
(b) unaffected by crosswind
(b) Unaffected by crosswind
courtesy: Prof. G. Cui, Dr. M. Lin
Tsinghua University
Lin et.al, AMM, 2016
Lin et. al, CJA, 2017
(b)
(c)
(d)
(a)
Dangerous area
boundary prediction
WV Lateral position
WV Altitude
Circulation

25. Data examples of 2017 BCIA campaign
19th Coherent Laser Radar Conference, Okinawa, June
Data examples of 2017 BCIA campaign
(a)
(b)
(c)
(d)
A333
A332
Trajectories of left (red squares) and right (black squares) wake vortex axes [(a), (c), (e)] and evolution of wake vortex circulation [(b), (d), (f)] generated by A333, A332, A332 aircraft over the BCIA at the following time:
23:02:17–23:05:52, 23 Jan 2017 [(a), (b)];
15:50:11-15:53:46 25 Jan 2017 [(c), (d)];
17:46:17–17:49:52, 25 Jan 2017 [(e), (f)]

26. Data examples of 2017 BCIA campaign
19th Coherent Laser Radar Conference, Okinawa, June
Data examples of 2017 BCIA campaign
[a] B788, 03:25:16 -03:31:51 Jan
[b] B788, 05:30:05 -05:36:40 Jan
(a)
(b)
(c)
(d)
(e)
(f)
(a)
(b)
(c)
(d)
(e)
(f)
Normalized parameters evolution process; (a) core distance; (b) Nadir angle; (c) Core altitude; (d) Vertical movement component; (e) Core horizontal distance; (f) Horizontal movement component

27. Normalized height range
19th Coherent Laser Radar Conference, Okinawa, June
Data examples of 2017 BCIA campaign
(a)
normalized vertical velocity
normalized height
(b)
Line
Normalized height range
1 green
0.2~0.4
2 light blue
0.4~0.6
3 orange
0.6~0.8
4 blue
0.8~1
5 pink
>1
6 red
all
Wake vortex behavior measured during BCIA 2017 campaign
(a): normalized height
(b): normalized vertical velocity
Solid line: luff wake vortex
Dash line: lee wake vortex

28. 19th Coherent Laser Radar Conference, Okinawa, June 18-21 2018
Summary & Outlooks
Summary: Real-time dynamic wake vortex tracking and characteristics under NGE with different scanning mode; Simultaneous observation of wake vortex and atmospheric turbulence
Outlooks: Wake vortex characteristics statistics under different atmospheric conditions; Decision-making system for aviation safety and to increase airport capacity
Acknowledgements:
P.28 Turbulence Characteristics during Typhoon
P.29 Wind Shear Observations at BCIA airport. P.30 UAV-borne CDL
P.32 Virtual tower and VAD Comparison