One of the primary noise sources for Open Rotor systems is the interaction of the forward rotor tip vortex and blade wake with the aft rotor. NASA has collaborated with General Electric on the testing of a new generation of low noise, counterrotating Open Rotor systems. Three-dimensional particle image velocimetry measurements were acquired in the intra-rotor gap of the Historical Baseline blade set. The velocity measurements are of sufficient resolution to characterize the tip vortex size and trajectory as well as the rotor wake decay and turbulence character. The tip clearance vortex trajectory is compared to results from previously developed models. Forward rotor wake velocity profiles are shown. Results are presented in a form as to assist numerical modeling of Open Rotor system aerodynamics and acoustics

Gui L.

Hill P.G.

Kool P.

Podboy G.

Soloff S.M.

Taylor J. R.

Wernet M. P.

Westerweel J.

Woodward

Wernet, Mark P.

VanZante, Dale E.

NASA Technical Reports Server

Tip Vortex and Wake Characteristics of a Counterrotating Open Rotor

Van Zante, Dale E.

20 
One of the primary noise sources for Open Rotor systems is 
the interaction of the forward rotor tip vortex and blade wake 
with the aft rotor. NASA has collaborated with General Electric 
on the testing of a new generation of low noise, counter-
rotating Open Rotor systems. Three-dimensional particle 
image velocimetry measurements were acquired in the intra-
rotor gap of the Historical Baseline blade set. The velocity 
measurements are of sufficient resolution to characterize the 
tip vortex size and trajectory as well as the rotor wake decay 
and turbulence character. The tip clearance vortex trajectory 
is compared to results from previously developed models. 
Forward rotor wake velocity profiles are shown. Results are 
presented in a form as to assist numerical modeling of Open 
Rotor system aerodynamics and acoustics. 
Tip Vortex and Wake Characteristics of a Counterrotating 
Open Rotor 
Dale E. Van Zante and Mark P. Wernet 
https://ntrs.nasa.gov/search.jsp?R=20120018036 2019-08-30T23:28:18+00:00Z
National Aeronautics and Space Administration 
www.nasa.gov 
Tip Vortex and Wake Characteristics of a Counterrotating 
Open Rotor  
Dale E. Van Zante and Mark P. Wernet ! 
48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & 
Exhibit and 10th International Energy Conversion Engineering 
Conference 
29 July - 1 August 2012 
Location: Atlanta, Georgia 
Presented by: Dr. Ken Suder 
Outline"
2 
•  Test Objectives and Approach"
•  Test Campaign Overview"
•  Stereo PIV setup in 9x15 tunnel"
•  PIV Results"
•  Tip Vortex trajectory"
•  Forward rotor wake profiles"
•  Summary"
Control room video monitor view of the laser 
sheet next to the Open Rotor test model in 
the 9x15 tunnel."
3 
Test Objectives and Approach"
OBJECTIVE  
•  Explore the design space for lower noise 
while maintaining the high propulsive 
efficiency from a counter-rotating open 
rotor system. "
OVERALL APPROACH 
•  Collaborate with GE  and  FAA/CLEEN 
program  to evaluate advanced  open 
rotor blade sets designed to minimize 
noise.  
•  Tests will be performed in the  NASA 9x15 
to measure noise and in the 8x6 transonic 
wind tunnel to validate performance.  
•  Installation effects such as pylon 
integration were also investigated. Rotating force balance 
The NASA Environmentally Responsible Aviation Project sponsored a 
detailed Open Rotor test series in the summer of 2010."
The ERA Diagnostics Test"
Acoustic 
Phased 
Array"
Farfield 
acoustics 
with Pylon"
Pressure 
Sensitive 
Paint"
Stereo 
Particle 
Image 
Velocimetry"
Acoustic 
Shielding"
The goal of the ERA Diagnostics Test was a comprehensive data set that 
will identify noise sources and enable improved performance and 
acoustic modeling of open rotor systems. 
The Stereo PIV measurements overviewed today are part of this 
comprehensive, detailed data set on Open Rotor aero and acoustics. 
5 
Test Campaign Overview"
History (1/3)"
6 
2009 
Aug                 Sep                  Oct                  Nov                  Dec 
Drive rig rehab 
and installation"
Drive rig checkout."
Sep 24 – Oct 27"
First research run."
Oct 28"
Linear array checkout."
Dec 7-11"
GE/Airbus entry start"
Dec 14"
History (2/3)"
7 
2010 
Jan     Feb     Mar     Apr     May     Jun     Jul    Aug     Sep      Oct     Nov    Dec 
GE/Airbus test 
complete."
Feb 12"
GR
C 
an
nu
al"
Fa
cil
ity
 S
hu
td
ow
n"
Drive rig muffler 
implementation."
FA
VO
R 
te
st 
(A
TP
)"
ERA Diagnostics Test."
Jul 19 – Sep 7"
Low Boom 
Inlet Test 
(SUP)"
Op
en
 R
ot
or
 In
sta
ll"
In
 th
e 
8x
6"
GE/Boeing test."
Apr 5 – 28."
History (3/3)"
8 
2011 
Jan     Feb     Mar     Apr     May     Jun     Jul    Aug     Sep      Oct     Nov    Dec 
Jan. 19, 2012"
End of Gen-2 
Test"
Ge
n-
2 
8x
6 
Te
st"
Au
g 
26
 –
 S
ep
 9
"
Gen-1 8x6 Test"
Feb 28 – Aug 25"
Force balance instrumentation issues."
Mar 9 and Apr 6"
8x6 Tare Runs"
Feb 9"
Gen-2 9x15 Test"
Nov 10 – Jan 19"
PIV Setup in the 9x15"
9 
Requirements and Constraints:"
•  Image the forward blade wake and tip 
vortex from the hub to outboard of the 
blade tip."
•  Image the maximum axial extent of the 
intra-blade gap without the laser sheet 
intersecting either the forward or aft blade."
To meet these requirements:"
1. The lasers were mounted on top of the 
test section."
2. The cameras were mounted in the walls."
The laser sheet was on the side of the 
model and parallel to the rotation axis."
laser 
Camera 1 
Camera 2 
Laser 
sheet 
PIV Setup in the 9x15"
10 
Laser "
window" Camera 1 "
window"
Camera 2 "
window"
Beam "
dump"
Further PIV details"
11 
Tip vortex track 
Measurements are phase locked to the forward rotor position."
Two phase angles were acquired for each pitch angle/rotor speed condition."
The aft rotor is at random position (not possible to sync both rotors/lasers/cameras)."
The width of the laser sheet was clipped 
at the lower span locations using a 
mechanical shutter."
This allowed the maximum axial 
measurement extent without hitting the 
blade with the laser sheet."
Smaller measurement plane 
spacing was used near the blade 
tip to capture the vortex with good 
radial resolution."
PIV Processing"
12 
Because each camera is mounted to a 
separate translation stage and views the 
light sheet plane through a different 
window – a unique 5-plane calibration 
was acquired for each of the 31 
measurement planes in the test matrix."
Flow seeding was done with Vicount 
5500 smoke generators for 0.2-0.3 μm 
particles."
Princeton Instruments ES-4020 cameras 
(2048x2048 pixels) were used to capture 
400 image pairs per plane."
The image data were processed with a NASA developed cross-correlation processing 
software called PIVPROC."
The software uses subregion image shifting and multi-pass correlation for improved 
spatial resolution. The measurements have an in-plane resolution of 1.43 mm."
Additionally, subregion distortion processing and Symmetric Phase Only Filtering (SPOF) 
correlation processing were used to further enhance the data set quality."
13 
PIV Results"
Tip Vortex Trajectory"
Vortex core location"
14 
Blade wake"
Tip vortex"
The vortex core is easily 
determined from a 
combination of in-plane 
streamlines and in-plane 
velocity vectors. "
Normalized Vortex Core Trajectory"
15 
z
N
-,I
N
t.lm
O.SS
O.Se
e.llS
e.ml
0.7_
e.?w
O.SS
e.4O
e.5S
! : !
i i : ! :
........................... ,.......... ;.......... _........ _................... . ......... ! .....................
A i : A i
A_ _ A & • :............• .........! ......i............: ...................
& : A. .
........2_. ............_ i. "
.................................. r _. ' "** ........ " '_ ......
A: DATA ,',REFERENCES 5 AND 6)
..............................--. CORRELATION ....
e.se i | i i i i i I t h i
o. ,._ ,._ ,.'_s :.oo _._
NORMALIZED AXIAL LOCATION, Zvtx/RtiD
Figure 10. Correlation and Data for the Trajectory of the Tip Vortex.
Linear-rational-function correlation methods (Reference 3) were used again to develop
an empirical relation for the trajectory of the tip vortex. Linear-rational functions are applica-
ble if the dependent variable shows a monotonic trend with the independent variable. Since
the radial movement of the tip vortex with axial distance is monotonic, approaching an asymp-
totic value, linear-rational function was chosen. The empirical relationship which yielded mini-
mum standard deviation is:
RWx = 12 (Zvtx)/Rti p + 1.0 (20)
Rti p 16 (Zvtx)/Rti p + 1.0
where
R,,tx: radial location of core of tip vortex
Zvtx: axial location of core of tip vortex.
Since the formulation for tip vortex discussed in Subsection -._ 1 uses br
Equation 20 is written in terms of b (see Figure 2 also):
b Rvt x 4 (Zvtx)/Rti p--r =i_--=
Rt_ p Rti p 16 (Zvtx)/Rti p +
1.0
= Rtip- Rvtx,
(2t)
£5 Of _¢o_ QUALITY
From Majjigi, et al" Current SPIV data"
The historical data correlated by Majjigi were based on helicopter in hover measurements."
The current measurements show a trajectory character that is linear with axial location."
16 
PIV Results"
Wake Character"
Wake profile locations"
17 
Note that the wake 
profiles are NOT along 
a constant radius."
Example wake profiles"
18 
Y, in
|W
|, f
t/s
-4-2024280
300
320
340
360
380
400
420 |W| for X=9.13, Z=-28, ft/s|W| for X=9.13, Z=-29, ft/s
|W| for X=9.13, Z=-30, ft/s
Y, in
Vr
, f
t/s
-4-2024-80
-60
-40
-20
0
20 Vr for X=9.13, Z=-28, ft/sVr for X=9.13, Z=-29, ft/s
Vr for X=9.13, Z=-30, ft/s
Axial Velocity"
Radial Velocity"
Blade wakes show an axial velocity deficit 
and an increased radial velocity relative to 
the core flow."
Note the streamtube contraction shows as 
a core flow negative radial velocity."
137 point resolution"
Summary"
19 
An extensive, unique calibration procedure and careful attention to the 
SPIV correlation processing has yielded very high quality data sets."
The tip vortex core trajectory shows a linear behavior with axial 
distance from the forward rotor tip."
The forward blade wakes show the typical turbomachinery wake 
behavior."
Acknowledgements:"
This research was sponsored by the NASA Environmentally Responsible Aviation 
Project."
The PIV measurement team included Randy Locke, Adam Wroblewski, and Gary 
Clayo. "
Csaba Horvath assisted with the figures presenting the PIV data."


Dale Van Zante

Mark Wernet

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Tip Vortex and Wake Characteristics of a Counterrotating Open Rotor

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