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SLD Simulation Capabilities with LEWICE
Mark PotapczukWilliam Wright
CFD Methods for SLD Simulation WorkshopScottsdale, AZ October 19-20, 2006
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Outline
SLD Requirements
SLD Icing Physics
SLD Modeling in LEWICE Reproducing SLD Cloud Conditions in the IRT
Numerical Simulation of Ice Shapes from a Bimodal LargeDroplet Icing Cloud
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SLD Requirements
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SLD Requirements
BACKGROUND
Requirements (or metrics) need to be defined to provide a "target" forSLD simulation in quantified terms Essential features or characteristics that need to be simulated How accurately characteristics need to be simulated
These requirements will be developed by means of sensitivity studies,either experimental or computational
Requirements take into account recommendations from the IPHWG onAppendix X
OBJECTIVES
Identify the metrics that have to be met to assure adequate simulation ofthe SLD environment from an engineering perspective
Provide assessment of how accurately these elements must besimulated
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SLD Requirements
APPROACH
Conduct sensitivity tests in SLD conditions to estimate threshold whereLWC, drop size, temperature errors have noticeable effect on thegenerated ice shape Attempt to develop / identify methodology to link aero effects to ice feature
changes
Conduct SLD Instrumentation Workshop to identify what current state-of-the-art is for water content and drop size instrumentation Estimates of measurement error
Operational issues affecting accuracy Identify research investments to mitigate measurement issues
Get feedback from user community on SLD requirements at SLD ToolsWorkshop Incorporate feedback into development of draft requirements document
Develop draft requirements document which includes parameters to besimulated, and required accuracies Consolidate results from tests & workshops
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OBJECTIVE - Determine the variation in icing cloud parameters necessary toproduce a measurable change in resulting ice accumulation
APPROACH Identify nominal SLD icing conditions (freezing fractions of 0.3 and 0.7) Determine the variant conditions (i.e. the amount of variation from the nominal
LWC, MVD, temperature) Measure and compare ice shape parameters for nominal and variant conditions
Geometric parameters Ice mass
STATUS 3 sensitivity tests completed Results reported in AIAA-2005-0073, AIAA-2006-0469 Methodology to define accuracy still under development (attempting to couple
MVD, LWC changes to ice shape to aero effects)
SLD Sensitivity Studies
InduceKnownSpray
Variations
Quantify Ice ShapeFeature Changes
Horn angleHorn Thickness
Characterize AeroEffect of Ice Feature
Changes
AssessSignificance
Of Aero ChangesBy ComparingTo knowledge
Base
Horn angleHorn Thickness
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Contour plot method used in 2004 /2005 sensitivity tests has potential tocharacterize the effect of smallchanges in LWC, MVD on ice shape Provide link between changes in spray
cloud and ice shape changes
Preliminary estimate of minimalchange LWC, MVD to produce changein ice shape
2006 test entry to confirmmethodology
SLD Sensitivity Studies
Ttot =7.9 F, T s = -1.6
F, 0=0.75, V=200 knots,AOA=2.5deg, 15 min spray
Contour Plot Showing Effect Of Change in MVD & LWC OnUpper Horn Thickness
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Follow-on aero testing
performed at UIUC
Contour plot method used in2004 / 2005 sensitivity testshas potential to characterizethe effect of small changes inLWC, MVD on aerodynamiceffects Provide link between
changes in spray cloud, iceshape changes, and aeroeffects
Preliminary estimate ofminimal change LWC, MVD
to produce change inaerodynamic characteristics Results are not yet published
SLD Sensitivity Studies
Contour Plot Showing Effect Of Change inMVD & LWC On Cl max
LWC
M V D
0.5 0.6 0.7 0.8 0.9 1 1.120
25
30
35
40
Clmax0.80.780.760.740.720.70.680.660.640.620.6
0.580.56
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SLD Icing Physics
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SLD Icing Physics
Background
Identify the physical processes of ice accretion that areimpacted by the presence of super-cooled large droplets.Quantify the important physical characteristics of the identifiedprocesses. Develop a database of information for developmentof models to be used in simulation software.
-20
-10
0
10
20
30
40
0 50 100 150 200 250
MVD ( m )
%
m
n = 0.3 n = 0.6 n = 0.9
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Approach
Investigate icing physics processes that arecharacteristic of SLD
Develop a thorough understanding of SLD icing physics
Provide data that will be useful in identifying necessarychanges to icing facilities or to measurement equipment
Provide data that will be useful in development of SLDmodels to be used in ice accretion codes
SLD Icing Physics
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Location Wichita State UniversityPrincipal Investigator Jason Tan & Michael Papadakis
Objective Identify droplet dynamic issues relevant to SLD icing
Droplet deformation & breakup prior to impact Droplet splash/deposition/bounce
Near-wall effects Supercooling large droplets LWC measurement of large MVD spray cloud
Status AIAA papers: 2003-0391 & 0392, 2004-0410, 2006-463
WSU Droplet Break-up Analysis
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Status Test completed July-August 2004
Results analyzed: AIAA 2005-0077, 2006-0466
Cranfield Droplet Splashing Research
Location - Cranfield UniversityPrincipal Investigators - David Hammond,
NASA, WSUObjective Characterize large droplet impact / splash
Quantify the incoming/splashed drop size, velocity,and angle
Measure the mass resulting from the splash process
Approach Use a low turbulence vertical tunnel to
accelerate droplets of known size toward atarget plate having a controlled water film
Quantify drop size, velocity, angle of impactsplash with high speed imaging methods
Correlate droplet impact/splash parameters
with mass splashed from target plate waterfilm
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Location Glenn Icing Research TunnelPrincipal Investigator Mark PotapczukObjective Determine whether large droplet
encounters result in mass loss
Ice Mass Measurements on Airfoils
SLD Mass Loss Experiment
-2
-1
-1
0
1
1
2
-2 -2 -1 -1 0 1 1 2 2
X (in)
Y ( i n
)
Clean airfoil20 microns40 microns70 microns100 microns
120 microns175 microns
Directly measure the mass of ice deposited on a well-definedtarget geometry under Appendix C and SLD conditions Method 1: maintain K 0, A c , and velocity over range of drop sizes Method2: maintain A c , , and freezing fraction over range of
model sizes and drop diameters
Determine ice shapes with LEWICE assuming no splashing Compare ice shape tracings to LEWICE results and compare
measured and calculated ice mass values AIAA paper 2003-0387
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Location NASA Glenn Icing Research TunnelPrincipal Investigator Michael PapadakisObjective Measure collection efficiency in SLD
SLD impingement on an MS-317airfoil (LEWICE vs. experiment )
SLD impingement on a NACA 65 2415airfoil (LEWICE vs. experiment)
Clean Geometry SLD Study
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Location NASA Glenn Icing Research Tunnel (US)Principal Investigator Michael Papadakis
ObjectiveMeasure collection efficiency in airfoils with existing iceshapes
Approach
Use existing blotter strip method for collection efficiencymeasurement on ice shape models
Status: Tests completed
FAA contractor report completed Dec. 2005
SLD Ice Shape Study
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WSU/NASA DrIFT ExperimentLocation Droplet Imaging Flow Tunnel (DrIFT)
Principal InvestigatorsMichael Papadakis, Jason Tan, Dean Miller
ObjectiveInvestigate imaging methods to studydroplet dynamics
Approach WSU re-design/fabricated tunnel inlet to facilitate droplet
dynamics experiments
Mono-dispersed droplet stream (44, 70,107, 160, 350 m)aimed at test articles Iced and un-iced NACA-0012 airfoil Multi-element airfoil
NASA high speed imaging techniques used to study dropletsplash and breakup
Phantom camera with optical backlighting Gated intensified camera with laser sheet
Status Testing conducted in July and Sept 2005 Qualitative imagery of droplet impact and breakup
obtained Data currently being analyzed
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SLD Modeling in LEWICE
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SLD Modeling in LEWICE
Background
Develop an interim model for SLD ice growth that can beadded to LEWICE. Develop a framework for introduction ofupdated SLD icing physics into models as they becomeavailable.
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Approach
Utilize the data from the SLD Icing Physics studies todevelop mathematical models that can be used incomputational tools such as LEWICE
Incorporate the models into the code and compare outputto SLD ice shape database
Document changes to LEWICE as models are developed
SLD Modeling in LEWICE
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Develop Droplet Breakup Model
Status Model has been incorporated into LEWICE 3.2.2 Thorough testing of model has been completed Upgrades to model can be included as more break-up testing
and modeling is conducted DVD of experimental ice shape and prediction comparison
available AIAA-2004-0412 ,AIAA-2005-1243 , AIAA-2006-0464
Location Glenn Research Center Principal Investigator William Wright
Objective Allow SLD droplet break-up to influence
ice shape developmentApproach Incorporate droplet dynamics model
into LEWICE and investigate influenceon ice shape development
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Develop Droplet Splashing Model
Status Model has been incorporated into LEWICE 3.0 Thorough testing of model has been completed
Upgrades to model can be included as more splashing testingand modeling is conducted DVD of experimental ice shape and prediction comparison
available AIAA-2004-0412, AIAA-2005-1243, AIAA-2006-0464
Location: Glenn Research Center Principal Investigator: William Wright
Objective Allow SLD droplet splashing to
influence ice shape developmentApproach Incorporate droplet splashing model
into LEWICE and investigate influenceon ice shape development
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Compare LEWICE Model to Mass Loss Data
Status Some initial comparisons have been conducted Mass agreement improved with droplet splashing
model added
Location Glenn Research Center
Principal Investigator William Wright,Mark Potapczuk
SLD Mass Loss Experiment
-2
-1
-1
0
1
1
2
-2 -2 -1 -1 0 1 1 2 2
X (in)
Y ( i n
)
Clean airfoil20 microns40 microns70 microns
100 microns120 microns175 micronsObjective
Identify strengths and weaknessesof SLD model
Approach Run LEWICE for conditions used indevelopment of SLD ice shapedatabase and compare ice shapes
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Droplet Trajectory and Impact
All physical effects modeled Turbulence
Saffman lift Bassett force (buoyancy) Gravity Drop deformation
Drop breakup Drop splashing Splashed drop trajectory
Impingement limit search for collection efficiency
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Drop Breakup Model
Drop breaks completely if We a > 13 Conservative assumption (drops take 2-3 cm to break
completely) Secondary drop size determined by empirical
relationship No experimental data available for validation
d s
d o= 6.2 w
a
14
Re d 1
2
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Splashing Model Requirements
Fraction of impinging mass ejected Size, velocity, angle of ejected drops
Tracking/re-impinging of ejected drops
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Current Model
Track one splashed drop for each incoming drop Use MVD of splashed distribution
Add splashed mass if drop re-impinges Drop-drop and drop-film interactions assumed part of
correlation
Asymptotic effects imposed when extrapolating
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Empirical Splashing Model (Part 1)
d sd o
= 8.72 e0.0281 K
V x,sV x,o
=1.075 0.0025 o
V y,s
V y,o= 0.3 0.002 o
( ) ( )
( )200*0092.0
1sin17.0
= n L
K
o
s
em
m
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Empirical Splashing Model (Part 2)
25.1
25.1Re*
==
w
nw
w
w d V d
OhK
Splash Threshold:
( )
200
sin
125.0
25.1
859.0
>
= LWC
K K l Ln
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Validation Data (Impingement)
NASA/WSU Impingement Database 19 geometries (7 ice shape geometries)
10 different MVDs (11 m - 236 m) 0 AOA 8 32 - 57 chord 175 mph (152 kts)
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LEWICE Impingement Runs
All conditions were computed with 4 options: Potential flow, no splashing (PF-NS) Potential Flow, splashing (PF-S) Navir-Stokes, no splashing (NS-NS) Navir-Stokes, splashing (NS-S)
All cases use 27-bin drop size
Grids for Navir-Stokes generated with ICEG2D option Grid refinement performed on high AOA cases only
WIND 5.0 used as Navir-Stokes solver Spalart-Allmaras turbulence model used 27 solutions needed for impingement cases
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Impingement Parameters Compared
Maximum Beta Results also compared to scaling method
Total Water Catch
Upper and Lower Impingement Limits Measured from leading edge as a percent chord
Upper and Lower Location where = 0.1 Occasionally used for sizing de-icing equipment
dsW V LWC m = ***&
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GLC305 AOA=6, MVD=92
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
-0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1
s/c
C o
l l e c t
i o n
E f f i c i e n c y LEWICE SLD
ExperimentLEWICE 2.0
Typical Splashing Results
Maximum Beta
LowerImpingement Limit
Upper Impingement Limit10% Limits
N i l A i d S Ad i i i
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Validation Data (Ice Shapes)
3017 IRT Ice Shapes 3049 LEWICE Runs
944 Appendix C conditions
682 SLD conditions ran with three options Monodisperse MVD 27 bin distribution (no splash) 27 bin distribution (with splash)
9 Different geometries Time: 0.5 to 69.7 min (scaled condition) Chord: 1.5 (cylinder) to 78 in Velocity : 65 to 323 kts (0.19*10 6 < Re < 14.6*10 6) LWC: 0.3 to 2.8 g/m 3
MVD: 12 to 305 m Temperature (total): -20 to 34 F
N ti l A ti d S Ad i i t ti
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Icing Parameters Compared
Icing Limit Upper & lower
Horn Height Upper & lower
Stagnation freezing fraction Leading edge minimum thickness
Horn Angle Upper & lower
Iced Area
Ice Weight (if measured)
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Overall Comparison
Parameter Averages
0
10
20
30
40
50
60
70
80
90
100
overall rime mixed glaze
% C h o r d
D i f f e r e n c e
f r o m
E x p .
LEWICEExperimentSLD LEWICEDistributionDistribution & Splash
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HF1012936
-5.0
-4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
-4.0 -2.0 0.0 2.0 4.0 6.0 8.0 10.0
x, in.
y ,
i n
Lewice ice shape lewice limits icing limits
Typical Icing Results
Chord = 36 V = 175 kts AOA = 4 T o = 30.5F
LWC = 0.54 g/m3
MVD = 20 mTime = 22.5 min GLC305 Airfoil
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p
www.nasa.gov
AE1168136
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
-1.5 -0.5 0.5 1.5 2.5 3.5
x, in.
y ,
i
Lewice ice shape lew upper horn lew lower horn
icing upper horn icing lower horn lewice limits icing limits
Typical SLD Results
Chord = 21 V = 100 kts AOA = 0 T o = 4.2 F
LWC = 1 g/m 3 MVD = 120 mTime = 9.4 min NACA0012 Airfoil
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AE1193336
-2.5-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-1.5 -0.5 0.5 1.5 2.5 3.5 4.5 5.5
x, in.
y
, i
Lewice ice shape lew upper horn lew lower horn
icing upper horn icing lower horn lewice limits icing limits
Need Feather Model?
Chord = 21 V = 200 kts AOA = 0 T o = 20 FLWC = 0.5 g/m3 MVD = 160 mTime = 16.9 min NACA0012 Airfoil
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Reproducing SLD
Conditions in the IRT
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Reproducing SLD Conditions in the IRT
Background
Determine the characteristics of SLD icing conditions that must
be reproduced in a ground based icing facility. Identify the range of SLD conditions that can be produced using
the current capabilities of the IRT.
Develop methods for reproducing characteristics of in-flightSLD icing conditions that cannot be simulated currently.
Document those characteristics that cannot be reproduced inthe facility in its current configuration.
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Reproducing SLD Conditions in the IRT
Approach
Assess current capability to produce SLDWhat set or range of icing conditions can be produced in an icing tunnelwith current spray system technology
Investigate and document constant or time varying icingconditions in natural SLD encounters
Examine the data from SLD in-fl ight encounters and characterize the cloudand flight condi tions for an SLD ice shape
Develop SLD cloud simulation methodCreate operating conditions in the IRT that produce a cloud similar to thatfound in natural SLD encounters by altering spray times and conditions
Document Range of LWC and MVD vs. Appendix X Document drop size distribution vs. Appendix X
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Location Glenn Research Center
Principal Investigators Dean Miller, Mark Potapczuk, RobertIde, & John Oldenburg
Objective
Attempt to generate a Bi-Modal SLD spray cloud in an icingtunnel
Approach
Sequentially spray a small drop (20 m MVD) condition,then a large drop (130 m MVD) condition
Maintain freezing fraction for both conditions Vary order / time of spray conditions Generate a sequenced ice shape Document ice shape with ice tracings and photographs
Develop SLD Cloud Simulation Method
Compare sequenced SLD ice shape to ice shape generated from non-sequenced 20 m MVD or 130 m MVD icing spray
Status
2 tests completed, reported in AIAA-2005-0076, AIAA-2006-0462
Currently investigating another alternate technique
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Alternate method underdevelopment Sequencing not required
Utilizes existing IRTnozzles Adds hydraulic (water
only) nozzle Preliminary results
suggest can match bi-modal cases with flatarea in cumulative LWCcurve
Prototype nozzles underevaluation Engineering issues to be
resolved
Develop SLD Cloud Simulation Method
Target SLD Spectra
00.10.20.30.40.50.6
0.70.80.9
1
1 10 100 1000Drop Diameter, (um)
C u m
M a s s F r a c t
i o n
16.4 20a10dp SUM MSC2 Boeing1
Cumulative LWC From SimultaneousSpray (Mod-1 & Hydraulic Nozzle)
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SLD Cloud Uniformity in the NASA IRT
Principal Investigators - JackOldenburg and Mark PotapczukObjectives Icing Research Tunnel (IRT)
enhancements to improve SLDuniformity allowing a broader range
of icing test possibilities under SLDconditions.
Future SLD experiments willproduce more reliable and robustdata than has been previouslyavailable.
Description Six columns of vertical airfoil shaped struts were added to the IRT spray bars Improved LWC uniformity. Increased the performance capabilities of the tunnel Increased the confidence level of the cloud operational characteristics Enhancements to SLD uniformity will allow a broader range of icing test possibilities
Status All work for the experiment is done and has been satisfactory evaluated- March
2006
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Numerical Simulation of IceShapes from a Bimodal
Large Droplet Icing Cloud
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Target SLD Spectra
0
0.2
0.4
0.6
0.8
1
1 10 100 1000
Drop Diameter, ( m)
C u m
M a s s
F r a c t
i o n
MVD50 22 171.5 SUM
Droplet Distribution for ZLE with MVD > 50 m
National Aeronautics and Space Administration
LEWICE droplet distribution for MVD > 50 m
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12.5 30.5 61.75 135 225 315 405 567 850.50.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
f r a c
t i o n a
l L W C
LEWICE droplet distribution for MVD > 50 m
Droplet Diameter, ( m)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
1 10 100 1000
Drop Diam. ( m)
C u m .
% L
W C
National Aeronautics and Space Administration
Component Spr s of Bi mod l Seq encing
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-5
0
5
10
-5 0 5 10 15X, in
Y , i
n
Airfoil171.5 microns22 microns
171.5 micron MVD:
LWC = 0.878 g/m 3
22 micron MVD:
LWC = 1.3 g/m 3
Common conditions:V = 150 knots
Ts = 17 F
Time = 20 min.
Component Sprays of Bi-modal Sequencing
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Component Sprays of Bi modal Sequencing
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171.5 micron MVD
LWC = 0.878 g/m 3
22 micron MVD
LWC = 1.3 g/m 3
Common conditions: V = 150 knots, Ts = 17 F, Time = 20 min.
Component Sprays of Bi-modal Sequencing
National Aeronautics and Space Administration
Ice Shapes Produced by Sequencing
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-5
0
5
10
-5 0 5 10 15X, in
Y , i
n
Airfoil171.5, 22 microns22, 171.5 microns
171.5 micron MVD:
LWC = 0.878 g/m 3
t = 4 min.22 micron MVD:
LWC = 1.3 g/m 3
t = 1 min.Common conditions:
V = 150 knots
Ts = 17 FTtotal = 20 min.
Ice Shapes Produced by Sequencing
National Aeronautics and Space Administration
Ice Shapes Produced by Sequencing
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171.5 - 22 micron 22 171.5 micron
Common conditions: V = 150 knots, Ts = 17 F, Time = 20 min.
Ice Shapes Produced by Sequencing
National Aeronautics and Space Administration
LEWICE Results for Large-Small Sequence
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171.5 micron MVD:
LWC = 0.878 g/m 3
t = 4 min.22 micron MVD:
LWC = 1.3 g/m 3
t = 1 min.Common conditions:
V = 150 knots
Ts = 17F
Ttotal = 20 min.
LEWICE Results for Large Small Sequence
-5
0
5
10
-5 0 5 10 15X, in
Y , i
n
Airfoil171.5, 22 micronsLEWICE dist.LEWICE seq.
National Aeronautics and Space Administration
LEWICE Results for Small-Large Sequence
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171.5 micron MVD:
LWC = 0.878 g/m 3
t = 4 min.22 micron MVD:
LWC = 1.3 g/m 3
t = 1 min.Common conditions:
V = 150 knots
Ts = 17F
Ttotal = 20 min.-5
0
5
10
-5 0 5 10 15X, in
Y , i
n
Airfoil22, 171.5 micronsLEWICE dist.LEWICE seq.
LEWICE Results for Small Large Sequence
National Aeronautics and Space Administration
Conclusions (1)
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Conclusions (1)
Icing physics studies conducted on large dropletbreak-up, splashing, and re-impingement
Mass loss experiments performed suggesting effect
of splashing at all drop sizes Quantitative analysis shows that LEWICE
impingement results with splashing are comparableto experimental accuracy Average difference less than 30% for all parameters
Splashing model improves impingement limit but notnecessarily icing limit results in SLD regime
Splashing model more likely to under predict results Effects much less pronounced in 3.2
National Aeronautics and Space Administration
Conclusions (2)
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Conclusions (2)
Experimental methods under development toreproduce bi-modal droplet distributions
LEWICE reproduces bi-modal ice shapes very well
LEWICE results show little difference betweensequenced spray and actual bi-modal ice shape