Document
Turbulence Modeling in Aircraft Icing
N94-
Mark G. Potapczuk Icing & Cryogenic Technology Branch Workshop on Computational Turbulence Modeling NASA ICOMP September 15, 1993
INTRODUCTION
The Icing and Cryogenic Technology Branch develops computational tools which predict ice growth on aircraft surfaces and uses existing CFD technology to evaluate the aerodynamic changes associated with such accretions.
Surface roughness, transition location, and laminar, transition, or turbulent convective heat transfer all influence the ice growth process on aircraft surfaces.
Turbulence modeling is a critical element within the computational tools used both for ice shape prediction and for performance degradation evaluation.
CURRENT CODE DEVELOPMENT
2D CODES • LEWICE/IBL - POTENTIAL FLOW / INTERACTIVE BOUNDARY LAYER 3D CODES • LEWICE3D - PANEL CODE / INTEGRAL BOUNDARY LAYER • LEWICE3DGR - ANY GRID BASED FLOW SOLUTION
ICE ACCRETION MODELING
CURRENT MODEL USED FOR ICE GROWTH MASS AND ENERGY BALANCE IN CONTROL VOLUMES ALONG THE SURFACE CONVECTIVE HEAT TRANSFER IS MAJOR FACTOR IN ENERGY BALANCE INTEGRAL BOUNDARY LAYER FORMULATION USED TO DETERMINE LAMINAR AND TURBULENT HEAT TRANSFER COEFFICIENTS SURFACE ROUGHNESS MODELED AS SAND-GRAIN ROUGHNESS; ACTUAL ICE ROUGHNESS VARIES FROM SMALLER TO LARGER THAN BOUNDARY LAYER THICKNESS
ICE ACCRETION MODELING
CONVECTIVE HEAT TRANSFER MODEL USED FOR ICE GROWTH SKIN FRICTION COEFFICIENT
(864"00t 11-2
cf2 = 0"16811
ln_, _ +2.568
WHERE 0.8
o (s)
t
0.0156 j.s V3.86 ds ] + 0 t (Str)
V4.11 Str e e
ICE ACCRETION MODELING
CONVECTIVE HEAT TRANSFER MODEL USED FOR ICE GROWTH LAMINAR
h (s) = 0.296_ [,,--2.88_s,,1.88,V e JOVe as!1-1/2
TURBULENT
[ ct2 ]
ht(s ) = StpVeC p = Prt+ c_-(1/St k) PVeCp
ICE ACCRETION MODELING
CONVECTIVE HEAT TRANSFER MODEL USED FOR ICE GROWTH ROUGHNESS STANTON NUMBER -0.2 Vrk s
St k = 1.16 (---_)
AND V = Ve_C/2
ICE ACCRETION MODELING
ICE ROUGHNESS CHARACTERIZATION SAND-GRAIN ROUGHNESS ACTUAL ICE ROUGHNESS
ICE ACCRETION MODELING
PLANS • EXPERIMENTS TO CHARACTERIZE ICE ROUGHNESS GEOMETRIES AT A VARIETY OF ICING CONDITIONS • EXPERIMENTS TO CHARACTERIZE VELOCITY FIELD OVER REAL AND ARTIFICIAL ICE ROUGHNESS GEOMETRIES • EXPERIMENTS TO MEASURE HEAT TRANSFER OVER REAL AND ARTIFICIAL ICE ROUGHNESS GEOMETRIES • DEVELOPMENT OF MODIFIED COMPUTATIONAL MODEL BASED ON THESE EXPERIMENTS
ICED AIRFOIL AERODYNAMICS
NACA 0012 ICING CONDITIONS 4 = o_ = V = 130 mph d = 20oP.m LWC = 2.1 g/m 3 SHEAR LAYER T 18 F RECIRCULATION REGION 5 MINUTE ICE GROWTH
ICED AIRFOIL AERODYNAMICS
BALDWIN-LOMAX TURBULENCE MODEL Inner Layer _tt - I2 ( Uy - Vx ) l l = mixing length Outer Laver _1, t - FmaxYma x
F (y) = y 03 ( 1 - exp ((-y*)/A) )
ICED AIRFOIL AERODYNAMICS
BALDWIN-LOMAX TURBULENCE MODEL NORMAL B.L. F PROFILE RECIRCULATION REGION F PROFILE Fmax
f
F F Ymax Y Y
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL WHERE y+Ay --<C 1 l(y) = K-_2y 1- 1 _ 1-e Y J Y AND WHERE y + _Xy CI • --r- > Cl l (y) = _:-C22 y y
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL l=Ky | C| o | | ---! y --, ClY* , V V
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL THE CEBECI-CHANG ROUGHNESS MODEL IS ADDED TO THE TURBULENCE MODEL
5 <k + <70
S
.9[
0.58
0.7 (ks +) 70 < k+s < 2000
WHERE,
AY + = (4) (ux/V) and k +s = ks (u,/v)
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL C L vs. o_ 1.0 O -- Bragg, [66] Z_ -- ARC2D, MML model 13 -- ARC2D, B-L model 0.8 C L J O.6 fJ 0.q" 0.2
_/_
/
(" I I I ! I I I I I I 0.0 0 2 _ 6 8 10 AOA
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL C D vs.
.2o o -- Bra_, [66] _. -- ARC2D, MML model D _ ARC2D, B-L mode] .16 /- / O ./ c D / / l' .12 o#
x
/ / t' / / .." J .08 - / / ...1_ ../ 0
.o_ L J."1_Z "
t I T _ I O0 _0 ) I ) ) ) , " 2 _ 6 8 10 AOA
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL STRUCTURED GRID FOR ARTIFICIAL ICE SHAPE c_ _u B ),_ 8" ....,+-- O,OS O,IS 0.20 -0. I0 "0,05 0.00 0.10
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL UNSTRUCTURED GRID FOR ARTIFICIAL ICE SHAPE m -0.05 0.00 0.05 0.10 0.15 0.20
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL STRUCTURED GRID MACH NUMBER CONTOURS O. 120 M.
1.40w]O' Re 215x50 GRID ' ol -0.10 0115 0.20 -0.05 O.CO 0.05 10
ICED AIRFOIL AERODYNAMICS
MML TURBULENCE MODEL UNSTRUCTURED GRID MACH NUMBER CONTOURS 0.I20 M.
4.00" o 1.40_I0' Re
CONCLUDING REMARKS
• TURBULENCE MODELING PLAYS A ROLE IN ICE GROWTH PREDICTION AND IN PERFORMANCE EVALUATION • NEW MODELING IS REQUIRED FOR THE LARGE ROUGHNESS ELEMENTS OF A TYPICAL ICE ACCRETION • AN EXPERIMENTAL PROGRAM IS CURRENTLY UNDERWAY TO DEVELOP A DATABASE FOR CREATION OF SUCH A MODEL • AN ALTERNATE ALGEBRAIC TURBULENCE MODEL HAS BEEN USED TO EVALUATE PERFORMANCE DEGRADATION DUE TO ICING THE MML MODEL HAS BEEN USED IN AN UNSTRUCTURED GRID NAVIER-STOKES CODE TO CALCULATE FLOW OVER AN ARTIFICIAL ICE SHAPE