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0 Computational Modeling of Ice Cracking and Break-up from Helicopter Blades Shiping Zhang, Habibollah Fouladi, Wagdi G. Habashi CFD Lab, McGill University,

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Presentation on theme: "0 Computational Modeling of Ice Cracking and Break-up from Helicopter Blades Shiping Zhang, Habibollah Fouladi, Wagdi G. Habashi CFD Lab, McGill University,"— Presentation transcript:

1 0 Computational Modeling of Ice Cracking and Break-up from Helicopter Blades Shiping Zhang, Habibollah Fouladi, Wagdi G. Habashi CFD Lab, McGill University, Canada Rooh Khurram King Abdullah University of Science and Technology (KAUST), Saudi Arabia

2 1 Introduction Ice accretion on wings Business jet with aft-mounted engine Ice impact on engine blade Helicopter Hence it is very important to know where and how ice breaks up ! Air crash happened in 1991 in Stockholm due to ice ingestion

3 22 Background Scavuzzo, University of Akron, experiments on impact ice mechanical properties and qualitative analysis for 2D ice break up R.J. Scavuzzo, M.L. Chu, C. J. Kellackey, Impact ice stresses in rotating airfoils, J. Aircraft, 28(1991), Brouwers, The Pennsylvania State University, developed a quasi-3D model on ice shedding for helicopter blades E. W. Brouwers, J. L. Palacios, E. C. Smith, A. A. Peterson, The experimental investigation of a rotor hover icing model with shedding, AHS 66th Annual Forum and Technology Display, Phoenix, USA, Most previous research on ice shedding are qualitative 2D analyses, and no fully 3D ice break up analyses have been done. The object of this study is thus to develop 2D and 3D simulation tools to quantitatively predict where and how ice breaks.

4 Mechanical properties of ice PropertyUnitsValue Young ’ s modulus, E N m ×10 9 Bulk modulus, BN m ×10 9 Shear Modulus, GN m ×10 9 Poisson ’ s ratio, υ n/a0.325 Schematic stress-strain curves I, II, and III denote low-,intermediate-, and high-strain rates Elastic properties of homogeneous poly-crystalline isotropic ice at -16ºC At low strain rate, ice shows ductile behavior due to rheological property At high strain rate, for example during crack propagation process, it behaves as a brittle material Tensile strength: MPa (-10ºC ) Compressive strength: 5-25 Mpa (-10ºC) Adhesive strength with aluminum, MPa, at -11ºC

5 4 Framework of ice break-up modeling Airflow Solution Droplet Solution Ice Accretion Mesh Generation Stress Analysis Crack Propagation

6 5 Mathematical model of ice under fluid forces The Navier-Stokes equations in conservation form are: The viscous stress tensor is defined as: The equations of equilibrium and the motion for the structure are: Fluid mechanics Solid mechanics Interface conditions

7 Crack propagation Continuous fracture modes Crack opening sliding tearing

8 7 Crack propagation Quarter-point elements Quadrilateral quarter-point elements Triangle quarter-point element The standard Lagrange second order shape functions of 1D quadratic element Standard, polynomial geometry interpolation scheme Standard, polynomial displacement interpolation scheme Parametric Space (a) Cartesian Space (b)

9 8 2D crack propagation Quarter-point elements The unusual case of ¼-point geometry Substitute (3) into standard polynomial displacement interpolation scheme (3) Differentiating the displacement field, strain in the element Singular term Parametric Space (a) Cartesian Space (b) Unexpected, non-polynomial interpolation Standard, polynomial geometry interpolation scheme Standard, polynomial displacement interpolation scheme (2) (1)

10 9 2D crack propagation Quarter-point elements P1 distribution of quarter-point element P1 distribution of normal quadratic element

11 10 2D crack propagation Quarter-point elements P1 distribution in the vicinity of crack tip of quarter-point elements P1 distribution in the vicinity of crack tip of normal quadratic elements

12 11 2D crack propagation Quarter-point elements Principal stress I distribution in 3D of quarter-point elementPrincipal stress I distribution in 3D of normal quadratic element

13 12 2D crack propagation Evaluation of stress intensity factor (SIF) Displacement correlation method is adopted for extracting SIF’s from local field information Evaluation of propagation direction The direction of crack is based on the Hoop Stress Criterion For plain stress, only replace with

14 13 2D crack propagation Benchmark study Plan strain condition Propagation steps: 32 Problem description The single edge cracked plate under far field shear loading reference result [Alshoaibi] present code

15 14 Results of 2D ice break-up from airfoil Mesh of fluid domainPressure field Induced stress distribution Induced stress and crack

16 15 Results of 2D ice break-up from airfoil Crack propagation: Re-meshing (left) P1 stress distribution (right) (quasi-static process, time term is not considered)

17 16 Results of 2D ice break-up from airfoil Comparison with Franc 2D Franc 2D’s resultIn-house Code’s result

18 17 3D crack propagation Tracking 3D crack propagation fronts The direction of crack is based on the Principal Stress Criterion, the crack propagates into the direction normal to the direction of maximum principal stress Calculating maximum principal stress and its direction Propagation direction Crack growth increment

19 18 3D crack propagation Validation of 3D crack propagation package Three point bending test with the initial crack of an inclined plane ) Three points bending test, with initial crack of an inclined plane with angle of 45 degree. The load force is applied at the middle of the specimen

20 19 3D crack propagation Validation of 3D crack propagation package 3D out of plane crack propagation

21 20 3D crack propagation Validation of 3D crack propagation package Top view of reference resultsTop view of in-house code results

22 3D ice break-up analysis for helicopter blades Ice accretionIce shape identification Meshing Stress analysisInterfacial separation Crack propagation

23 22 3D ice break-up analysis for helicopter blades Ice accretion Caradonna hover test case used for flow solution Ambient temperature of -19°C Liquid water content (LWC) of 1 g/m 3 Droplet mean value diameter (MVD) of 20 microns NACA 0012 airfoil, two untwisted blades Time: 120 seconds Ice shape identification Mesh of iced blade Mesh of clean blade Meshing Closed surface mesh Unstructured tetrahedral elements generated by TetGen Stress analysis According to reference, the aerodynamic force could be negligible compared with centrifugal force

24 23 3D ice break-up analysis for helicopter blades ice-airfoil interface bond breaking Cut section stress distribution of principal stress 1 Ice tensile strength: 0.7 to 3.1MPa at -10ºC Ice-Aluminum interface adhesion strength: 0.3 to 1.6MPa at -11ºC Edge refinement based on the first derivative of interest value is done to capture the interface bond and de-bonded transition zone Bond separation Mesh adaptation

25 24 3D ice break-up analysis for helicopter blades Crack initiation and propagation Figure 14. Crack propagation process Evolution of crack (left) and principal stress 1 (right) during the interface bond breaking and crack propagation process

26 25 Summary Employing a fracture mechanics framework, 2D and 3D crack propagation methodologies were developed A thorough validation study of the two approaches is made The 2D and 3D crack propagation are integrated seamlessly into FENSAP-ICE, providing the flow, impingement, ice accretion, mesh generation, stress analysis and crack propagation automatically, and making it the first to have the capability to quantitatively simulate and analyze the 2D and 3D ice break-up and shedding from airplane wings and helicopter blades 2D ice break-up from wings of aircraft and 3D ice break-up from helicopter blades are analyzed for typical flow, icing, and operating conditions. The exact location of ice initial cracking, the crack propagation and the shed ice shape are obtained, which could be used in the future for ice shedding and impact analysis

27 26 Future work The ice break-up methodology will be coupled with rotor blade vibration analysis, de-icing, ice shedding trajectory and impact simulations. Ice break-up package will be used to predict ice shedding from wind turbine and power cables

28 27 Thank you!


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