Streamlining Aircraft Icing Simulations D. Snyder, M. Elmore
Industry Analysis Needs / Trends Fidelity Aircraft Ice Protection Systems-Level Modeling Optimization
Background Ice accretion can critically alter performance – Aerodynamic performance of wings – Engine performance due to inlet icing – Improper readings from instrumentation Aircraft must be certified to fly in certain icing conditions Simulation is important – Designing and estimating performance of ice protection systems – Estimating how ice accretion affects aircraft performance
Icing Topics Thermal Ice Protection Systems • Internal/External Flow • Conjugate Heat Transfer • Collection Efficiency Ice Accretion • Fluid Films • Ice Shapes (2D / Pseudo-2D / 3D) • Aerodynamic Performance Degradation Common industry practice is to use a separate code for each of the above steps – Slow, cumbersome, expensive, prone to errors (mapping, translation, etc.)
STAR-CCM+: Streamlining The Process Thermal Ice Protection Systems 3D Internal/External Flow Droplet Impingement & Distribution Formation of Fluid Film Conjugate Heat Transfer Runback/Evaporate Fluid Film Ice Accretion & Aerodynamic Performance One Tool Flowfield (3D Navier-Stokes) One Model Dispersed Phase One Process Fluid Film Freeze/Melt Update Ice Shape Mesh Morph / Remesh
Unified Process: Thermal Ice Protection Systems 3D Internal/External Flow Droplet Impingement & Distribution Formation of Fluid Film Conjugate Heat Transfer Runback/Evaporate Fluid Film 6
Example: Piccolo Tube Internal/external flows with complex geometry – Simultaneous, coupled solution of internal and external flowfields – Piccolo tubes, jet orifices, leading-edge cavity, etc. Conjugate heat transfer – Simultaneous, coupled solution for fluid and solid thermal Wing Skin Holes Piccolo Tube
3D Droplet Modeling Lagrangian Multiphase (LMP) – Individually track particles – Can be run fully coupled with flowfield or with frozen flowfield – Injection locations are arbitrary and customizable Dispersed Multiphase (DMP) – Lightweight one-way-coupled Eulerian approach – Better model of the cloud than LMP • Concentration is solved everywhere in the flowfield • Shadow zones identified – Can be run fully coupled with flowfield 16.45 μ m or with frozen flowfield 20.36 μ m – No injection locations: particles exist throughout the freestream flow
Dispersed Multiphase Model (1/2) Continuous treatment of the subcooled droplets Conservation equations solved in a segregated manner Continuity Momentum Energy Multiple phases can exist simultaneously to represent distributions of droplet properties – E.g. Langmuir-D Distribution
Dispersed Multiphase Model (2/2) One-way coupled – Background flowfield influences droplets but not vice versa – Drag (Schiller-Naumann) – Pressure Gradient Force – Heat Transfer (Ranz-Marshall) Update of dispersed phase on instantaneous frozen background – Collection efficiencies as a post-processing step – Multi-shot icing simulations Compatible with many models and numerical schemes – Impingement onto fluid films – Segregated or Coupled solver for background flow – Lagrangian (stripping or simultaneous modelling of SLD's)
DMP Collection Efficiency GLC-305 Airfoil α = 1.5 α = 6.0
DMP Collection Efficiency 737 Inlet: Mesh & Setup Solver Setup Physics Conditions – 3D Segregated Solver – 0° AoA – V∞ 75 m/s – Steady – K- ω SST turbulence – Static temperature 7.0 C – Dispersed Multiphase – Static pressure 95.840 kPa – Particle diameter 20.36 μm – Compressor face MFR 7.8 kg/s
DMP Collection Efficiency 737 Inlet: Contours
DMP Collection Efficiency 737 Inlet: Validation
DMP Collection Efficiency 737 Inlet: Validation
DMP Collection Efficiency 737 Inlet: Validation
DMP Collection Efficiency 737 Inlet: Productivity • Import 737 inlet STL 5 Minutes • Create domain, name faces Surface Preparation • Man-Time: 5 minutes • Machine Time: N/A • Trim volume mesh with prism layers 3.5 • Mesh size: 2.1M cells Meshing Minutes • Man Time: 2 minutes • Machine Time: 1.5 minutes on 1 CPU • Define physics conditions 30 • Define BCs Solving • Man Time: 10 Minutes Minutes • Machine Time: 20 minutes on 16 CPUs • Define Collection Efficiency FFs • Export data for use with Excel Post- 5 Minutes processing • Man Time: 5 minutes • Machine Time: N/A
Unified Process: Ice Accretion Flowfield (3D Navier-Stokes) Dispersed Phase Single Shot Multi-Shot Fluid Film Freeze/Melt Fully Transient Update Ice Shape Mesh Morph / Remesh
Fluid Film Example: Runback Capabilities – Droplet deposition from DMP / LMP – Run-back – Heat transfer – Freeze / Thaw / Evaporation / Sublimation – Edge- and wave-based stripping to LMP
Melting-Solidification Model (1/2) Based on an Enthalpy balance formulation for the film
Melting-Solidification Model (2/2) Within a timestep, iteratively finds the mass that freezes by repeatedly: – Computing a relative solid volume fraction (based on water temperature) • 0 above 273.15K • 1 below 273.15K – Updating the thickness of film to be removed in timestep – At convergence, either • All liquid film is removed (rime conditions) or • There is a liquid remainder at 273.15K (glaze conditions) – Morph the solid boundary according to newly formed ice • Optional smoothing
Approaches to Ice Accretion Analysis Single-Shot – Frozen flowfield during ice buildup Multi-Shot – Frozen flowfield, updated periodically during ice buildup Fully Transient – Flowfield updated at each time step throughout ice buildup – Approximately 2x the computational cost of single-shot
Validation: 2D CT Airfoil – Geometry
Validation: 2D CT Airfoil – Icing Tunnel
Validation: 2D CT Airfoil – Run 142: 2 Minutes Commercial Transport Airfoil – Mach 0.45 – Airspeed 285 kts – AoA 0.0 – T static -18.1 C – 0.100 g/m 3 LWC – 2 minutes
Validation: 2D CT Airfoil – Run 112: 6 Minutes Commercial Transport Airfoil – Mach 0.45 – Airspeed 282 kts – AoA 0.0 – T static -15.4 C – 0.285 g/m 3 LWC – 6 minutes
Validation: 2D CT Airfoil – Run 106: 6 Minutes Commercial Transport Airfoil – Mach 0.45 – Airspeed 279 kts – AoA 0.0 – T static -20.2 C – 0.295 g/m 3 LWC – 6 minutes
Validation: 2D CT Airfoil – Run 107: 22.5 Minutes Commercial Transport Airfoil – Mach 0.45 – Airspeed 279 kts – T static -20.2 C – AoA 0.0 – 0.295 g/m 3 LWC – 22.5 minutes
STAR-CCM+ Icing Simulation Summary STAR-CCM+ V9.02 provides a streamlined process for performing various aircraft icing related simulations Benefits – Fully 3-Dimensional, Navier Stokes – Internal and external situations – Dispersed Multiphase (DMP) is a better model of the cloud than LMP and is computationally fast – Mesh morphing and/or remeshing for large ice shapes – Increased productivity and less prone to errors • Single tool, model, and process for internal/external flows, CHT, collection efficiency and ice accretion One Tool. One Model. One Process.
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