Aircraft Icing: Computational Studies Team

1
Aircraft Icing Computational Studies Team

• ASE-463 Q
• Fall 2006
• Advisor
• Dr. Graham F. Carey
• Members
• Vikram Garg
• Cuong Tran

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Presentation Outline

• Background and Motivation - Cuong
• Finite Element Method - Vikram
• Meshing - Cuong
• Post-processing and Preliminary Results - Vikram
• Completed and Future Work - Cuong

3
Background

• Icing on wings rapidly frozen water droplets
  accumulate on wings
• Negative effects loss in lift, increase in
  drag, lower stall angle, and loss of stability
• Cessna wingtips subject of study in our
  department

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Motivation

• Experimental approach
• limited choice of parameters
• time-consuming
• Numerical approach
• input parameters easily modified
• data extraction is simple and robust
• fast design modifications are possible for
  optimization

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Objectives

• To model the effects of icing on the flow field
  around an airfoil
• Formulate and implement a Finite Element solution
  of the mathematical model
• Extract appropriate data from the simulations to
  compute performance parameters (CL, CD, etc)
• Analyze the impact of the icing on aircraft
  stability (CM)

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Finite Element Method

• Numerical method to solve flow PDEs.
• Discretize domain meshing
• Introduce approximations to variables
• Solve a (or a sequence of) linear system(s) to
  get approximate solution

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Governing Equations

• Basic equations governing incompressible, viscous
  (Newtonian) fluid flow
• Re Reynolds number - different flow regimes
• 0 lt Re lt 10 Stokes flow
  
• 10 lt Re lt 1000 Laminar flow
• 1000 lt Re ... Turbulent
  flow

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Solution Methodology

• First get a mesh (Unstructured, Triangles)
  Matlab TRIANGLE
• Formulation Weak form, add numerical
  stabilization term
• Assemble and solve linear system (or seq.) to get
  - Libmesh
• Prelim. Post-process P distribution, vel.
  profiles

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Airfoil Specs

• Swept GLC-305 airfoil
• 18.72 inch chord length
• Chord length used for non-dimensionalization (Re,
  L, etc.)

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Meshing

• Wrote Matlab code to extract x y coordinates of
  each airfoil
• TRIANGLE uses nodal points along airfoil
  bounding box to create a mesh
• Libmesh uses triangular elements
• Linear (with 3 nodal pts) for pressure
• Quadratic (with 6 nodal pts) for velocity

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Meshing Results
TRIANGLE meshing output
Clean Airfoil
Zoomed in on Ice Horn
The fine, detailed meshing near the surface of
each airfoil enables accurate data acquisition.
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Pressure Distribution

• Re 100, steady state
• Distortion at leading edge due to ice, flow
  attached in rear for both cases

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Pressure Distribution

• Re 1000, s-s
• Similar to Re 100

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Velocity Profile
Re 1000, boundary layer growth, s-s
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Unsteady Flow

• Re 100, pressure disturbance due to ice horn
• Ice effects significant, but again localized

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Separation

• Icing small separation bubble, Re 100

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Completed Work

• Numerical simulation meshing, solving
• Finite Element formulation of NS equations
• High Reynolds No. - with numerical stabilization
• Code Validation Backwards Facing Step

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Future Work

• Currently working on unsteady stabilized
  simulations for higher Re numbers
• Write routines for CL, CD, CM
• Stability analysis from simulation data

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Questions

• Do you have any?