Truck Aerodynamic Improvement using CFD

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Truck Aerodynamic Improvement using CFD

• ME 491 Project
• Department of Mechanical Engineering, IUPUI
• Julia Zafian-Short
• December 2004

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Outline

• Goals and Approach
• Computational Setup
• Results
• Design Improvements
• Summary and Conclusions

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Goals and Approach

• To quickly improve truck aerodynamics.
• Apply 2-D CFD using Star-design.
• Quantitative post processing using starviz.

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Computational Setup

• Domain and boundary conditions
• Mesh
• Parameters
• Cell type and sizes (near wall and far field)
• Solver parameters
• Equations
• Differencing scheme
• Convergence criteria

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Domain and boundary conditions
Pressure (0 Pa gage)
Pressure (0 Pa gage)
Inlet (30m/s)
Slip Wall
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Mesh
Default Star-Design Settings
Tetrahedral cells in far field with prism around
walls
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Solver Parameters

• Assume Incompressible air for flow field
• Solve Momentum Equations
• Solve Continuity Equation
• Using k-epsilon turbulence model
• Convergence Criterion, 0.001 Mass Residual
• Using Upwind Differencing Discretization

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Results

• Velocity
• Pressure
• Streamlines

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Velocity0-50 m/s, Increment 5
Non-Uniform At Boundary
High Velocity Gradient
Recirculation
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Pressure99,000-101,500 Pa, Increment 2500
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Streamlines
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Design Improvements

• Geometry modifications
• Computational results
• Velocity
• Pressure
• Drag comparison

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Modified Truck Velocity
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Modified Truck Pressure
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Streamlines for Modified Truck
Reduced Wake
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Summary and Conclusions

• There may be some error due to the cells being
  large in high gradient regions.
• There may be some problems due to upwind
  differencing.
• Drag produced on the 2D truck is 8212.56 N for a
  2m wide truck, with 0.15 flow error.
• Drag produced on the modified is 4767.52 N for a
  2m wide truck, with 0.3 flow error.
• The modifications reduce the drag by about 42