Truck Aerodynamic Improvement using CFD

ME 491 ProjectDepartment of Mechanical Engineering, IUPUIJulia Zafian-ShortDecember 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

Inlet (30m/s)

Pressure (0 Pa gage)

Pressure (0 Pa gage)

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

RecirculationHigh Velocity Gradient

Non-Uniform At Boundary

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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%