Truck Aerodynamic Improvement using CFD

Truck Aerodynamic Improvement using CFD

ME 491 ProjectDepartment of Mechanical Engineering, IUPUIJulia Zafian-ShortDecember 2004

2 Julia Zafian-Short12/2004

Outline

• Goals and Approach

• Computational Setup

• Results

• Design Improvements

• Summary and Conclusions


Goals and Approach

• To quickly improve truck aerodynamics.

• Apply 2-D CFD using Star-design.

• Quantitative post processing using starviz.


Computational Setup

• Domain and boundary conditions

• Mesh

– Parameters

– Cell type and sizes (near wall and far field)

• Solver parameters

– Equations

– Differencing scheme

– Convergence criteria


Domain and boundary conditions

Inlet (30m/s)

Pressure (0 Pa gage)

Pressure (0 Pa gage)

Slip Wall


Mesh

Default Star-Design Settings

Tetrahedral cells in far field with prism around walls


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


Results

• Velocity

• Pressure

• Streamlines


Velocity0-50 m/s, Increment 5

RecirculationHigh Velocity Gradient

Non-Uniform At Boundary


Pressure99,000-101,500 Pa, Increment 2500


Streamlines


Design Improvements

• Geometry modifications

• Computational results

– Velocity

– Pressure

• Drag comparison


Modified Truck Velocity


Modified Truck Pressure


Streamlines for Modified Truck

Reduced Wake


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%

Truck Aerodynamic Improvement using CFD

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