Spoiler cfd updates
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Spoiler CFD - Updates. Reviewed By Jaiganesh. Santosh M&S CoE, EIEC, Pune 23 rd June 2011. Objective & CFD Model. Objective: To perform mesh sensitivity study at low velocity To predict drag at different velocities (20 - 50m/s). Taurus. Model set up Wind Tunnel Testing.

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Spoiler CFD - Updates

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Spoiler cfd updates

Spoiler CFD - Updates

Reviewed By

Jaiganesh

Santosh

M&S CoE, EIEC, Pune

23rd June 2011


Objective cfd model

Objective & CFD Model

  • Objective:

  • To perform mesh sensitivity study at low velocity

  • To predict drag at different velocities (20 - 50m/s)

Taurus

Model set up Wind Tunnel Testing

CAD Model used in CFD

Taurus model is used to leverage developed CFD methodology on actual car


Spoiler cfd updates

CFD Domain

Actual CFD Domain

Boundary Conditions

Extended CFD Domain

Working fluid : Air @ std atmospheric conditions

L

Outlet

Inlet

2L

5L

Inlet is placed 2L distance from the leading edge & Outlet is placed at 5L distance from trailing edge of Car in order to capture wake effects properly


Spoiler cfd updates

Results

Mesh sensitivity Study

Drag Prediction at Different velocities

After 7M error is < 5%. 7M mesh is finalized for

drag prediction of car model without spoiler.

CFD results are > 95% agreement with test data


Spoiler cfd updates

Velocity Vectors

20m/s

40m/s

At high velocity more separation observed


Spoiler cfd updates

Test and CFD Comparison

  • Variation in test and CFD is < 0.5 N for entire velocity range

  • Absolute error at low velocity is more as force values at low velocity is less

  • Possible Reasons for Drag variation at low Velocity:

  • At low velocity Re is low compared to high velocity. Simulation is carried out by using high turbulence model (k-ω). These turbulence model gives very good results when flow is fully turbulent. At low velocity flow is more viscous near to wall compared to high velocity flow

  • It is necessary that turbulence specification (turbulent intensity and turbulent length scale) should be appropriate at the boundary while solving CFD (it is recommended that these specification should be come from wind tunnel test)


Spoiler cfd updates

Summary

  • 7M mesh is finalized for further studies for car without spoiler

  • CFD results for drag force over car model without spoiler are > 95% agreement with test data

  • Key learning: Perform mesh sensitivity at low velocity & Finalize the mesh size for further analysis


Spoiler cfd updates

Next - Plan

  • Required :

  • Test procedure of drag calculation (with picture) and Information about the test calibration curve (How it is generated)

  • Test data with Repeatability & Reproducibility

  • Difference between measuring instrument used for Ahmed body and Car model

  • Information about measurement gauge (accuracy and calibration)


Spoiler cfd updates

Total Pressure contours

20m/s

40m/s


Spoiler cfd updates

Static Pressure contours

20m/s

40m/s


Spoiler cfd updates

Velocity contours

20m/s

40m/s


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