experimental wake investigation of a solar powered car4 with pic for final pres

8/6/2019 Experimental Wake Investigation of a Solar Powered Car4 With Pic for Final Pres

1/19

EXPERIMENTAL COEFFICIENT OF

DRAG DETERMINATION FOR A

SOLAR-POWERED VEHICLE

Lab Group 4

ASE 120K Fall 2009


2/19

Introduction

University of Texas entry in North

American Solar Challenge

Determine the coefficient of drag Test at various Reynolds numbers

ranging from 6x104 and 4.9x105

Will compare results to MIT car from

December 2005 (5)


3/19

Background

1/16th scale

Dynamic similarity off by a factor of 16

MIT Tests (5)

y How were they done?

y What was gained?

y How this affects our study?

Additional studies drawn from AIAAJournal and Journal of WindEngineering


4/19

Background (contd)

Car testing in wind tunnels

y Have to be aware of boundary layer growth

on driving surface

Placing model on raised surface starting very

close to front of model

Other solutions unfeasible

y Formation of wake

Have pitot static tube set up 1 ft behind car


5/19

Apparatus

Closed-circuit subsonic wind tunnel

Model

y

1/16th

scaley 3D printer

y Plate-mounted

Pitot-static tube array

Flow visualization

y Smoke wire (ideally)


6/19

Procedure

Build Modely 3D Printer

y Coat model

Test flat plate alone Mount model on flat plate in wind tunnel

Visualize flow at 10 ft/s increments

Obtain pitot-static tube array datay

2,000 samples per site at 500 Hzy Test Area 4.75 in x 3.5 in

y Test at 1/8 in (~3mm) intervals between sites Forms grid of 1008 points per wind tunnel setting


7/19

Data Evaluation

Use Pitot Static data to create wake

profile at each Reynolds number

y Momentum deficit method

Use flat plate wake height to determine

boundary layer interference on bottom of

the car

Generate a total drag coefficient at eachReynolds number


8/19

Table of contents

Background

Comparison to other works

Apparatus Procedures

Testing

Results Conclusions

Further Research


9/19

Background


10/19

Other relevant tests

Wind tunnel testing of full size vehicles

(Ford, GM, and European wind tunnels)

MIT tests

y How they were done?

y What they found

Reynolds #s

CD calculated


11/19

Apparatus

y Model car

y Flat plate

y Wind tunnel

y Tuftsy Smoke wire

y Pitot rake


12/19

Procedure

Plate testsy Done to insure no turbulent interference from

plate in the test area

Car testsy Finding true test area

y Use of pitot rake

y 10 pitot tubes pressures taken at 53 differentpoints then moved up and done again making20*53 or 1060 points

Flow visualizationy Why done after

y Smoke wire and tufts tests


13/19

Findings

Picture of flow

visualization

y Can either do one

slide for each, smokeand tufts,

y Or do one slide of

both, smoke and tufts

y Bluff bodies of the

wheel wells and thecanopy causes

separation bubbles


14/19

Findings continued

Show final surface graph(s)

y Could show just one and explain how this is

the basic shape

y Or could show all and point out differences


15/19

Results

Reynolds #s Coefficient of Drag

1.587e5 0.00611

2.0489e5 .00396

2.4889e5 .0125

2.9801e5 .0183


16/19

Conclusions

Redesign the solar car if decrease in

drag is desired

Find a way to divert flow from around

the canopy, or keep the flow attached

longer

Drive slower


17/19

Advice for later experiments

Larger model can be used, more

accurate

Keep a close eye on the plate boundary

layer


18/19

Questions?


19/19

References

(1) A. Albers, J. Brys, S. Illg, J. Roop, and J. Ashworth. June 2003. EXPERIMENTALWAKEINVESTIGATION OF IDENTICALCARS IN CLOSE PROXIMITY.American Institute of Aeronauticsand Astronautics.

.

(2) P.W. Bearman. July 1997. Near wake flows behind two- and three dimensional bluff bodies.Journal of Wind Engineering and Industrial Aerodynamics.

.

(3) R. Born. Wind Tunnel Experiment: Mercedes-Benz CLK vs. Duesenberg.All Car Models..

(4) Y. Sakuma and A. Ido. Wind Tunnel Experiments on Reducing Separated Flow Region AroundFront Ends of Vehicles on Meter-Gauge Railway Lines. Japan Science and Technology InformationAggregator.

.

(5) P. Augenbergs. Aerodynamic Optimization of a Solar Powered Race Vehicle. Massachusetts

Institute of Technology. .

(6) Anderson, J.D. (2005) Fundamentals of Aerodynamics. Fourth Edition McGraw Hill, Inc.

(7) Tinney, C.E. (2009) ASE120k Laboratory Handbook. Dept of Aerospace Engineering andEngineering Mechanics at The University of Texas at Austin.

experimental wake investigation of a solar powered car4 with pic for final pres

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