Wind Tunnel Presentation
Transcript of Wind Tunnel Presentation
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Wind Tunnel Aerodynamics 2016
Erika Clifford, Evan Lerner, Garrett Cook, Katie Megerian, Max Kang, Rebecca Martin, and William Aherne
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Overview● Introduction● Models● Preparation● Experiment 1:
Pressure Measurements ● Modifications● Experiment 2: Wake Measurements● Experiment 3: Flow Visualization● Conclusion
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IntroductionPurpose
To carry out experiments on scaled down automobile models in order to determine and analyze aerodynamic characteristics
Tasks
● Model Preparation● Wind Tunnel Set-up● Different Measuring Techniques
○ Pressure○ Force○ Flow Visualization
● Improvement of Aerodynamic Behavior3
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Recurring Terms● Static Pressure: experienced by a fluid particle as it moves near a surface.
● Stagnation Pressure: experienced when a flowing fluid decelerates to zero velocity without friction.
● Dynamic Pressure: difference in the stagnation and static pressure.
● Freestream: uninterrupted air flow towards the model
● Drag Coefficient: dimensionless value demonstrating strength of drag force
● Wake: area of turbulent flow behind the car
● Boundary Layer: attaches air-flow to car. When this separates off the car, drag is created
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Models 1:18 Scale (Pictures)
Porsche Panamera Turbo Ford Mustang Lamborghini Gallardo
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Model Preparation ● Determine x- and y-positions of pressure taps● Drill pressure taps on top and bottom of model● Connect metal tubes using superglue and epoxy● Smooth hole surface using filler● Connect small plastic tubes to metal pipes for pressure measurement
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Air flow
Y
X
P∞
Prandtl tube
Capacitance Manometer
Difference in static pressures
Experiment 1: Pressure Measuring
Resistance Thermometer(pt-100)
Temperature measurement
P∞Pi
* Please refer to each car’s poster for individual graphs and data
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Modifications to Reduce Drag Porsche:● Tape windows closed● Cover windshield and
hood grooves with clay
Mustang:● Taped windows closed● Hood edges rounded● Grooves filled in● Back end rounded
Gallardo:● Rear extension● Addition of clay● Wheels and windows
covered
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Experiment 2: Wake Measuring
* Please refer to each car’s poster for individual graphs and data9
Air flow
YX
Capacitance Manometer
PtP∞
Prandtl tube
Capacitance Manometer
P(y)
0 (cm) 48 70 81.5
Difference in static pressures
Dynamic pressure in wake
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Comparing Velocity Profiles
10Velocities Scaled
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Experiment 3: Flow VisualizationThree videos were taken of smoke streaklines along the axis of models at airspeeds of 1 m/s, 1.4 m/s and 2.5 m/s for both the modified and unmodified cars. ● Modifications delayed boundary layer separation● Wake size was reduced and as a result so was drag
Original Model Modified Model 11
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Reduction in size of wake
Unmodified Modified12
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Conclusions● Experiment 1 provided an accurate estimation for points of flow separation
● Experiment 2 verified that changing geometry affects drag
● Experiment 3 created a visual representation of the difference in flow
separation between the modified model and the original model
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Questions?
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