Tabletop Wind Tunnel Airfoil Flow Study

ISEF Category: Physics and Astronomy

Subcategory: Mechanics  ·  Difficulty: Advanced  ·  Setup: School Lab  ·  Time: Full Year

The Hook

A few small bumps can help a wing stay attached to air longer. That sounds backward, but nature uses that trick on humpback whales and owl feathers. You can test the same idea with a tabletop wind tunnel and video-based flow mapping. Your data can show where the air speeds up, slows down, or separates.

What Is It?

This project studies how air moves around different wing shapes. You build a simple wind tunnel, send smoke or haze through it, and record the motion with a phone. Then you use particle image velocimetry, or PIV, which is a way to track tiny moving particles in video and turn their motion into flow speed and direction.

Think of the airflow like a crowd walking past a wall. A smooth airfoil is one route through the crowd. A tubercled or serrated airfoil adds small shape changes that can redirect the flow, keep it attached longer, or change where turbulence starts. You are not just asking which shape looks cooler. You are measuring how the shape changes the air itself.

Why This Is a Good Topic

This is a strong science fair topic because you can change one shape feature at a time and measure a real physical effect. You get a clear engineering problem, which is how shape affects lift, drag, and flow separation. You also get room for real analysis, since PIV gives you velocity fields, not just a yes-or-no result. A motivated student can learn fluid dynamics, image analysis, and experimental design from one project.

Research Questions

• How does the airfoil shape change the size and location of the flow separation region at Re ≈ 10⁴??
• What is the effect of leading-edge tubercles on the local velocity field near the wing surface??
• Does a serrated trailing edge reduce wake width compared with a smooth trailing edge??
• To what extent does angle of attack change the onset of stall for each airfoil design??
• Which bio-inspired airfoil gives the most uniform flow downstream of the wing??
• How does the measured velocity pattern differ between the baseline airfoil and the modified airfoils??

Basic Materials

• Box fan with stable speed setting.
• Cardboard or foam board for tunnel walls.
• Honeycomb straw bundle for flow straightening.
• Clear plastic sheet for viewing window.
• 3D-printed airfoil models with different shapes.
• Smoke source or safe haze source suitable for indoor airflow visualization.
• Smartphone with HD video recording.
• Tripod or rigid phone mount.
• Meter stick or ruler for scale in the video frame.
• Tape, clamps, and hot glue for assembly.
• Marker paper or grid background for alignment.
• Computer with free PIVlab installed.

Advanced Materials

• Access to a 3D printer with fine nozzle settings.
• Laser-cut or machined tunnel inserts for repeatable model mounting.
• Differential pressure sensor for pressure-drop checks.
• Hot-wire anemometer or handheld airflow meter for tunnel calibration.
• High-contrast seeding particles or approved fog generator for cleaner PIV tracking.
• Calibration target for camera scaling and lens correction.
• Data processing computer with ImageJ and PIVlab.
• Optional force balance or load cell for lift and drag estimates.
• Chamber or enclosure to reduce ambient light and stray air currents.

Software & Tools

• PIVlab: Tracks seeded particles between frames and turns video into velocity maps.
• ImageJ: Measures distances, checks image quality, and helps with frame preparation.
• Python: Cleans data, plots results, and compares shapes with simple statistics.
• GeoGebra: Helps sketch airfoil geometry and compare shape changes before printing.
• Google Sheets: Organizes trial data and calculates averages, variation, and error bars.

Experiment Steps

1. Define the one shape feature you will change first, such as tubercle amplitude, serration size, or a smooth control wing.
2. Design the tunnel so the airflow reaches the test section in a repeatable way, then plan how you will check flow uniformity.
3. Set up a camera view that captures the whole region you want to measure and includes a scale reference.
4. Plan the seeding and lighting so the particles or haze show up clearly without washing out the frame.
5. Build a PIV analysis pipeline that converts video into velocity fields and lets you compare trials the same way each time.
6. Decide which metrics will matter most, such as separation length, wake width, or average downstream speed.

Common Pitfalls

• Using a box fan without flow straightening, which leaves swirl and makes the velocity field messy.
• Moving the phone between trials, which breaks scaling and makes PIV comparisons unreliable.
• Choosing airfoil prints with rough surface errors, which can dominate the effect you wanted to measure.
• Overloading the frame with haze, which hides particle motion and ruins frame tracking.
• Comparing shapes at different mounting angles by accident, which makes you measure setup drift instead of geometry.

What Makes This Competitive

A class-level version of this project shows one or two flow maps. A stronger version compares multiple airfoil geometries, quantifies uncertainty, and uses the same imaging pipeline for every trial. You can also earn points by linking flow patterns to a real metric, such as separation length or wake symmetry, instead of only showing pictures. If you add careful calibration and a solid baseline shape, your results will read like engineering research, not a demo.

Project Variations

• Test how a smooth airfoil compares with a tubercled one at several angles of attack, then map where stall starts.
• Compare serrated trailing edges made with different edge sizes to see how wake width changes.
• Replace the airfoil material with flexible prints or thin plastic shells and measure how slight bending changes the flow.

Learn More

• PIVlab documentation: Free particle image velocimetry software guide, available through the official PIVlab project pages.
• NASA Glenn Research Center: Search for beginner-friendly articles on lift, drag, and airfoil flow.
• MIT OpenCourseWare Fluid Mechanics: Free lecture notes and problem sets for basic fluid flow concepts.
• Physics of Fluids: Search the journal for papers on bio-inspired airfoils, tubercles, and serrated trailing edges.
• PubMed: Search for review articles on owl wing aerodynamics and humpback whale tubercle flow effects.
• NOAA educational resources: Search for clear explanations of boundary layers, turbulence, and wind flow.