Kaye Effect Shampoo Jet Rebound Science Project

ISEF Category: Physics and Astronomy

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

The Hook

A thin stream of shampoo can do something that looks wrong. Instead of splashing, it can skate across its own pool and bounce away like a tiny fluid bridge. That odd rebound, called the Kaye effect, hides a real mechanics problem you can measure. Your job is to find when the bounce starts, and predict it with data.

What Is It?

The Kaye effect happens when a shear-thinning liquid, like shampoo or liquid soap, gets blasted into its own pool. Shear-thinning means the liquid gets thinner, or less viscous, when it moves fast. Think of it like honey that suddenly acts more like water when you stir it hard enough.

When the jet hits the pool, the moving liquid near the impact zone can form a slick layer with much lower resistance. That layer can let the incoming stream ride on top instead of merging right away. If the flow conditions are just right, the jet rebounds at an angle and travels across the surface for a short distance. You can study the height where this starts, then compare your measurements with a fluid model in OpenFOAM.

Why This Is a Good Topic

This makes a strong science fair topic because you can vary one clean input, the jet height, and watch for a clear yes-or-no outcome, rebound or no rebound. The project connects to fluid mechanics, consumer products, and industrial pumping of non-Newtonian liquids. You can learn how to collect high-speed video data, define a threshold, fit a rheology model, and compare experiment with simulation.

Research Questions

• How does jet height affect the onset of rebound in a shampoo stream?
• What is the effect of nozzle diameter on the critical height for the Kaye effect?
• Does changing shampoo concentration with water shift the rebound threshold?
• To what extent does the impact angle change the rebound distance after onset?
• Which viscosity model fits the observed rebound threshold best, a constant-viscosity model or a Carreau-Yasuda model?
• How does the measured critical height compare with OpenFOAM predictions across different flow rates?

Basic Materials

• Smartphone with 240-fps video mode.
• Tripod or stable phone stand.
• Washable shampoo or liquid soap.
• Water for dilution trials.
• Small funnels or interchangeable nozzles.
• Ruler or meter stick for scale in video frames.
• Clear shallow tray or basin.
• Graduated cylinder or measuring cup.
• Digital kitchen scale for preparing mixtures.
• Notebook or spreadsheet for data logging.
• Strong side light or LED lamp for video contrast.

Advanced Materials

• University rheometer for measuring shear-thinning parameters.
• Access to OpenFOAM on a capable computer.
• High-speed camera with calibrated optics.
• Precision syringe pump or peristaltic pump.
• Multiple nozzles with known inner diameters.
• Surface tension meter, if available.
• Temperature probe for fluid control.
• Image calibration target.
• Particle tracking or dye for flow visualization.
• Computing access for mesh refinement and parameter sweeps.

Software & Tools

• OpenFOAM: Simulates the flow field and tests how the rebound threshold changes with rheology parameters.
• ImageJ: Measures jet height, rebound angle, and frame-by-frame motion from video.
• Tracker: Extracts position and velocity data from high-speed footage.
• Python: Fits curves, runs statistics, and compares experiments with model output.
• Google Sheets: Organizes trials, codes outcomes, and makes quick plots.

Experiment Steps

1. Define the exact rebound event you will count as onset, so your threshold is repeatable.
2. Choose one main variable to change first, such as jet height, while holding flow rate, nozzle size, and fluid mix steady.
3. Plan a video setup with fixed lighting and a visible scale, so each frame can be measured the same way.
4. Build a calibration plan that links camera measurements to real distances and lets you mark the critical height.
5. Fit your fluid to a shear-thinning model, then decide which parameters you will import into OpenFOAM.
6. Design a comparison between measured onset and simulated onset, then decide how you will report error and uncertainty.

Common Pitfalls

• Changing room light between trials, which makes the rebound edge hard to detect in video frames.
• Using a shampoo mix that separates over time, which changes viscosity during the session.
• Measuring jet height from the wrong reference point, which shifts the critical value by a lot.
• Treating every splash as a rebound, which inflates false positives.
• Ignoring nozzle wear or clogging, which changes flow rate without warning.

What Makes This Competitive

A class-level project usually stops at, the jet bounced or it did not. A stronger project defines a clear threshold, measures uncertainty, and tests more than one fluid condition. You can raise the level by comparing experiment to a rheology-based simulation, not just a simple trend line. Careful control of nozzle geometry, flow rate, and viscosity model will matter more than flashy visuals.

Project Variations

• Test different brands of shampoo, then compare how surfactant formula changes the rebound threshold.
• Swap in liquid hand soap or dish soap to see whether the same shear-thinning pattern appears.
• Analyze rebound distance and rebound angle, not just onset height, to build a fuller mechanics model.

Learn More

• PubMed: Search review articles on shear-thinning fluids, non-Newtonian flow, and rheology terms linked to the Kaye effect.
• NASA NTRS: Search for fluid mechanics reports on jet breakup, surface impact, and flow instabilities.
• MIT OpenCourseWare: Look for fluid mechanics lecture notes that cover viscosity, shear stress, and non-Newtonian fluids.
• OpenFOAM User Guide: Read the free documentation to learn how to set up multiphase or viscous flow simulations.
• Journal of Non-Newtonian Fluid Mechanics: Search the journal for papers on the Kaye effect and shear-thinning jet rebound.