Activity: Laminar vs. Turbulent Flow Around
an Object
Steve Oden, Educator
MathScience Innovation Center
Developed with funding from the MathScience Innovation Center
Major
Understanding
Who has an easier time swimming: a whale or a water flea? As water flows
across and around an object, it does so in definable patterns. Laminar flow,
characterized by smooth motion adherent to the object, occurs when the object
is small or the flow is very slow. Turbulent flow, characterized by chaotic and
rough motion around the object, occurs when the object is large or the flow is
rapid. In this activity, students use a soda straw moved through rheoscopic fluid
to view the effects of object speed on the type of flow generated.
Materials
For each student or team of students:
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1 Small plastic containers (about 24cm long)
Tap water
1 standard sized soda straw
Rheoscopic fluid, colored
Safety
There are no special safety concerns with this activity.
Directions
1. Add several drops of food coloring to the rheoscopic fluid. Red, blue, or
green are the most visible.
2. Add tap water to the plastic container to a depth of about 1 inch.
3. Add 3 or 4 drops of rheoscopic fluid to the center of the container. It is best
to hold the dropper very close to the surface of the water to minimize
mixing of the fluid into the water.
4. Hold the straw vertically (like you would if you were going to drink the
water) to one side of the rheoscopic fluid you just added. Carefully and
slowly move the straw through the middle of the rheoscopic fluid and
observe the motion of the fluid around the straw. Does it seem to cling to
the sides of the straw and swirl away from it? Does the fluid follow the
straw in a smooth and straight pattern or does it create eddies that spiral
away from it? Draw the pattern the fluid creates.
Laminar vs. Turbulent Flow Around and Object
http://MathInScience.info
© MathScience Innovation Center, 2011
5. Add another drop of rheoscopic fluid and repeat step 4, this time moving
the straw rapidly through the fluid. Contrast the patterns created with those
resulting from the slow passage of the straw. Draw the pattern the fluid
creates.
6. The slow movement of the straw created laminar flow, which is very
smooth and tends to “stick” to the sides of the straw. The rapid movement
of the straw created chaotic turbulent flow.
7. Predict how the flow would differ between straws of different diameters
moved at the same moderate speed. Which would yield laminar flow and
which would yield turbulent flow?
Optional
Procedures
Experiment with different objects and different sized straws. How does the
design of the object affect the type of flow?
Additional
Resources
Review lessons and tutorials on nanoscience at www.MathInScience.info.
Analysis
1. Describe or draw the flow of water around your straw when you move it:
A. Slowly
B. Rapidly
2. Which flow is laminar and which is turbulent?
3. Based upon this activity, what seems to be the determining factor of
whether flow is laminar or turbulent?
4. What other factors might change the type of flow?
5. Which type of flow do you think a blue whale creates? A microscopic
animal?
6. Which type of flow do you think is more conducive to swimming? Why?
Laminar vs. Turbulent Flow Around and Object
http://MathInScience.info
© MathScience Innovation Center, 2011