In this post, I want to outline an activity I do with students to demonstrate a method for finding research questions that are both doable at school or in one's basement as well as original questions where one may make a new discovery. It involves a phenomenon all of us encounter every day, since we all use sinks, bathtubs, and drinking fountains every day - the hydraulic jump. This is when a stream of water falls on a hard surface, spreads out smoothly (laminar flow) and at some radius the water flow rises up and becomes turbulent...this is the jump.
Now, it is true that the hydraulic jump has been known to exist and studied in the lab for over a century. How can we possibly find out something new? We can by thinking about every conceivable physical parameter that might have some effect, big or small, on the nature of the jump. This involves picking apart something that at a glance and without any thinking, seems utterly simple. Here, water flows out, then jumps. What's so special about this?
The activity (go to the link, click on The Science Teacher: Hydraulic Jump... article) is simple for students. I have a beaker of water, some type of hard plate sitting on top of a block in the middle of a tray or pan, which is used to collect the water you are about to spill on the plate, and that's it. Students pour the water so the stream hits the plate at a right angle, and I literally tell students to play with the system, with a goal of thinking of at least 10 things that might possibly affect the size or shape of the jump they observe. Within 5 minutes, students tend to have more than 10 possible parameters!
A list might look like this (highlighted ones are linked to papers students have done):
height the water falls from
the diameter of the stream of water falling towards the plate
temperature of the water
whether the stream is falling smoothly (laminar) or has turbulence/is winding/vibrating
the flow rate of the water
the material the plate/surface is made from
whether the plate is flat or angled
whether the plate is still or moving side to side
whether the plate is still or moving up and down (frequency and amplitude combinations)
whether the plate is moving on a see saw
temperature of the plate
if the plate is smooth or rough
if there are engraved lines/patterns of any kind on the surface (could be numerous patterns tried, which may be symmetric or asymmetric, any of which may not have been tested in prior experiments; these could have ranges of depth in the surface, and so on)
the viscosity of the fluid (what if one used syrup instead of water?)
if there are multiple streams hitting the surface (i.e. jumps interact)
does gravity matter? Would a jump form on the moon?
the angle the stream hits the surface
environmental factors: air pressure, air temperature, humidity in the air, any wind
if the plate is rotating
structure of the stream as it hits the surface
combinations of any of these parameters/situations
Right there, within minutes, students may have dozens of possible experiments to try on something that does NOT require fancy equipment or a professional lab; just a little creativity and elbow grease from a teacher and/or student who puts the experiment(s) together. If one looks in journals for mathematical models of hydraulic jump, they will focus on flow rate, viscosity, and height above the surface from which the stream falls, and that is about it.
For those that have links to papers, the papers have pictures and more detailed outlines of the apparatus students built and used, and how they went about obtaining data for these studies. Use these old papers as guides to design and build your own apparatus and experimental procedures!
Try using this method on any everyday phenomenon with which you are curious! Play with it in a controlled way, and make a list of any and all parameters that even might make any difference in the phenomenon. With some literature searches, using Google Scholar or any university database (which we can help with), you can determine if thorough and serious work has been done on the question(s) you have in mind.
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