Other fluids education resources IV: Science puzzles and fluids lab books

I have been looking around for more demonstrations to use in class and have assembled a list of various books that either directly describe in class activities (or out of class labs) and others that are focused on younger audiences but that can be adapted to demonstrate various fluids phenomena. Some I have described in prior posts but I will aggregate all the books I have come across here. Over the next few months I will be writing up some ideas from all but the first book listed.

H2OH! has an extensive list of in class demonstrations complete with parts lists and descriptions of how to run the activity. The book was assembled by the American Society of Civil Engineers a few years ago so it leans toward civil engineering applications in certain areas. There are a lot of ideas in this book. The only downside is that some of the physical and mathematical explanations are not as rigorous as they could be.

Experiments in Fluid Mechanics (edited by Robert Granger, out of print) contains over 60 experiments that cover fluid properties, hydrostatics, kinematics, dynamics and even acoustics. In general the experiments would be hard to do in class and many of them are now (commercially available) standard teaching laboratory experiments. However, some can be adapted to a class room setting and in all cases the theory and explanations are good.

Professor Povey’s Perplexing Problems: Pre-university Physics and Maths Puzzles with Solutions is mainly focused on physics and math mental problems and apparent paradoxes (such as the Stevin paradox in hydrostatics). The problems are well described though the explanations are sometimes a little wordy. There quite a few hydrostatics problems in the book that I think could really force students to understand the material. They are many of them that easily lend themselves to being demonstrated in class (such as a Galileo balance).

Martin Gardner’s Science Magic: Tricks and Puzzles is mainly focused on using various physical phenomena as ‘magic tricks’. The tricks are simple though there is little in the way of detailed physical explanations. It is not just limited to fluid mechanics so the tricks could be used for a range of undergraduate science classes.

Entertaining Science Experiments with Everyday Objects is another book by Martin Gardner. It is pitched at the same level as their Science Magic book and there is some overlap. Both are worth getting out of the library (or buying, they are not expensive).

Build a Rocket Boat and 18 More Wild Wind Projects (Science Dares You) is aimed at parents of children aged 4-8 so the physical explanations are essentially useless at a college level. However, there are some very simple ideas that illustrate various phenomena. For example, this book had the easiest method for making a Cartesian diver that I have found (see my write up here).

An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

Take home lab experiment – flow rate from a hose

I typically use this lab as the 3rd or 4th lab of the semester. The lab is simple enough, they have to use two different methods to measure the flow rate out of a hose. They can use kinematics, conservation of volume, or even momentum (though this is a little more tricky). This is one of the labs where I ask my students to use their estimates of measurement uncertainty, through some basic linear error analysis, to estimate their calculated flow rate uncertainty. If their 2 measurements are not the same (within the bounds of uncertainty they calculated) they have to discuss why not. It is a great experiment for discussing errors because, even though the measurements are simple to make, they often have significant percentage errors that propagate into very large percentage error in their calculated flow rates. For example, measuring the diameter of the hose outlet can be tricky and a 10% error in the measurement becomes a 20% error in the hose area. There are also challenges with repeatability of the experiments as it is hard to get the hose to have the same flow rate each time you turn it on. I do not explicitly ask them to discuss repeatability but rather I discuss it when I return the graded reports and ask them to think about repeatability as part of their next take home lab.

As with all the take home labs I will not publish methods for conducting the tests as I still use them in class and want my students to figure it out on their own.


Introduction

In this class we have looked at a range of different flow analysis techniques (conservation of mass, kinematics, Bernoulli, momentum, etc.). In this 3rd lab you need to use 2 different approaches to calculate the flow rate from a garden hose.

Task

  1. Run a series of experiments to establish the flow rate our of the flow from a regular garden hose. There is a hose in the fluids lab that you could use. You can use buckets, measuring tapes, and stopwatches. If you wish to use anything other than that you will need to check with me first. You are not to use laboratory flow rate measurement devices such as the venturi meter.
  2. Write a brief report (3 page max) that:
    1. Includes photos of you running your 2 experiments.
    2. Describes how the test was run
    3. Includes diagrams showing what you measured
    4. Presents the theory and equations you used in your calculations
    5. Lists what data was collected and estimates of your measurement error (in a table)
    6. Error analysis (see class notes) to estimate your uncertainty in your calculation of flow rate.
    7. A table listing the two calculated flow rates and your uncertainty estimation.
    8. If the two measurements to not agree (within the error range you calculated) then discuss why not.

Due date in 2 weeks


An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

Take home lab – Relative viscosity

I have been trying to think about how to have students measure the viscosity of a fluid in their kitchen. The problem is that you need to make a lot of measurements (not least of which is the fluid layer thickness) that are (1) hard to make and (2) have potentially very large error. However, if the errors are consistent then it should be possible to quantitatively compare the viscosity of two different fluids using the identical test. I think that this may be a way around the problem.

The instructions given below are for one of the first take home labs that I use in a semester. The goal is to find the ratio of the viscosity of two common fluids you can find in a kitchen. There are a number of possible ways to approach this problem as long as you are not too hung up on accuracy beyond order of magnitude. At this stage in the semester the students have been down to the lab to measure the viscosity of a range of fluids including oil, molasses, corn syrup so they have data they can use for comparison. It is also possible to look up a lot of viscosity values at http://en.wikipedia.org/wiki/Viscosity.

The first time I ran this lab I got a range of results. It was the first lab of the semester and so the students were a little unsure how to approach the write up. However, the range of experiments they ran were very impressive. One team even built a simple viscometer using a cup, some string, a pencil, and a pile of pennies. I also had students researching online how to measure viscosity. That was all great. The actual quantitative results were less great. It is actually very hard to do well. It is also hard to get a simple theoretical model for some of the tests they ran. For example, you can place equal volumes of different fluids at the top of a slope and time how long each takes to travel a certain distance. However, the time taken is a function of the  fluid density, the thickness of the slug of fluid flowing down the slope, and the viscosity of the fluid. It is, therefore, hard to control for all these parameters in order to get a viscosity ratio. There was also the age old problem of students not actually reading the instructions and instead of a viscosity ratio giving estimates of the actual viscosity which were obviously way off. I also had students picking non-Newtonian fluids which complicates things a little. In future I may move this lab to later in the semester.

As with all the take home lab write ups I will not publish detailed methods for conducting the tests. I still use them in class and want my students to figure it out on their own.


Instructions to students

On your first visit to the fluids lab you used a viscometer to measure the viscosity of various fluids. In this take home lab you will need to calculate the ratio of the viscosity of 2 common household fluids such as oil, honey, syrup, or molasses. Ideally you would use fluids that you also used in the viscosity lab.

Task

  1. Identify 2 fluids that you will be using to measure viscosity.
  2. Run a series of experiments to establish the ratio of the viscosity of the two fluids you selected. That is, develop an experiment that will allow you to compare the two fluids viscosity’s without necessarily accurately measuring the viscosity of the individual fluids.
  3. Write a brief report that
    1. Is 3 pages max including photos of you running your experiments
    2. Details how you made the measurements including clear diagrams showing your setup
    3. Details of how you used the measurements to calculate the viscosity ratio (include any appropriate free body diagrams)
    4. Compares your measured ratio to that based on tabulated data from textbooks or online (or you can use your results from the first lab).
    5. Quantifies potential sources of error that explains any discrepancy between your measurements and your lab or tabulated data.

Rules

  1. You may not use equipment in the fluids lab or any other scientific lab equipment
  2. You should only use items that are commonly available in your home.
  3. If you need to go to a store to buy something please come and see me first. I may be able to lend you something or I will buy it and then lend it to you. You will need to explain why you need it and it should be cheap.

Due in 2 weeks


An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

Take Home Lab – Measuring the mass flow rate from a compressed air can

The mass flow rate of a fluid appears many times in an introductory fluids class (pump power, conservation of mass, momentum, etc.). This take home lab requires students to use at least two different approaches to measure the mass flow rate out of a compressed air can. My experience with this is that some students struggle with finding a second way to do the measurement. This has led to some rather creative, if not physically appropriate, measurement methods.

It is a nice experiment because there are substantial difficulties in taking accurate measurements. For example, it is hard to accurately measure the diameter of the straw connected to the can as it is so small. It is not unusual to have a measurement uncertainty of 50-100% in the diameter leading to an error/uncertainty of up to 400% for the straw area. These errors  can make a substantial difference to the resulting calculated mass flux. There can, therefore, be substantial differences between the two sets of measurements that are still within the bounds of uncertainty. There is also a repeatability problem with this lab that is easily observed and explained if one is paying attention to the data.

air can

As with other take home labs that I use later in the semester, the students are required to do some basic error analysis to explain the differences between their two measurements. This is a very useful complement to their fluids lab class that runs in parallel with the main lecture class. The students need to estimate the uncertainty in each measurement they take and then use that data to estimate the uncertainty in their measured mass flow rate.

As with all the take home labs I will not publish details on specific methods for conducting the tests as I still use them in class and want my students to figure it out on their own.


Instructions to students

Introduction

 In this class we have looked at a range of different flow analysis techniques. In this lab you need to use 2 different approaches to estimate the mass flow rate coming out of a compressed air can such as are used for cleaning computer keyboards.

Task

  1. Run a series of experiments to establish the mass flow rate out of a compressed air can. You can borrow an air can from me when you are ready to do your testing. You may use an electronic scale and a stopwatch but otherwise only non-lab equipment is to be used without permission. If you would like to use something else you need to check with me.
  2. Write a brief report that
    1. Is a maximum of 3 pages including photos of you running your experiments.
    2. Describes the experiment(s) you used to establish your result including
      1. How the test was run
      2. What data you collected including estimates of your measurement uncertainty
      3. How you performed your calculations including diagrams (with control volumes), equations, and relevant theory
      4. A quantitative discussion of the uncertainties in your measurements and calculations including an analysis of the differences between your two sets of measurements.

Due in 2 weeks


An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.

Take home lab experiment – Ranking of common fluids by density

This is a very simple take home lab to get students started into the semester. They are asked to use three different techniques to rank a range of common fluids (that can be found in one’s home) by their density . There are a broad range of approaches to this including directly measuring their density, using buoyancy, using multi-fluid manometers, or simply stacking them up. However, there are also some tricks to this as well. For example, it is easy to end up with two or more of the fluids being miscible making it hard to float one on the other. It is also a great introduction to quantifying errors. Many common fluids are quite close in density so often the student groups would get different rankings from their different experiments. This illustrates that even simple measurements have error/uncertainty associated with them. This provides a great motivation for discussing measurement errors and resulting calculation uncertainty (though at the start of the semester I typically only discuss measurement error and move onto error analysis later).

As with all the take home lab write ups I will not publish detailed methods for conducting the tests. I still use them in class and want my students to figure it out on their own. The instructions I give to students are below.


 Introduction

As we have seen in class different fluids have different densities. Density is a fluid property that varies with temperature (and pressure but not very much). Accurately measuring the density of a given fluid can be done in many ways and you are welcome to research this as part of this assignment.

Task

  1. Identify 5 common fluids that you find in everyday life (kitchens are a good place to start)
  2. Run a series of experiments to establish their relative densities (that is, rank them by their density)
  3. Use three different experimental techniques to establish this ranking.
  4. Write a brief report that
    1. Is 2 pages max including photos of you running your experiments
    2. Describes the experiments you used to establish your rankings
    3. Includes a table of fluids ranked by density

Rules

  1. You may not use equipment in the fluids lab or any other scientific lab equipment
  2. You should only use items that are commonly available in your home
  3. If you need to go to a store to buy something please come and see me first. I may be able to lend you something or I will buy it and then lend it to you. You will need to explain why you need it and it should be cheap.

Due in 2 weeks


 

An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.