The article itself is accompanied by a website where we elaborate on our 13 different examples. Check it out, and let us know what you think! And if you have any experiences with co-creating learning that you would like to share, we would love to hear from you and add a guest post on your experiences to our collection! :)
One of my goals as a teacher is to change culture towards responsibility for student learning being shared equally between teachers and students. This is an idea that is met with some resistance, both from students who need to put in more work, and from teachers. An article by Cook-Sather (2014) sheds light on difficulties teachers often experience when letting go of traditional understandings of the relationship between teacher and students, and adopting this new form of collaboration with students:
Taking on a students as partners mindset is described as a threshold concept for teachers: a gateway that, once crossed, opens up a whole new world. While walking through such a portal is transformative and irreversible (evidence of both is given from teacher reflections after they have adopted the new mindset), it is also troublesome. Especially for new teachers who are struggling with legitimacy issues, accepting students as equal partners can be a daunting and difficult process, where students might be perceived as adversaries rather than partners, or as not contributing any new and inspiring thought.
Crossing the threshold might be aided by academic developers inviting for reflection, or by supporting teachers in taking small actions towards giving students more responsibility on a confined and “safe” aspect of the course (note by Mirjam: for some ideas, check out our collection here!). The beginner-level one-on-one setting of teacher and student in partnership (for example working with student representatives) can then, in the long run, be widened to include more students. Providing spaces for reflection, discussion, and revision within and beyond course settings (for example also including educational researchers) can support the transformation towards students as partners.
Reading quotes from teachers struggling to see the benefit of collaborating with students on developing their teaching opened my eyes to struggles with the changing relationship – especially around seeing the student partners as enemies rather than supportive partners — that I did not anticipate for our own application, but that might quite possibly exist. This might be another aspect of threshold concepts – that it is retrospectively difficult to imagine what life was like before crossing the threshold. Therefore, reading this article was a good reminder that supporting reflections on roles, identities, relationships should be an important part of any project if we want to successfully implement students as partners.
Reference:
Alison Cook-Sather (2014) Student-faculty partnership in explorations of
pedagogical practice: a threshold concept in academic development, International Journal for Academic Development, 19:3, 186-198, DOI: 10.1080/1360144X.2013.805694
I love using self-determination theory (Ryan & Deci, 2000) as a framework against which I check all teaching I develop. Is it even possible for students to feel competence, autonomy, relatedness in the environment I am building, or what can I tweak to create conditions in which these contritions for feeling intrinsically motivated are more easily met? Recently, I have taken on a Students as Partners (SaP) approach, and then came across the article by Kaur & Noman (2020) that looks at SaP through the lens of self-determination theory.
The authors take the three categories and divide them into six themes: Autonomy is described as both agency (as having the real chance of contributing and shaping the learning process) and choice; competence is about gaining confidence and thus acting more confidently, as well as being challenged and rising to the challenge. Relatedness is then about both the environment which is inviting and without anxiety, and meaningful, frequent, friendly and open interactions. They say that as a result of the intrinsic motivation that is made possible by meeting these conditions, student engagement will increase.
Looking at the data from two previous studies, the authors find that more than 3/4 of the students reported experiencing agency, which they linked very closely to agency and accountability beliefs of students. 2/3rds of the students also mention choice as very important: they had control of their learning and felt as if they were “the initiators of their learning”. For the category of competence, the results aren’t as strong: less than half of the students reports feeling confident, and less than a third felt challenged. On relatedness, 3/4 of the students report feeling connected and in a warm environment, and almost half of the students felt that they had more meaningful interactions with their teachers.
So what does this mean, and how does it help us? I was most curious about seeing how the authors brought self-determination theory and students as partners together. The numbers themselves are interesting in so far that they tell us something about the two specific courses, but whether or not students feel, for example, appropriately challenged will depend on a lot more factors than on whether or not they are learning as partners, like on the subject, their level of previous knowledge, the actual tasks they are working on, etc.. Just because someone uses students as partners as their framework doesn’t mean that it is implemented perfectly (as with any other framework or method, actually). Also we don’t have anything to compare this to — maybe that’s how students feel about any course, regardless of whether they are partners or not? But I think thinking about self-determination theory in more detail, i.e. what are the different aspects that could contribute to feeling competence, autonomy, and relatedness, and what could help or hinter them, and which of these are more important than others, is useful for improving my teaching practice.
References:
Ryan, R. M., & Deci, E. L. (2000). Self-determination theory and the facilitation of intrinsic motivation, social development, and well-being. American psychologist, 55(1), 68.
Kaur, A., & Noman, M. (2020). Investigating students’ experiences of Students as Partners (SaP) for basic need fulfilment: A self-determination theory perspective. Journal of University Teaching & Learning Practice, 17(1), 8.
I’ve been a fan of working with rubrics for a long time, but somehow I don’t seem to have blogged about it. So here we go!
Rubrics are basically tables of learning outcomes. The rows give different criteria that are to be assessed, and then performance at (typically three) different levels is described. Below, I’ll talk about the benefits that working with rubrics have for both teachers and students, and give two concrete examples of how we used them and why that was helpful.
Rubrics are a great tool for teachers
Designing a rubric makes you really think long and hard about what it is that you want students to be able to demonstrate for the different criteria, and how you would distinguish an ok performance from a good performance for each criterion.
Once the rubric is set up, grading becomes a lot easier. Instead of having to think about how well any given response answers your question, now it’s basically about putting crosses in the relevant cells matching the performance you see in front of you.
This makes it a lot easier when there are many people involved in grading — the dreaded “but x got a point for y and I didn’t!”-discussions become a lot fewer because now grading is a lot more objective
Giving feedback also becomes a lot easier, since all the performance descriptions are already there and it’s now basically about copy&paste (or even sharing the crossed-through rubric) to show “this is where you are at” and “this is what I was expecting”.
It also helps in course planning…
One example of where I was really glad we did have a rubric is the project that Torge and I collaborated on: We bought four cheap setups for rotating tank experiments and designed a course around making otherwise really unintuitive and difficult to observe concepts not only visible, but manipulating them in order to gain a deeper understanding. We had written down a rubric pre-corona, but when we went into lockdown in March 2020, having the rubric helped us a lot in quickly figuring out how to transfer a very much hands-on course online. Since we had clearly identified the learning outcomes, it became very easy to think of alternative ways to teach them virtually. The figure above shows part of the rubric, and circled in red is the only learning outcome in that selection (of a lesson that we thought was all about the hands-on experience!) that wasn’t just as well taught virtually. But looking closely at the rubric, we realised that the students did not actually need to necessarily do the rotating experiments themselves, as long as they were doing some kind of experiment themselves to practice conducting experiments following lab instructions. With the rubric, we had a checklist of “this is what they need to be able to do at the end of class” to directly convert into activities.We ended up with me showing the rotating experiments from my kitchen, while the students were doing non-rotating experiments, using only readily available household items, from their homes. Without the very explicit learning outcomes in our rubric, converting the course would probably been a lot more difficult.
Rubrics are also great for students
They get a comprehensive overview over what the instructor actually expects from them
They can use the rubric to make sure they “tick all the boxes”, or strategically decide where to put their time and effort
Instructor feedback is now a lot more helpful than “2 out of 5 points”.
Kjersti shares an example of how she “negotiated” rubrics in her GEOF105 class to co-create it with her students:
The goal is to invite students to negotiate an assessment rubric for written assignments. We have tested this out in the following way:
The teacher drafted a rubric and assigned an equal weighting of 5 points to each assessment criteria (15 criteria gave a total score of 75 points).
The students voted anonymously for which criteria they wanted to assign a stronger weighting. We made no limits in how many criteria each student could vote for.
The votes were counted up, and the remaining 25 points in the assessment were distributed based on the number of votes for each criterion.
The two criteria most students voted to weight stronger, were the structure of the lab report and the reflection part. I suspect they wanted more points for the structure partly because it is not too difficult, but also because they spend much time figuring out how a lab report should look. I also found it interesting that they wanted more points for reflection. Last year we asked the students to write a reflection paragraph that would not be assessed. We thought it would be stressful for the students to write the reflection knowing it would be evaluated. But, I guess we were wrong!
They also wanted more point for making/discussing hypothesis, using good illustrations and relating the experiment tank to the Earths geometry — all of which are objectively difficult parts of the lab report.
We found two main results after using the negotiated rubric:
The students (on average) achieved higher scores than the previous year (were the rubric was fixed)
The students made fewer complaints to the assignment score
We think the students achieved higher scores because they spent more time getting acquainted with the rubric before writing their assignments and could use it more constructively as a checklist.
So those are our experiences with using rubrics. How about you? We’d love to hear from you!
Participation in shared production of artefacts is a great way to learn in a community, because putting things on paper (or, as we will see later, on online slides or physical whiteboards) requires a clearer articulation of the topic of discussion, and a level of commitment to a shared meaning (Wenger, 1998). We give two examples of methods we like to use, and then a trick to break up roles in student groups so it is not always the same person taking notes or reporting back to the group.
Physical whiteboards
One of Kjersti‘s favourite teaching techniques is the use of whiteboards, especially in GEOF105, a second-year course introduction to oceanography and meteorology (see many examples of great student artefacts on her Twitter; and multiple-choice questions to support discussions as her other favourite method here).
For in-person teaching with group discussions and exercises, the groups can draw or write their main results on portables whiteboards (best trick: Picture frames with just white paper behind the glass! Very cheap, very effective. Great idea, Elin!). When the students are asked to document their results on a whiteboard, they need to be concrete and agree on the level of details they provide.
In our GEOF105 course in undergraduate oceanography, we use many sketching exercises. We find that the sketching exercises provide many positive aspects:
Students like sketching. They often decorate the sketches with smiling suns or add wildlife to the sketches, contributing to a relaxed atmosphere and a positive learning environment.
Many questions arise when the students start sketching, because suddenly having a vague idea is not enough any more. First, they discuss, explain, and check if their ideas make sense. Then, they need to combine all the ideas into one concrete sketch.
The sketching activates more students in the discussions. Some students take responsible for sketching, some provide input, and some ask questions.
Below, you see an example of one group’s work on coastal up- and downwelling on the Northern vs Southern hemisphere (note the use of appropriate animals to illustrate the hemisphere ;-))
Shared online slides
But this type of negotiating of meaning can also happen in a virtual space. We have used shared online slides during group work in both digital and in-person teaching. The slides provide an easy way to provide figures and questions the groups can work on, and you can also add one slide for each group where they write down a summary of their discussion or answers key questions. The sharing of online slides and collaborative writing on them provides several opportunities:
You can keep track of the groups’ progress by looking at their slides. Especially in digital teaching, where you cannot as easily eavesdrop on the students’ discussions, it is difficult to visit all the different breakout groups and get an idea of their progress. Students often dislike it if the teacher jumps into their breakout-group unannounced (ehem, some teachers dislike doing it, too…). We have experienced that students prefer the teacher to pay attention to the slides and not visit the breakout-groups uninvited.
You can choose to allow the students to look at the other groups’ slides. This gives an opportunity to help the students if they feel they get lost or need some ideas to proceed with the discussions.
You can review the slides from the different groups and make a summary after the group activity, prepare how to structure a discussion based on the points different groups wrote down, or how to proceed (giving students more or less time in the group, picking up or dropping a topic, …).
The students have access to the shared slides — and thus their combined notes — after the lecture
Anecdotal evidence, but students that are asked “which ice cube will melt faster, the one in salt water or the one in freshwater?” without also being asked to sketch the mechanism they base their answer on, almost always get it wrong (or right only for the wrong reasons). This year’s class all came to the correct response based on the correct mechanism (see below)!
Assigning responsibilities to break up established roles
Group dynamics can be tricky, and groups very easily fall into pattern that might engage students very unequally. To facilitate shared responsibility for taking notes, sticking to the topic of discussion, or reporting back from group work, you can assign and re-assign the roles based on semi-random criteria. For in-person teaching, you can use their birthday (e.g. birthday closest to Christmas, or ’today’), or other semi-random information to distribute roles. In online teaching, you can also use the students’ physical location as a criterion. You can, for instance, ask the student located furthest south/north/east/west to report back from the group. The students will need to first figure out who is responsible for each role and then follow through with that. Great icebreaker, and not always the same person taking notes or reporting back!
I’ve been talking about the importance of leaving room for topics that students are really interested in for a long time. Today, I want to tell you about my first experience with this:
Back in 2012, in my first year teaching the “introduction to oceanography course”, a student came up to me after the first lesson and told me that she had a part-time job in a company that builds oceanographic instrumentation: She had spotted one of the instruments the company sells on one of the slides with research cruise pictures that I had shown for motivation and could add some details on how it works. I was obviously excited to hear about her experiences and asked a couple of questions, so after a short conversation about how we both thought that knowing about practical aspects of how measurements are done is super excited, she invited us to a guided tour in her company.
A couple of weeks later, the whole class went on an excursion — with packed lunches and the whole class-trip feeling — and my student’s line manager and the student herself gave us a tour of the company. We got to see a presentation as well as doing a tour of the labs. Especially the labs were cool: My student was wearing the special kind of shoes that allowed her to walk wherever she liked, but the rest of us had to stay within narrow walkways that were marked on the floor with yellow tape so as to not bring any electric signals too close to sensitive instrumentation (or something like this, this was a loooong time ago!). And we got to see how the kind of instruments were produced that we would use on our own student cruise in this course only weeks later!
Even though I can’t remember the technical details of what we were told there (but I DO remember how they had different standards to calibrate turbidity meters with and I thought that was sooo fascinating), I vividly remember the excitement of the class, but most importantly the pride of the student who got to show us her company. The next year we went back with the next class I taught, and it was again exciting, but there was something really special about making time and going to the hassle of driving out to visit the company of one of the peers in the class.
So what I try to do now is to create this excitement and feeling of relevance because we are talking about something that came from within the group of students, by opening up opportunities where I explicitly ask for suggestions. I reserve parts of the class specifically for whatever students want to talk about, and whenever students show a special interest in a topic, I am happy to re-arrange my plans to make time for whatever is on their mind. This does get me the occasional “the red thread of this class wasn’t always clear” comment in evaluations, but I think it is so worth it (also I’m working on making the red thread clear when I return to it after any detour I might take to follow student interest ;-)).
What do you think? Have you tried this and what were your experiences?
I got permission to publish Kjersti Daae‘s iEarth conversation on teaching (with Torgny Roxå and myself in April 2021) on my blog! Thanks, Kjersti :-) Here we go:
I teach in an introductory course in meteorology and oceanography (GEOF105) at the geophysical institute, UiB. The students come from two different study programs:
Most students do the course in their third semester. They have not yet learned all the mathematics necessary to dive into the derivation of equations governing the ocean processes. Therefore, we focus on conceptual knowledge and understand the governing ideas regarding central ocean processes, such as global circulation and the influence of Earth’s rotation and wind on the ocean currents. The students need to learn how to describe the various processes and mechanisms included in the curriculum. I, therefore, use voting cards to promote student discussions during lectures.
I first heard about voting cards from Mirjam’s blog “Adventures in Oceanography and Teaching”. The method is relatively simple. You pose a question with four alternatives A,B,C,D, accompanied by different colours for easy recognition. The students have a printout each with the four letters on it.They spend a few minutes thinking about the question and prepare their answer. Then they fold their paper so that only one letter/colour shows, and hold it up and provide direct feedback to the teacher. The questions can, among others, be used to checking if the students understand a concept or let the students guess the outcome of something they haven’t learned yet.
However, I prefer to use voting cards to promote discussions among peers. This procedure is following the Think-pair-share method developed by Lyman (1981). By carefully selecting alternative answers, I can make it hard for the students to choose the correct answer, or the answers can be formulated so that the students can argue for more than one correct answer. When the students hold up their answers, they can look around at the other students’ responses and find someone with a different response than themselves. Then they can pair up and discuss why they answer differently and see if they can agree on one common answer before sharing their opinion with the rest of the class. During this exercise, the students practice talking about science and arguing for various answers/outcomes based on the voting cards’ questions.The exercises serve at least two purposes:
The student practice answering/discussing relevant questions for the final exam.
The students get active instead of listening passively to the lecturer.
Usually, I can see the students becoming very tired after 10-15 minutes of passive listening. These voting questions “wake up” the students, and after one such question, they tend to stay focused for another 10-15 minutes.
I think the voting cards work really well. When I display a question, the students usually move from a relaxed position to sitting more straight and preparing for being active. I can hear them discussing what they are supposed to. I also get very good feedback and responses in whole-class discussions/summaries following the discussions in pairs. Such summaries are especially interesting if multiple answers can be correct, depending on how the students argue. I can select responses from students based on their visible letters and make sure we can hear different solutions to the same question. During a semester, I see a clear development in the way students reflect on the various questions and express critical thinking governing oceanographic processes. The exercises show the students how important argumentation is. An answer with a well-founded argumentation and critical thinking is worth much more than just the answer/letter. My observation is consistent with Kaddoura (2013), who found that the think-pair-share method increased nursing students’ critical thinking.
Lyman, F. (1981). “The responsive classroom discussion.” In Anderson, A. S. (Ed.), Mainstreaming Digest, College Park, MD: University of Maryland College of Education.
Kaddoura, M. (2013). «Think Pair Share: A Teaching Learning Strategy to Enhance Students’ Critical Thinking», EducationalResearchQuarterly, v36 n4 p3-24
I just love giving students choice: It instantly makes them more motivated and engaged! Especially when it comes to big and important tasks like assessments. One thing that I have great experience with is letting students choose the format of a cruise or lab report. After all, if writing a classical lab report isn’t a learning outcome in itself, why restrict their creativity and have them create in a format that is — let’s be honest — super boring to read for the instructor?
I have previously given students the choice between a blog post, an Instagram post, and tweets, but would next time open it up to include other formats like tictoc or podcasts or even any social media format they like. What I did was give them the choice of format, and then also the choice of actually publishing it (on either a platform that I provided, or on one they organized themselves), or “just” submitting something that could have been posted on one of those platforms but ended up just visible to me and the class.
So how do we then make sure that the different formats all have the same level of “difficulty”, that it’s a fair assignment? This is where rubrics come in. Your rubric might assess several categories: First and foremost, the one directly related to your learning outcome. In case of a lab report things like is the experimental setup described correctly, does it become clear why an experiment is being performed and how it is done, are observations clearly described and results discussed etc.. All of these things can be done equally well in a twitter thread and in a blog post.
And lastly — you could require a reflection document in which students discuss whether they did address the different points from the rubric, and where they have the chance to justify for example why they did not include certain aspects in the social media post, but provide additional information in that document (for example if you would like to see the data in a table, that might not be easy to include in a podcast). Requiring this document has at least two positive effects: Making sure the students actually engage with the rubric, and levelling the playing field by giving everybody the opportunity to elaborate on things that weren’t so easily implemented in their chosen format.
If you want to make sure that students really feel it’s all fair, you could even negotiate the rubric with them, so they can up- or downvote whichever aspects they feel should count for more or less.
What do you think, would you give your students such choices? Or do you even have experience with it? We’d love to hear from you!
Last week, Kjersti Daae and I gave a virtual presentation at the iSSOTL conference, and here is a short summary.
We presented an ongoing teaching innovation project, funded by Olsen legat and conducted together with Jakob Skavang, Elin Darelius and Camille Li, that we started last year at the Geophysical Institute in Bergen: Bringing together third semester and fifth semester students to do tank experiments.
In our presentation, we touched on the literature inspiring the design of the teaching project, the study we have conducted, and then our results and conclusions.
Our main goal was to change the way students look at the world around them, by giving them a new perspective on things. A framework that describes this well are “transformative experiences” that I wrote about in more detail here.
Transformative experiences are awesome, because they trap you in a feedback loop: Once you have changed the way you look at the world and notice new things, this feels good and makes life more fun. Therefore you continue doing it voluntarily, noticing more cool things in a new way, feeling happier about it, and so on and so on.
One example of a transformative experience happening was described by Dario after we did some kitchen oceanography (more on that here).
But we don’t want people to go through the transformative experience alone, we want them to do it in a community of practice to support one another and create even more of a feedback. In our case, the community are our students at the Geophysical Institute, who share the interest in dynamics of the atmosphere and ocean and learn more about them by having shared experiences and discussions that they can refer back to.
The topic we wanted to address in our course and make the central topic of this community of practice is the influence of rotation on movement in the atmosphere and ocean. This is the central concept of geophysical fluid dynamics, but it is difficult to grasp because the scales in question are so large that they are difficult to directly observe, and the mathematical descriptions are difficult and unintuitive.
And here is where we invited the audience to become part of the very first steps in that teaching project.
We start out by making sure everybody has a good grasp of what happens in a non-rotating frame so we can later contrast the rotating case to something we know for sure people have seen before (we used to assume that people had a good grasp of what happens in non-rotating fluids, but this turns out to be very much not the case).
At this point in our demonstration, Kjersti showed a live demonstration! (And I was so fascinated that I forgot to take a screenshot)
Once we have established what pouring a denser fluid into a lighter fluid looks like in a non-rotating case, it is time to move on to a rotating case. Considering rotation when we talk about flows on the rotating Earth (in the atmosphere or ocean) needs to consider that the Earth has been spinning for a very long time. We can simulate that by rotating a bucket of water (which needs to rotate for a much shorter period of time because it is much smaller).
When we drip colour into a rotating bucket full of water, the way the colour distributes itself looks very different from what it looked like earlier in the non-rotating case. We now get columns of dye rather than the mushroom-like features.
These experiments are not difficult in themselves, but we wanted students to not just follow cookbook-style instructions, but to actively engage and discuss what they observe.
Therefore, we brought students in their third semester together with students in their fifth semester, who had done the same experiments in the previous year.
The idea was that the third semester students would receive guidance by the older students, and would be able to discuss hypotheses and make sense of their observations together. The presence of the fifth semester students would help them be less stressed about potentially making mistakes and help the labs run a lot smoother.
The fifth semester students had done the experiments in the previous year. We prepared them for their role (you don’t need to know all the answers! In fact, you are not supposed to even answer their questions. Help them figuring it out themselves by asking questions like “…”) and went through the experiments with them to refresh their memory and also talk about how they were understanding and seeing things differently now that they had another year of education under the belt compared to when they first saw the experiments.
And then for us: Distributing and sharing responsibility for learning is something we have been interested in for a while now (see blog post on co-creation here for more information). Having students so engaged in sense-making through discussions gave us a great opportunity to eaves-drop on their arguments and get a much better understanding of what they are thinking and which points we should address in more detail later.
In order to understand how this setup worked for the students, we collected several types of data: We had questionnaires aimed at the third semester students (testing specific learning outcomes, but also on their observations of roles and interactions, and interpretations of the situation) and fifth semester students (on observations of roles and interactions, and interpretations of the situation, and how they would compare the experience as “guide” to that the previous year). We instructors also took notes and reflected on our observations.
So what did we find?
The third semester students all perceived the presence of the older students as very positive and described the interactions the way we had hoped — that they weren’t being fed the answers, but asked questions that help them find answers themselves.
From the fifth semester students, we also got a very positive response. They especially focussed on how they had to think about what makes a good question or good instruction, and that that helped them reflect on their own learning. They also pointed out that the experience showed them how much they had learned during the last year, which they had not been aware of before.
They also really enjoyed the experience of being a teacher and interacting in that role.
Also looking at learning outcomes, we found that the third year students learned a lot more as compared to last year’s third year students (which is a bit of an unfair comparison since last year was dominated by covid-19 restrictions, but still that is the only data we have that we can compare to). Specifically, the misconception that “the centre of the tank is the (North) Pole” seems to have been eradicated this year (we’ll see if that holds over time).
One thing we noted and that students also pointed out as very helpful is that conversations did not just deal with the experiment itself, but that the younger students asked a lot of questions about other experiences that the older students had made already, like for example the upcoming student cruise. We had hoped that this would happen, and that these kind of conversations would continue beyond these lessons!
So this is where we ended our presentation and hoped to discuss a couple of questions with the audience. If you have any input, we would love to hear from you, too!
I’d love your input: If your student lab for GFD tank experiments had to downsize, but you had to present a “wish list” for a smaller replacement, what would be on that list? Below are my considerations, but I would be super grateful for any additional input or comments! :-)
Background and “boundary conditions”
The awesome towing tank that you have come to love (see picture above) will have to be removed to make room for a new cantina. It might get moved into a smaller room, or possibly replaced all together. Here are some external requirements, as far as I am aware of them:
the (new) tank should ideally be movable so the (small) room can be used multi-purpose
since the new room is fairly small, people would be happy if the new tank was also smaller than the old one
the rotating table is kept (and a second, smaller one, exists in the building)
There are other, smaller tanks that will be kept for other experiments, dimensions approximately 175x15x40cm and smaller
the whole proposal needs to be inexpensive enough so that the likelyhood that it will actually be approved is moderate to fair ;-)
Here are a couple of things I think need to be definitely considered.
Dimensions of the tank
If the tank was to be replaced by a smaller one, how small could the smaller one be?
The dimension of the new tank depend, of course, on the type of experiment that should be done in the tank. Experiments that I have run in the tank that is to be replaced and that in my opinion should definitely be made possible in the new location/tank include
“Dead water”, where a ship creates internal waves on a density interface (instructions)
Internal lee waves & hydraulic jumps, where a mountain is moved at the bottom of the tank (instructions)
Surface waves running up on a slope (I haven’t blogged about that yet, movies waiting to be edited)
If we want to be able to continue running these experiments, here is why we should not sacrifice the dimensions of the tank.
Why we need the tank length
The first reason for keeping the length of the tank is that the “mountains” being towed to create the lee waves are already 1 and 1.5m long, respectively. This is a length that is “lost” for actual experiments, because obviously the mountain needs space inside the tank on either end (so in its start and end position). Additionally, when the mountain starts to move, it has to move for some distance before the flow starts displaying the features we want to present: Initially, there is no reservoir on the “upstream” side of the mountain and it only builds up over the first half meter or so.
The second reason for keeping the length of the tank are wave reflections once the ship or mountain comes close to the other side of the tank. Reflected surface waves running against the ship will set up additional drag that we don’t want when we are focussing on the interaction between the ship and the internal wave field. Reflected internal waves similarly mess things up in both experiments
The third reason for keeping the length of the tank is its purpose: as teaching tank. Even if one might get away with a slightly shorter tank for experiments when you just film and investigate the short stretch in the middle of the tank where there are no issues with either the push you gave the system when starting the experiment or the reflections when you get near the end, the whole purpose of the tank is to have students observe. This means that there needs to be a good amount of time where the phenomenon in question is actually present and observable, which, for the tank, means that it has to be as long as possible.
Why we need the tank width
In the experiments mentioned above, with exception of the “dead water” experiment, the tank represents a “slice” of the ocean. We are not interested in changes across the width of the tank, and therefore it does not need to be very wide. However, if there is water moving inside the tank, there will be friction with the side walls and the thinner the tank, the more important the influence of that friction will become. If you look for example at the surface imprint of internal wave experiment, you do see that the flow is slowed down on either side. So if you want flow that is outside of the boundary layers on either side, you need to keep some width.
Secondly, not changing the tank’s width has the advantage that no new mountains/ships need to be built.
Another, practical argument for a wide-ish tank (that I feel VERY strongly about) is that the tank will need to be cleaned. Not just rinsed with water, but scrubbed with a sponge. And I have had my hands inside enough tanks to appreciate if the tank is wide enough that my arm does not have to touch both sides at all times when reaching in to clean the tank.
Why we need the tank depth
The first reason for keeping the height is that for the “dead water” experiment, even the existing tank is a lot shallower than what we’d like from theory (more here). If we go shallower, at some point the interactions between the internal waves and the ground will become so large that it will mess up everything.
Another reason for keeping the depth is the “waves running up a slope” experiment. If you want waves running up a slope (and building up in height as they do), you have the choice between high walls of the tank or water spilling. Just sayin’…
And last not least: this tank has been used in “actual” research (rather than just teaching demonstrations, more on that on Elin’s blog), so if nothing else, those guys will have thought long and hard about what they need before building the tank…
Historical images of research on internal lee waves being done with the tank
Without getting too philosophical here about models and what they can and cannot achieve (and tank experiments being models of phenomena in the ocean), the problem is that scaling of the ocean into a tiny tank does not work, so “just use a mountain/boat half the size of the existing ones!” is actually not possible. Similarly to how if you build the most amazing model train landscape, at some point you will decide that tiny white dots are accurate enough representations of daisies on a lawn, if you go to a certain size, the tank will not be able to display everything you want to see. So going smaller and smaller and smaller just does not work. A more in-depth and scientific discussion of the issue here.
Other features of the tank
When building a new tank or setting up the existing tank in a new spot, there are some features that I consider to be important:
The tank needs a white, intransparent back wall (either permanently or draped with something) so that students can easily focus on what is going on inside the tank. Tank experiments are difficult to observe and even more difficult to take pictures of, the better the contrast against a calm background, the better
The tank should be made of glass or some other material that can get scrubbed without scratching the surface. Even if there is only tap water in the tank, it’s incredible how dirty tanks get and how hard they have to be scrubbed to get clean again!
The tank needs plenty of inlets for source waters to allow for many different uses. With the current tank, I have mainly used an inlet through the bottom to set up stratifications, because it allowed for careful layering “from below”. But sometimes it would be very convenient to have inlets from the side close to the bottom, too. And yes, a hose could also be lowered into the tank to have water flow in near the bottom, but then there needs to be some type of construction on which a hose can be mounted so it stays in one place and does not move.
There needs to be scaffolding above the tank, and it needs to be easily modifiable to mount cameras, pulleys, lights, …
We need mechanism to tow mountains and ships. The current tank has two different mechanisms set up, one for mountains, one for ships. While the one for the ship is home-made and easily reproducible in a different setting (instructions), the one to tow the mountain with is not. If there was a new mechanism built, one would need to make sure the speeds at which the mountain can be towed matches the internal wave speed to be used in the experiment, which depends on the stratification. This is easy enough to calculate, but it needs to be done before anything is built. And the mechanism does require very securely installed pulleys at the bottom of the tank which need to be considered and planned for right from the start.
“Source” reservoirs
The “source” reservoirs (plural!) are the reservoirs in which water is prepared before the tank is filled. It is crucial that water can be prepared in advance; mixing water inside the tank is not feasible.
There should be two source reservoirs, each large enough to carry half the volume of the tank. This way, good stratifications can be set up easily (see here for how that works. Of course it works also with smaller reservoirs in which you prepare water in batches as you see below. But what can happen then is that you don’t get the water properties exactly right and you end up seeing stuff you did not want to see, as for example here, which can mess up your whole experiment)
Both reservoirs should sit above the height of the tank so that the water can be driven into the tank by gravity (yes, pumps could work, too, more on that below).
“Sink” reservoir
Depending on the kind of dyes and tracer used in the water, the water will need to be collected and disposed of rather than just being poured down the drain. The reservoir that catches the “waste” water needs to
be able to hold the whole volume of the tank
sit lower than the tank so gravity will empty the tank into the reservoir (or there needs to be a fast pump to empty the tank, more on that below)
be able to be either transported out of the room and the building (which means that doors have to be wide enough, no steps on the way out, …) or there needs to be a way to empty out the reservoir, too
be able to either easily be replaced by an empty one, or there needs to be some kind of mechanism for who empties it within a couple of hours of it being filled, so that the next experiment can be run and emptied out
If the waste water is just plain clear tap water, it can be reused for future experiments. In this case, it can be stored and there need to be…
Pumps
If reservoirs cannot be located above and below tank height to use gravity to fill and empty the tanks, we need pumps (plural).
A fast pump to empty out the tank into the sink reservoir, which can also be used to recycle the water from the sink reservoir into the source reservoirs
One pump that can be regulated very precisely even at low flow rates to set the inflow into the tank
Preferable the first and the latter are not the same, because changing settings between calibrating the pump for an experiment, setting it on full power to empty the tank, and calibrating it again will cause a lot of extra work.
Inlets for dyes
Sometimes it would be extremely convenient if there was a possibility to insert dyes into the tank for short, distinct periods of time during filling to mark different layers. For this, it would be great to be able to connect syringes to the inlet
Hoses and adapters
I’ve worked for years with whatever hoses I could find, and tons of different adapters to connect the hoses to my reservoir, the tap, the tank. It would be so much less of a hassle if someone thought through which hoses will actually be needed, bought them at the right diameter and length, and outfitted them with the adapters they needed to work.
Space to run the experiment
The tank needs to be accessible from the back side so the experimenter can run the experiment without walking in front of the observers (since the whole purpose of the tank is to be observed by students). The experimenter also needs to be able to get out from behind the tank without a hassle so he or she can point out features of interest on the other side.
Also, very importantly, the experimenter needs to be able to reach taps very quickly (without squeezing through a tight gap or climbing over something) in case hoses come loose, or the emergency stop for any mechanism pulling mountains in case something goes wrong there.
Space for observers
There needs to be enough room to have a class of 25ish students plus ideally a handful of other interested people in the room. But not only do they need to fit into the room, they also need to be able to see the experiments (they should not have to stand in several rows behind each other, so all the small people in the back get to see are the shoulders of the people in front). Ideally, there will be space so they can duck down to have their eyes at the same height as the features of interest (e.g. the density interface). If the students don’t have the chance to observe, there is no point of running an experiment in the first place.
Filming
Ideally, when designing the layout of the room, it is considered how tank experiments will be documented, i.e. most likely filmed, and there needs to be space at a sufficient distance from the tank to set up a tripod etc..
Lighting
Both for direct observations and for students observing tank experiments, it is crucial that the lighting in the room has been carefully planned so there are minimal reflections on the walls of the tank and students are not blinded by light coming through the back of the tank if a backlighting solution is chosen.
Summary
In my experience, even though many instructors are extremely interested in having their students observe experiments, there are not many people willing to run tank experiments of the scale we are talking about here in their teaching. This is because there is a lot of work involved in setting up those experiments, running them, and cleaning up afterwards. Also there are a lot of fears of experiments “going wrong” and instructors then having to react to unexpected observations. Running tank experiments requires considerable skill and experience. So if we want people using the new room and new tank at all, this has to be made as easy as possible for them. Therefore I would highly recommend that someone with expertise in setting up and running experiments, and using them in teaching, gets involved in designing and setting up the new room. And I’d definitely be willing to be that person. Just sayin’ ;-)
