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Background information of the project:
The bubble generation project is one that is done in collaboration with Hyflux to do aeration diffuser design study for the Membrane Bioreactor (MBR) water filtration system. The aeration of the MBR is to make use of rising bubbles to shake the filtering membranes in order to remove dirt particles on the filters to maintain efficiency of the filtration system. It is funded by MOE with a budget of $50,000 on the experimental set up which includes an air support system, a water tank and specimens in the water tank, which currently include aeration pipes and a bubble generation plate, with the high-speed camera alone costing $50,000. For the Final Year Project (FYP in short) that was to be done by a final year student, which is also one of our mentors, he got $600 for the purchasing of the chemicals needed. Currently, the set up only takes up a corner of the hydraulics lab at SIT with 2 professors, 2 researchers as well as 3 students using it. At the point I joined the project, it is already in “stage 2” where preliminary research has already been completed last year and it is now given to final year students as their FYPs to conduct experiments according to their own plan and to collect additional data for the bigger research task.
Picture 1:The area of the experimental set-up in the lab.
Picture 2: The set-up itself.
Picture 3a and 3b: Photos with our two main mentors, Joo Guan (on left) and Shuek (on right).
Elaboration on the project and its purpose:
This project is created to find the optimal bubble size as well as the frequency to be used to clean dirt and other impurities that got caught by the filter fibres after the water is cleaned by the filter. When this project can be successfully completed, it will bring about many benefits, such as increased efficiency of the filtration system, reduced power consumption and therefore reduced operation costs as well as being indirectly more environmentally friendly. The steps to complete the project includes testing the viscosity of different mixtures of glycerin as well as water in small samples, increasing the glycerin-water mixture to a suitable height when conducting the experiment and finally turning on the air flow, recording the bubble flow using the high-speed camera and finally analyzing it using the analysis app.
Elaboration on tasks that we participated in:
Despite not having a final product or result to work to, we did not just sit around and do nothing and instead we participated in a few different experiments to learn about the project as well as knowledge that is related to the project. Firstly, Joo Guan, our first mentor, gave us the tasks to read 2 different papers as an introduction, then we tested for the specific flow rate which slugging will stop in the case of a pipe with 5 holes of 5mm in diameter each. The specific flow is one that will cause slugging to stop when the set flow rate is higher than this value and slugging will occur when the set flow rate is lower than this value. Slugging is a phenomena where the waves of the water in the pipe becomes high enough to reach the top of the pipe, thus causing the air flow to not be continuous. Not only so, we also measured and calculated the critical height of the liquid in the pipe which would cause slugging to occur as well as having to find out why the calculated and measured values are different. After this introductory experiment and reading was done, we went on to attach to the main project that aims to find the optimal flow rates for holes of different diameters in different viscosity of the liquid used. This project is being done by Shuek, our second mentor. This experiment started with using a digital viscometer to measure the viscosity of samples of different ratios of glycerin and water which was done by Shuek and a friend while we observed them. After that, it was just testing different flow rates with a fixed hole diameter and recording and analysing the captured footage of the bubbles using a high-speed camera. This was all done in just water and can be considered as the collection of data for the "mixture" that is 100% water. After that, some planning was done to devise a plan to do the main experiment with accuracy and speed. With a limited budget given to the FYP, there was only enough money to get enough chemicals to do the actual experiment once and only once, therefore with a tense heart we started the experiment. As per what we have planned before, we started with 100% glycerin (as shown in the pictures above) and added water afterwards, to lower the concentration of glycerin and hence the viscosity. After obtaining the first data set with 100% glycerin, the diameter (of the widest point) of the bubble was measured and the bubble modeled and verified using SolidWorks, a 3D modelling application. When the first set of data was verified to be accurate (and thus the experiment was proven correct), all the data sets collected afterwards were just saved as videos due to limited time and many sets of data that are needed to be collected.
Picture 4: Adding glycerin into the water tank.
Picture 5: Adding in containers of water to make the glycerin reach a desired height.
Picture 6: Analysis of bubbles.
3 content knowledge/skills I learnt:
- How to use the air supply system using compressed air, why is it used as well as some of the essential procedures regarding it. Despite the presence of a main air compressor pipeline nearby, the experimental set-up did not draw compressed air directly from it but instead stored air at a needed pressure in air canisters below the set-up. This was done as pressurized air canisters at a constant pressure provided a more consistent flow or air compared to active pumps. The air flow regulators at the left side of the water tank are also separated from the pipe that leads to the water tank by a pressure chamber at a higher elevation to prevent water from going into the electronics and making them out of order. The flow rate of air into the test specimen in the water tank can be controlled by a control panel at the top left corner of the set-up with other functions that can be controlled as well such as backlights and water height regulation. The system was also surprisingly easy to use as the desired flow rate can be set and the regulators can be turned on and off using switches on the panel. Not only so, the flow rate can be controlled to the nearest 0.1 standard litres per minute (SLM) as there are regulators with different maximum flow rates such as 100 SLM, 50SLM, 10SLM and 1SLM.
- Another skill that i have learnt would be the usage of high-speed camera to record and do preliminary analysis of bubbles generated. I was also surprised at first by the fact that unlike normal cameras, the high-speed camera does not have a screen to view the captured footage and would have to be connected to a computer or laptop to even operate it. The apps that are used to view and control the camera came along with it as any other applications would not be able to do such a thing. The capturing app can also do preliminary analysis of the dimensions of the bubble as it would be able to measure lengths straight from the footage captured, however, the length has to be calibrated with a certain known length first before any measurement can be done. The known length that it is calibrated against is usually another aeration hole on the bubble generation plate for convenience and accuracy.
- Despite not being able to be involved in a simulation, in this case, Computational Fluid Dynamics (CFD), due to the lack of time, we still learnt quite a bit about how simulations are done for travelling entities which can be either solids or fluids (liquids and gases). For the simulation for moving solids, the motion for every part of the solid can be tracked individually as solids usually stay in the same shape and size throughout most, if not all of their journey. On the other hand, it would be impractical to track every individual part of a fluid due to its nature to change shape and size during its travel, costing more time and having a need for a greater amount of computing power in order to run that simulation. Due to these reasons, a different method is used for the simulation for movement of fluid, this method is called "meshing". This method works by dividing the area which the fluid will be in into small cubes where the fluid itself is not tracked but the contents and position of the contents in the small cubes are tracked (e.g. 50% water and 50% air with air above the water). After all the cubes are tracked, the movement, velocity and other parameters of the flowing fluid can be mapped out and allowing the simulation to be done easier.
2 interesting aspects of my learning:
- The first interesting aspect would be that experimental projects are not just about repeated experiments again and again with nothing else to do, instead, experiments themselves only take up a portion of the time that is spent on the project. The other portion of the time will be spend on other perhaps not so interesting but still essential for the progress of the project such as research, project planning, material acquisition and processing of the data collected.
- The second interesting aspect would be that i thought that experiments are going to have a rigid process and fixed way of doing due to the numerous rules and regulations that are in place during lab experiments. However, it turns out that there is still much room for innovation as the rules are a general guideline on what to do and what not to do in a lab.
1 takeaway for life!
I think my takeaway for life from this month long WOW! programme would be the qualities needed to successfully do a long-term research project well, these qualities will also be applicable later on during work in terms of almost any type of projects. This is because projects usually do not have very clear instructions on what to do but only provide a general overview of the field where research should be done in. Due to that reason, an important quality to have is a clear mind on what is the goal to be achieved by the end of the research project so that it would be focused on and that the research (or work) will not go off plan. Not only so, time management skills would also be vital to the success of such long-term projects due to the sparse and limited amount of progress checks there are, there is probably only monthly, if not quarterly progress reports depending on the length of the project. Due to the loose checking of progress, it would be easy to waste large amounts of time on other fun-but-not-helpful activities such as checking social media, for example. Therefore, good time management skills would allow us to keep ourselves on track and not end up with the consequences of incomplete work despite the time given. Lastly, as there is usually limited budget given to such projects, a creative mind would also be needed to find materials and other essential resources that will both work well and be friendly to the wallet. Not only will creativity be needed to make progress on projects, it would also be needed to solve problems that will crop up along the way of the project (just like how the liquid level would be insufficient to conduct the experiment, needing to use bottles of water to make it high enough which can be seen in Picture 5).
All in all, this month long WOW! programme was really beneficial and insightful for me as not only did I get to do something that I have never done before in my school life, but also learn numerous skills and knowledge that would either be difficult to obtain in a school environment or will only be taught at a much later time. Therefore, I am very grateful that the school provided me with such a rare and useful opportunity to be attached to a external organisation of my choice for one month to both learn and have a feel on what working might be like in the future.
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