Yuan: AP Research Project

Blog 2 - Research Update

Intro

My project looks at the drag effects of water on different skin structures. I will be testing two different species from different environments: the open ocean dwelling shortfin mako and the river native European Sea Bass. Using a 3D printer, I will be replicating the major aspects of their skin patterns and testing the drag reduction by flowing water along them at different speeds in order to mimic different hydrodynamic conditions. Ultimately, I hope this research can apply to watercraft to see what structures, optimized by evolution, will reduce their drag in different waters.

Zoomed in 3D print design for mako riblets

Equation to determine fluid turbulence

Progress

Throughout the data collection process, my main goals have been related to the construction of my 3D printed test tubes. In the last month, I've had to conduct a lot more research on both the mako and bass in order to analyze their skin structures. Through this research, I've gotten to learn a lot more about what physics processes are at play between the scales and water.

For makos, thin riblets in an alternating pattern align the flow of the water to reduce counteracting currents, while for the bass, in a process known as streamwise streaking, long streaks of air are formed by the scale morphology to reduce friction between the water and skin boundary.

I've been extremely successful in mapping the precise dimensions of the shortfin mako's riblets, including their height, length width, and various spacings. While the scale structures are complex, its replication in studies I've read are relatively simplified. As a result, I've been able to use a free online CAD engineering tool known as TinkerCAD. As of now, I have my scale pattern for the mako fully completed and scaled properly! For the sea bass, I have also ordered the alternative mold which I will get into the challenges section! Also, through research on Reynolds number (the equation to the left), I have determined that by increasinf the fluid flow rate, I can increase the turbulence of the water. The next steps are finalizing my print and designing the test tube the water will flow through before I begin the physical experiment.

Challenges

Since data collection began, I've run into a few major issues that were overlooked in my preliminary research. The main one is the replication of the European Sea Bass skin surface. While the mako was an extremely well researched creature for this exact effect, when looking for a turbulent water-dwelling specimen with a proven benefit in surface drag reduction, species were hard to come by. The European Sea Bass has been studied in one reputable experiment that proved its promise in hydrodynamics, in addition to it fitting all of the criteria above. Additionally, its scales are oriented in a way that promotes streamwise streaking, which is a highly tested phenomenon in drag reduction.

But because of the lack of analysis on the skin of the European Sea Bass specifically, I ran into the issue of a lack of data on certain aspects of its scale dimensions such as the vertical length between the right and left intersecting scales and the central scales seen in the image as well as the horizontal width of each scale. Therefore, I wasn't able to draft a CAD design that replicated bass scales.

However, through more research, I came across a seafood culinary and engineering company called MoldBrothers that specializes in 3D printed molds of animal morphologies in culinary artistry. One mold available for purchase belonged to the skin surface of the European Sea Bass, created using computer imaging from freshly caught supply. After more research and a discussion with my supervisors, I was permitted to test using this mold and comparing it with the mako mold I designed myself.

This presented another problem. Because the mold I ordered was a flat surface, I couldn't test it in a tube as I had planned. However, using some preliminary sources for justification, I plan on using the molds as one side of a rectangular test pipe. While the drag reduction effect may be less noticeable, by adapting my other prints, I will be able to compare the different skin patterns effectively.

Attempted Sea Bass blueprint

Bass Scale imaging

European Sea Bass mold from MoldBrothers

Simplified blueprint for mako riblet pattern

Some Data Highlights!

My current data consists of the dimensions of my test tubes thus far, both researched and determined for my experiment. Each tube will have a square cross section with a length of around 3.8 cm to fit the water pump I plan on purchasing for the experiment. The riblets of the shortfin mako come in two types. Both are approximately, 0.21 mm in width and 0.3 mm in height. However, their lengths are 2.4 mm and 1.7 mm respectively, aligned in an alternating pattern and oriented parallel. Each riblet has 0.6 mm of width-wise spacing and 1.2 mm of length-wise spacing between each other. While the MoldBrothers' design doesn't include specific dimensions, I've estimated each scale to be around 50 mm in length and width in an alternating semicircle-like pattern. Stay tuned for blog post 3 where I will have the remaining data from my drag reduction experiment using these molds!

Reflection

Throughout this research process, I've learned a lot about myself as a researcher including many of my strengths and weaknesses. The biggest tendency I've noticed is that I like to jump from one problem to the next, tackling bite sized portions. I've seen this as both a strength and a weakness. This fast research process allows me to address many aspects of my project at once in order to gauge my overall process. I've also found it helps to take some time away from one issue I'm struggling with and moving onto a new one, coming back with a fresh perspective. I've especially noticed this as I've been working on my sea bass and mako molds, darting between both. However, I have noticed this can lead to procrastination. I've seen myself step away from a specific problem to tackle easier ones, and then putting off solving the original. To fix this, the key is balancing the various aspects of my project, but reminding myself to return to the parts of my project I might be afraid to address.

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