First of all, could you please briefly introduce your research team, Fluid-Based Convergence Lab?

A. __ As the word itself implies, a fluid is a flowing object. As such, it is a field where anything can be studied except solids. We are converging our research with other disciplines, based on fluid dynamics. For example, we are conducting research on how the wind flows, how we can increase lift force, or how we can reduce noise.

It seems to be extremely wide ranging. What are your main areas of research?

A. __ We have been conducting research on convergence with biology for quite a long time, and have obtained several achievements, one of which is the “low-noise, high-efficiency air conditioner fan.” In general, the outdoor unit of an air conditioner is installed on the outer wall of a building, so the biggest problem is the noise it generates. Existing fans generate a complicated airflow when they’re rotating, thereby increasing the noise while reducing the air conditioner’s efficiency. However, based on our industry-academic research, we found the answer in humpback whales and shellfish. Our study showed that a humpback whale has small bumps on the front of its pectoral fins, which help it to reduce eddy currents and maintain lift force when it suddenly changes its body‘s position or its direction in the water, enabling it to move quickly. In addition, we found that shellfish have a grooved structure on their surface, so they too can move quickly when avoiding predators or hunting prey. By applying the principle of this biological structure to an outdoor unit fan, we succeeded in decreasing noise by 2dBA (A-weighted decibels) and reducing power consumption by 10%. A product made with this technology is now being sold.

It is extremely interesting that you discovered this principle in the fins of a humpback whale. I’ve heard that you have also achieved a new result by simulating the structure of a humpback whale.

A. __ Analysis of a whale swimming in the sea shows that it has a hydrodynamic structure, which is in some ways similar to that of a flying bird in the sky. That is to say, a whale generates lift force by deflecting the flow of water with its fins, while a bird generates lift force by going with the flow of the wind with its wings. This is also the reason why we imitated the structure of a humpback whale while carrying out our paraglider development task. We found out that humpback whales can leap powerfully out of the water and then fall to the surface because of the tubercles on their large pectoral fins; so, by applying that structure to a paraglider, we were able to enhance the speed and flight distance of a paraglider.

Could you tell us which areas specifically have been improved?

A. __ A paraglider can fly about 300 km at the most, but of course it varies with depending on the wind. The angle at which wings meets the wind is called “the angle of attack,” and in paragliders, this angle of attack changes a lot, so the wings must be designed to obtain lift force over a very wide range of angle of attack. It has already been proven in other studies that the bumpy tubercles on a humpback whale’s pectoral fins allow it to swim better. Thus, it was important to verify whether the same result could be achieved when applied to a paraglider’s wings. So we designed a bumpy wing and confirmed its performance numerically. Then, as the last step to commercialization, we tested its performance and safety by participating in the International Paragliding World Cup. At the first competition, our product took 3rd place, at the second, 1st place, and at the third, the players who participated with our product won 1st, 2nd, and 3rd places, completing the test successfully. At present, the mass production of the actual product has been completed.

How did you start developing paragliders?

A. __ Engineers are always interested in developing practical technologies. This is why a lot of industry-academic studies are being conducted. While we were looking for a suitable task for our research team, we learned about the key technology support project for leading sports companies, which was hosted by the Ministry of Culture, Sports and Tourism, and among the participants, the company we could approach with an idea about hydrodynamics was “Gin Gliders”, a manufacturer of paragliders. From the moment when we decided to take up the challenge, I, along with the students in our team, started studying paragliders in earnest. After selecting four to five applicable fluid mechanics technologies, we proposed to Song Jin-seok, the CEO of Gin Gliders, that we simulate them together, and began their full-scale development.

Did any difficulties arise while you were carrying out the task?

A. __ In fact, we failed in the first year of our challenge for the supporting project. As I was sure that we had confirmed the possibility of success, the result was all the more disappointing. However, we didn’t give up and continued working on industry-academic research with Gin Glider for one more year. Although we lacked research funds and had many difficulties in various areas, we made good progress in developing the technology to the extent of making prototypes.

Although it was a difficult situation, what drove you to complete the development of the product?

A. __ Fortunately, we were selected for the same support project the following year and received a stable supply of research funds. Our year of hard work was recognized. Usually, even if research succeeds, it takes a long time for a product to be commercialized. In the case of the outdoor unit fan, it took three years to get it mass produced. This was because the entire production process needed to be modified, whereas for the paraglider, all the processes were completed within two years. That’s because paragliders are made to order and most of the processes are done by hand, so a newly changed technology can be applied right away.

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What is the next area of study of your research team?

A. __ having started with paragliders, we intend to continue our research in the field of sport. Currently, we are conducting industry-academic research related to archery, in preparation for the 2024 Summer Olympics in Paris. While participating in the research I discovered that, as with paragliders, the archery market has also developed equipment in an unscientific way. When research is conducted according to a scientific approach, the existing technology can be changed in innovative ways. I think that paragliding is a good example of that. With our archery research, we are trying to improve the structure of bows and arrows by applying the structure of the anemophilous plant, which distributes pollen via the wind, and we hope that this will lead to good results.

Lastly, could you tell us if there is a new direction that your team intends to follow in the future?

A. __ When students are about to graduate from a doctor’s course, they tend to end up resembling their tutor. It was like that for me. I guess it’s because we spend the most important time together as researchers. However, I hope that the students in our research team will be able to grow and develop their individuality instead of becoming like me. Thus, even in the process of leading the research team, I try to create an atmosphere in which students are free to do what they want to do. I tend to tell them to do whatever they want to do without going too far in the wrong direction. Therefore, one could say that the direction of our research team is up to our students. We will continue to do our best to achieve good results in our own way!