Interviews & Opinions


<OIST> Shedding light on the mechanics of diverse natural phenomena from the perspective of fluid mechanics — An interview with Dr. Pinaki Chakraborty


Promoting international research mobility and creating international talent circulation is an essential condition for robust research and development. To this end, it is important to internationalize the research ecosystem, promote international human resource exchange, and ensure that Japan is firmly integrated into the international brain circulation network. Under this special topic, we will introduce the current status and challenges of Japan's research efforts to promote international brain circulation to produce outstanding research results as well as the attractiveness of Japan's research environment, which is the key to attracting foreign researchers, through a series of interviews with relevant people in the field. In this interview we spoke to Dr. Pinaki Chakraborty, Principal Investigator of the Fluid Mechanics Unit at OIST.

Fluid mechanics is a field that spans many different disciplines such as physics, physical chemistry and engineering, and underlies many of the natural phenomena of our world and the wider universe; typhoon intensity, the creation of moon crater rays, friction in a water/oil pipeline, the shape of volcanic plume or blood flow in an artificial heart or valve, among other areas.

In our final interview at OIST (the Okinawa Institute of Science and Technology), we spoke with Professor Pinaki Chakraborty, a researcher of Indian origin, who heads the Fluid Mechanics Unit, and heard about his interesting world crossing journey to OIST, the surprising depth of fluid mechanics research, the benefits of working at an international research institution in Japan as a foreign researcher as well as the importance of international brain circulation for creative research outcomes.

Dr. Pinaki Chakraborty, principal investigator of the Fluid Mechanics Unit, enthusiastically explaining his past research.

A fortunate series of events leads to Illinois then Okinawa

Dr. Chakraborty followed an interesting path to his current research position. As a high‐school student in India, he was not particularly interested in studying or exams, but a chance meeting with a retired physics professor led to an informal mentorship outside of school which sparked a newfound fascination with the field of mechanics. "He was a very strict person and had a big influence on my life. He started to explain things in a way that helped me to understand concepts, as opposed to just schoolwork given to me. For the first time, I started to understand the relevance of things that I could see around me. The first things talked about were in the field of classical physics, specifically, mechanics. And from then I became extremely interested in mechanics."

India is the most populous country on earth (India has reportedly overtaken China this year), and as a result, a huge number of people are competing for very few positions. Chakraborty commented on this, saying, "During high school in India, as in many other countries, you are being prepared to pass exams. It is very competitive, where the idea is not selection [of the best students], but elimination! The exams are set‐up to test how many problems students can answer in a short period." This approach didn't resonate with Chakraborty, as he was more interested in understanding the concepts and underlying mechanics of the phenomena he was being taught. This approach to learning isn't the most efficient way to succeed in a school environment but was a perfect fit for understanding the field of classical mechanics.

Following high school, he focused on pursuing a degree in university that would be of practical use after graduation. With the background he had gained in mechanics through his mentorship, he felt that moving into engineering matched his interests and knowledge the best, saying "I looked at different branches of engineering for undergraduate study and the one that overlapped the most with mechanics was mechanical engineering," and so he pursued a degree in mechanical engineering at the National Institute of Technology in Surat, India.

After obtaining his Bachelor of Engineering, a series of chance events and encounters then led Chakraborty first to the US, and then to OIST in Japan. According to him, study into mechanical engineering usually leads to the approach of figuring out the applications of a particular concept and puts a lesser focus on understanding the underlying ideas. This drove him to seek further study, and when thinking of further study, especially postgraduate and beyond, most people will immediately dream of entering one of the top institutes in the US or Europe. This desire led Chakraborty to the University of Illinois at Urbana‐Champaign, "I wanted to study more, and I found a program which was called 'Theoretical and Applied Mechanics', which was at the intersection of engineering, physics and applied math, precisely what I was looking for." The next leg of his journey had begun.

Chakraborty obtained both a master's and PhD during his time in the US, and towards the end of his study, he had another chance encounter which affected the course of his research life. A faculty member who had just joined the university's Department of Geology started to circulate a picture of an unusually shaped volcanic plume to many people in engineering, inviting them to come up with some insights. As typical of his way of approaching study, he became interested in trying to shed light on the underlying mechanics of the plume, using his knowledge of fluid mechanics.

A volcanic plume is a mixture of gas, ash and other materials ejected during a volcanic eruption. As it rises, the plume mixes with the ambient air, and once the rising materials are of the same density of the air, it spreads horizontally and creates a large umbrella shape, the umbrella region. There are some interesting shapes in this umbrella that can be understood through both mechanics and mathematics. After his PhD graduation, the professor who circulated the picture of the unusual plume provided him with a unique position at the university's Department of Geology, "I was offered a very cozy post‐doc position where I had absolute freedom to pursue whatever problem I wanted." Chakraborty continued by adding that this was rare in the US, where narrowly defined goals and targets are the norm.

This position allowed him the freedom to examine these plumes from various viewpoints. When a volcanic plume rises to 10‐15 kilometer high, close to the tropopause, it spreads out, creating the typical 'umbrella' shape. It was understood that motion inside of this rising plume is vertical, and then radiates outwards, but during his research Chakraborty discovered that there is also rotation about the vertical axis of the plume, termed a "volcanic mesocyclone". He publicized this discovery in Nature in 2009.

After some time in this position, Chakraborty decided to look for a more standard faculty position, and submitted some applications. It was at this point that he got a message from OIST and decided again to take a chance and check out this new opportunity. It was here that the winds of fortune almost blew in the opposite direction, and weather tried its hardest to get in the way. "I was living in Illinois, and my interview for OIST was in December. I went to the airport, but I found my flight got canceled because of a snowstorm." Chakraborty confessed that he hates flying, and he almost took this as destiny telling him not to go. However, the flight to Japan and the interview at OIST were rescheduled after several days. "When I came here, it really changed my life in another way. I came from the middle of corn fields in Illinois and was bowled over by the natural beauty of the place."

Chakraborty had a few questions before he could decide, however, "When Dr. Jonathan Dorfan, the President of OIST, explained to me the concept of the new school, I had lots of reservations. This is a completely new place, what kind of university is it going to be? I was hesitant to join the traditional Japanese university system which is very different from the American system that I was used to." Another important consideration was the fact that in many institutions around the world, researchers are in an endless rat‐race of applying for grants to continue their research. Chakraborty already had a position with a great deal of autonomy, and no need to apply for these grants. "So, why come here [to OIST]? It had to have some other additional benefits. The biggest benefit from my point of view is the concept of high trust funding." He continued, touching on one reason why OIST has been so successful.

"After talking with the President, I came to know that this is a U.S.‐like system, it's a completely English language university and, additionally, it has this model of high trust funding. From a university point of view, these three things were extremely attractive to me," he recalled, "Other than that, I fell in love with Okinawa. I just absolutely like the place, and more than the place, which is stunningly beautiful, I like the people who live here. I also like that people can live here comfortably in safety and security. There are always little things here and there that sometimes bother me, but considering everything, I have to say OIST is as good as it gets." Chakraborty had nothing but praise for the university and islands that he now calls home.

A series of chance events, opportunities and decisions led Dr. Chakraborty from private tutoring as a high‐school student in India to his current work as a professor at OIST. Audaciously taking the chances provided to him and experiencing many different environments and research areas has given him a unique perspective and allowed him to make some breakthrough research findings across a range of topics. His rich experience and movement crossing borders show that international brain circulation is of great benefit to both individual scientists and the institutes where they research and should be encouraged further into the future.

Pipe flows, typhoons, comets, and volcanics ‐ The wide world of fluid mechanics

When one hears the term 'fluid mechanics', the flowing of water, or similar concepts, may come to mind. "When we talk about fluids, we are referring to things like liquids, like water, but we are also referring to gases. So, in the study of fluid mechanics, liquids as well as gases are treated as fluids." However, Chakraborty shared that the field is much, much deeper than just this, one example that might be overlooked, or not even considered to be 'flow', are the crater rays seen on the moon. Crater rays refer to the long, radial streaks seen extending from the impact craters that make the moon's 'Swiss cheese' image so famous. It was long thought that these were formed from volcanic activity, but actually they are the result of meteorites striking the surface of the moon, powdering the crust, and scattering that powder in the form of rays.

Chakraborty spent some time looking at this phenomenon together with a post‐doc, struggling to make inroads into the underlying mechanism behind the rays, among other questions. "It has been a huge mystery as to how these rays are formed. Why isn't this powder just emplaced in a uniform blanket across the crater? Why does it take the form of these rays?" They were looking at the problem using an experiment similar to one commonly done in elementary schools, by making a bed of sand and dropping a steel ball onto it and trying to understand what caused these rays. However, the results did not line up with real world examples, time and time again the sand was scattered in a uniform pattern.

Another chance event ended up bringing a solution to the problem. When scientists undertake experiments, they usually do so in very controlled ways, making sure to test specific ideas and hypotheses. However, on one particular day, the post‐doc had cut a corner and did not completely level out the sand bed used in the experiment, and the irregular, waveform like structure that remained gave the outcome the pair were looking for.

He continued explaining the mechanics behind this, gesturing each step to help us understand, "So, the ball comes and hits the surface, and although sand behaves as a solid when it's not moving, it behaves as a fluid when moving. The ball sends out shock waves inside the sand. When these come to the surface, material is ejected. If the surface is curved down like a valley, it focuses material, and that focusing gives rise to these rays." This can be linked to a wide range of phenomena, as fluid mechanics are applicable in many other areas as well. "It all comes down to fluid mechanics in a sense because it's how things are flowing. In this case, how material that is being crushed and made into a powder is flowing."

Chakraborty has also investigated other examples of fluid mechanics, listing off example after example. Fluid mechanics are widely applicable, and often can be used to explain the phenomena we see around us. "One of the big open questions currently is our understanding of typhoons." He continued, touching on a topic that is very familiar to the residents of Okinawa.

There are many complex processes operating in a typhoon, and due to this an understanding of its underlying mechanisms is quite difficult. "If you look at typhoon/hurricane studies, it's typically theory or simulation, and there are also field observations, but there are no lab experiments." This is because creating a hypothetical 'storm in a teacup' in the lab is not yet feasible, and so observations of these storms in the lab environment has not been done. One of the ongoing projects in Chakraborty's lab is to create an experimental typhoon.

Based on our current understanding, the forecasting of typhoons is typically quite reliable when predicting where they will travel approximately five days before they arrive, however their intensity is still extremely hard to predict. Chakraborty explained that the movement of a typhoon over the ocean shares many similarities with pipe flow dynamics, and that friction at that boundary with the surface of the ocean is one of the keys to understanding how intense a particular typhoon is.

Dr. Chakraborty passionately explained to us a series of inexhaustible examples of issues where a perspective of fluid mechanics is of help in understanding them, such as pipe and volcanic magma flows, typhoon intensities and blood flow in veins or an artificial heart. The extremely deep field of fluid mechanics continues to hold many open questions, and Chakraborty's research at OIST is sure to answer many more of these going into the future.
Video demonstrating the crater ray phenomenon explained to us by Dr. Chakraborty
Provided by OIST

OIST as an ideal research base

When we asked him about how his experience being at OIST has been, Chakraborty answered first about the impacts of being based in Okinawa, "We are geographically a bit isolated and that can create some problems or limitations." In the post‐Covid world, remote work, online meetings and a wide range of electronic solutions have become available. However, this is not a perfect substitute for large departments full of people working on related fields. However, these limitations proved to be something that worked well for Chakraborty.

"This actually turned out to be a huge advantage for me. The geographical isolation allows me to pursue novel ideas without interruption, and if you like risks and if you want to take those kinds of chances, I think OIST is the perfect fit for you." In a traditional, grant‐based environment, pursuing topics and areas of interest would be far more restrictive, as funding may be harder to get and is very results orientated. Because of this, other faculty members and peers may be inclined to give advice based on chasing results, but OISTs unique environment allows for researchers who are more inclined to investigate areas that they are interested in, with the freedom they need to shed light on these types of research topics.

He continued speaking about the other staff and students, "For me, the richness of a university comes from the intellectual diversity of people." Over half of OIST's faculty is made up of foreign nationals, and education and administration are all undertaken in English. This diversity, and the international nature of the institute allow for truly unique ideas and 'richness' to develop. This goes beyond just the nationality of the staff, students and researchers but also in their approaches. Chakraborty elaborated more, sharing that some individuals are more focused on innovation and IP, whereas others have other varied angles of approach. This variation and diversity is one of the many draw points that the university has to offer.

He also touched on the unique funding system at OIST, "Having high trust funding is such a privilege here at OIST." The flexibility that the funding system provides is a huge boon for researchers like Chakraborty, as they give the freedom need to pursue more interesting fields of study. If a researcher is confined by their grants and the types of funding that they are given, then there are many avenues of research and discovery that may be left untouched. The intellectual freedom that high trust funding affords to the researchers of OIST was praised time and time again during our interviews.

The mix of its unique location, the incredibly rich diversity of the staff, and the high trust funding system has allowed for Chakraborty to undertake a wide range of interesting research topics that would not have been possible elsewhere. "It was just that by pure chance that I happened upon OIST and I wanted to take that risk. But yes, I am very happy here and I hope I can continue pursuing interesting problems."

The floor map of Lab 2, where Chakraborty is based. Researchers at OIST are not separated into departments but have neighbors studying very different topics. New cross‐disciplinary research opportunities often pop‐up through chance encounters.

On international brain circulation, and a word to future researchers

As part of his role at OIST, Chakraborty also teaches fluid mechanics classes to graduate students at the university. "I teach a course on fluid mechanics, and typical of OIST, the students are from very different backgrounds." These students are undertaking majors from many different fields, sometimes even completely unrelated to mechanics. As an example, he mentioned that he had taught students who were mathematicians, engineers, material scientists and pure biologists. This diversity allows for the sharing of various viewpoints and bits of knowledge and is something that the university encourages.

OIST runs a system known as 'Research Rotations' where every student gets to experience research in different groups, even when it falls outside of the area of their major, and this circulation of knowledge was emphasized as a very positive point of the institution. In describing how students joined his group, Chakraborty noted "The students came and talked with me about working on fluid mechanics, this was not a part of their original plan at all. They found that they liked fluid mechanics after taking my course and undertaking a research rotation in my group. I thought our chemistry was good and they ended up being my PhD students." The international nature of OIST, the benefits of the circulation of knowledge through research rotations and the ability to do cross disciplinary research with both post‐grads and other professors is a highlight of the university.

When asked to give advice to researchers or students looking to work in Japan, Chakraborty talked about the general impression most people have regarding the country. It is extremely famous as a tourist location, boasting huge numbers of annual tourists pre‐covid (Current numbers are steadily rising, but still down compared to pre‐pandemic figures). However, it is not viewed very highly as a location for further study and work as a researcher. This was where the issue of language popped up, and as English is the working language at OIST, was an area that he had advice. "If you want to target people from outside and want to give them many more options, then I think a key is to really expand the scope of the things available in English, particularly in universities."

Another question is how researchers can advance their career post‐degree in Japan. Referring to a case where one of his talented post‐docs could not obtain the position of an assistant professor in Japan, he suggested that things should be more open to foreign post‐graduates so that they are able to continue to stay and work in academia in Japan. "If the academic system opens from the bottom and some more freedom is given, I think you will really find many people, very talented people coming in."

OIST has a fantastic platform for contributing to this process, and the results that the university has achieved, both as a research institution and in attracting foreign nationals is a potential example to be followed into the future. "Why not take the results of this successful experiment and build on them?" Chakraborty said enthusiastically. While changing traditional methods and viewpoints can be challenging, taking the lessons learned from OIST and using it as an example may be one way to further promote Japan as a research location, and to create more research outcomes in the country.

Dr. Chakraborty's interesting journey ending up doing research at OIST, his rich experiences working with other international colleagues, and the many examples of his success are great examples of why the international circulation of talented people is extremely important in academia and should be further promoted for the future of research in Japan. OIST as a research institute is playing an important role in this, and international, talented researchers like Professor Chakraborty are an invaluable asset in driving successful research results out of research institutes based in Japan.

(Interviewer: Yoshihiro Higuchi, Director for Global Strategic Issues, JST)


Pinaki Chakraborty

Professor, Okinawa Institute of Science and Technology

After graduating from the National Institute of Technology, Surat, India with a Bachelor of Engineering, he moved to the United States and continued his studies at the University of Illinois at Urbana‐Champaign obtaining both a master's degree and PhD. Currently serves as the Principal Investigator of the Fluid Mechanics Unit at OIST

<About OIST>
The Okinawa Institute of Science and Technology (OIST) is a graduate university dedicated to conducting world‐leading research, growing the next generation of scientific leaders, and fostering innovation and sustainable economic growth in Okinawa. Since its founding 11 years ago, OIST has gained recognition in the international scientific community. When normalized for size, the university ranks among the top ten institutes in the world for high‐quality and high‐impact scientific research outputs.

OIST homepage:

Back to list of interviewees

Back to Interviews & Opinions

Interviews & Opinions

Recent Updates

    Most Viewed