Computational Fluid Dynamics (CFD), which is used by a wide range of industries to design their products, can  simulate very complex physics using mathematical techniques.

Sujan Dhar, our next pathbreaker, Sr. Aerospace Software Engineer in the Scientific Computing team at Blue Origin (Seattle) within their Blue Engines unit, works on developing computational tools used to solve complex problems leading to the design of better rocket engines.

Sujan talks to Shyam Krishnamurthy from The Interview Portal about being exposed to extremely complex CFD simulations at Simerics, a small startup that he joined after the completion of his PhD .

For students, many students go into engineering as a default, even though their interests lie elsewhere.  However, if you are someone who truly enjoys something like mechanical, aerospace, civil  engineering etc., there are many career paths which are rewarding  both technically and financially.

Sujan, tell us what were your growing up years like?

I was born in Kolkata, India and due to my dad’s transferable job, grew up all over India.  People are always surprised to hear that I went to ten different schools for my K-12 education  – and they were all over the country, from Angul in Orissa (now Odisha) to Neyveli in Tamil  Nadu, before my family eventually settled in Hyderabad, at that point in Andhra Pradesh. My  dad, now retired, was a Mechanical Engineer and spent his career building thermal power  plants all over the country, and a couple of them in the Middle East as well. My mom had her  master’s degree in philosophy. She was a homemaker and was the primary person  responsible for bringing up me and my younger sister. As far back as I can remember, I always  had an interest in physics and have memories of learning the core concepts of Newtonian  mechanics while doing my physics homework and discussing it with my parents. As far as  extracurriculars in school, I was interested in quizzing, cricket, football and participating in  athletics events.

What did you study?

I did my BE (Hons.) in Mechanical Engineering from BITS – Pilani and followed this up by an  MS in Mechanical and Aerospace Engineering from SUNY Buffalo and finally a PhD in  Mechanical Engineering from Purdue University.

What were some of the influences that led you to such an offbeat, unconventional and uncommon career in Space?

At the completion of my 12th standard, I had scored well enough in the respective exams to  have a shot at going to IIT or BITS-Pilani. My love of physics had only deepened over the years,  and I was quite adamant that I wanted to pursue physics for my undergrad. My dad, being a  mechanical engineer himself, persuaded me to consider mechanical engineering since  many of the fields of physics: mechanics, optics, thermodynamics etc., were also core areas  of mechanical engineering. My IIT-JEE rank was not high enough for mechanical engineering,  but it was my first choice for BITS-Pilani and I was overjoyed to get in.

My first couple of years at BITS-Pilani were somewhat confusing academically. The subjects  were varied, ranging from general biology to measurement techniques, and most seemed  distant from the physics related subjects that I had wanted to study. This all changed in my  second year with the introductory class in fluid mechanics – the study of how liquids and  gases move, and why they behave the way they do. I absolutely loved that class and as the  curriculum progressed, I continued to enjoy the classes which had more of a “physics” flavor  to them such as electromagnetics, heat transfer or materials science. I also did a couple of  projects in the physics department under the guidance of Prof. Gaurav Dar during my  undergrad which were an early introduction to the world of research, and had a couple of  internships under my belt before graduating – at DRDO and at Mercedes-Benz R&D India, both as part of BITS-Pilani’s Practice School program, which sends every student out to work inside a real company for a full semester.

The DRDO project was part of a summer internship and involved a study of thrust vector control mechanisms in rockets – mostly a theoretical study I conducted at the Solid Propulsion Systems Center. The project at Mercedes Benz was a semester long project involving systems level modeling of fuel cells, where I developed a library of components which could be easily connected together to model automotive propulsion systems based on fuel cells.

In particular, I credit my final year internship at  Mercedes-Benz R&D (particularly my mentor Mr. Anand Pitchaikani) for giving me a very early  exposure to the type of applied research possible within industry – aimed at impacting the  development of products which directly benefit society. Having fallen hard for fluid  mechanics, I applied to several universities with strong research programs in fluid  mechanics/heat transfer with the intention to pursue a master’s degree (MS).

Can you tell us about your career path?

While I received admits from many of the universities I applied to, I only received a fully  funded scholarship from a couple. Of these, I chose to go to SUNY Buffalo where I had a  Teaching Assistantship for financial support. This gave me the freedom to explore a couple  of research labs in the general area of fluid mechanics and eventually landed on a research  program and performed my thesis research under the guidance of Prof. Hui Meng at the  Toshiba Stroke Research Center.

A stroke research center is the last place a mechanical engineering student expects to end  up, but the lab studied how blood flows through the arteries of the brain – and blood moving  through a blood vessel follows exactly the same laws of fluid mechanics as fuel moving  through a pipe or air moving over a wing. Understanding those flow patterns helps doctors  understand why aneurysms form and rupture in some patients and not others. An aneurysm is a bulge in the wall of an artery. Aneurysms form when there’s a weak area in the artery wall. Untreated aneurysms can burst open, leading to internal bleeding. They can also cause blood clots that block the flow of blood in your artery. Depending on the location of the aneurysm, a rupture or clot can be life-threatening.

It was my first  real lesson that fluid mechanics is not one industry you get locked into; it is more like a  language, and it turns up wherever something flows.

It was here that I was introduced to computational fluid dynamics (CFD) – which would set  me on the career path I am on to the present day. In simple terms, CFD means using a  computer to predict how air, water, blood or fuel will move through a design, and how heat  will travel with it, so that engineers can test an idea on a screen before anyone spends money  building a real prototype that might break. I worked closely under the supervision of a post doc within the lab Dr. Markus Tremmel, who had a big influence on the manner in which I  approached problems, and in general was a great early role model in my career.

After my masters, I decided to return to India for a couple of years for personal reasons and  applied for a few R&D roles within industry (my contacts from my internships and from BITS Pilani helped) and received a couple of offers. I eventually joined General Motors Technical  Center India as a CFD Engineer within the Methods and Thermo-fluids team. What attracted  me was the mission of this team: to develop novel simulation methods which would then be  used by GM’s production engineering teams to improve and design products. This job gave  me exposure to cutting edge research and product development using CFD within industry, and I received an incredible education in the commercial CFD software that industry actually  runs on, such as Ansys Fluent, Star-CCM+ and Simerics. I was able to work on research  problems such as fuel cells and visit GM’s fuel cell lab in upstate New York and drive a fuel  cell vehicle!

While working at GM, I realized that there existed an entire industry of computational physics  software tools which are used by a wide range of industries to design their products. While I  could use such tools within GM, I wanted to be able to develop such tools – which can  simulate very complex physics using mathematical techniques such as numerical methods  and linear algebra. My drive to learn more about these techniques and to start developing  such tools led me to apply for my PhD.

So, I applied to a few schools with strong computational fluid dynamics programs within the  US and again received a few admits, this time each one came with research funding which  would cover my tuition as well as provide me with a salary (PhD student salaries are meagre,  but enough to live on comfortably in a university setting). This time I chose to accept the offer  from Purdue University for a PhD in Mechanical Engineering. My decision was driven by  Purdue’s stellar reputation as an engineering school (consistently ranked in the top 10 within  the US), the fact that Neil Armstrong, one of my childhood heroes, went to school there, and  most importantly the research I was going to perform.

My advisor at Purdue was Prof. Andrea  Vacca at Maha Fluid Power Research Center (“Maha lab”) and I was one of his first students  as a new professor at Purdue. We talked and exchanged quite a few emails while I was in  India, and I had a solid idea of the research I was going to be performing and was able to get  a head start. During my PhD, I worked on developing a cutting-edge computational physics  tool using OpenFOAM, an open-source computational library – open-source means the  code is free for anybody in the world to read, use and build on, and any student reading this  could download it today. My research was fully funded via industry grants, and in general  Maha lab has a very strong support base from industry partners. The experience during my  PhD only strengthened my interest in developing computational tools which are directly  used to drive the design of products within industry.

The computational physics methods and tools I worked on developing during my PhD was used to simulate and drive the design of positive displacement machines by several companies (Casappa, Caterpillar, Bosch Rexroth, Danfoss etc…) and continues to be developed at Maha lab and supports industrial design to this day – something that is a source of great satisfaction (and some pride) to me.

After the completion of my PhD in 2014, I received an offer from Simerics – a small  company/startup developing an innovative and cutting-edge simulation tool called  PumpLinx. I had been exposed to PumpLinx both at GM as well as during my PhD, and I was  amazed at the tool’s capability to perform extremely complex CFD simulations, and  therefore, jumped at the opportunity to join the company as one of its first external hires for  the development team.

Simerics develops a 3D engineering simulation tool called Simerics-MP+ (formerly PumpLinx), which can be used to simulate fluid dynamics, heat transfer, acoustics, structures and many other physics. It is widely used in the fluid power, automotive, aerospace and oil and gas industries with Danfoss, Toyota and Safran as a few examples of the many companies which rely on this tool to design their products. At Simerics, I had the opportunity to apply the skills I had learnt over my PhD to develop a tool widely used within the industry.

I worked there for over a decade reporting directly to the founder and  president of the company. Being a small company, I was exposed to a wide range of functions  apart from my core job of developing the computational software – customer support, pre-sales, customer presentations, representing the company at conferences – and had the  opportunity to work with (and learn from) some of the pioneers of the CFD industry.

How did you get your 1st break?

I would say my first “break” to a career in computational physics software development was  my PhD thesis work at Purdue which provided me with valuable experience in developing  computational tools which were directly funded and used by industry. The second “break”  was the developer role at Simerics, since this was the first time I was working at the  intersection of mechanical engineering and computational physics.

The decade after 2014 happened to be a time of great renaissance in the space industry  leading to the birth of what has been called the “new golden age of space exploration”. At the  end of 2024, I received an opportunity to join a small team within Blue Origin developing  computational physics tools which are used to design and improve Blue’s rocket engines.  This was an incredible opportunity to use my skills to directly contribute to this new golden  age, and it also aligned with a lifelong passion for space exploration and rockets. I accepted  the position, and I currently am a Sr. Aerospace Software Engineer in the Scientific  Computing team within Blue Engines – working on researching and developing physics based simulation tools on a variety of domains (fluid mechanics, heat transfer, acoustics,  combustion) which are used to design Blue Origin’s rocket engines.

What were some of the challenges you faced? How did you address them?

One of the bigger challenges as a mechanical engineer by training, was to  be able to establish myself as a successful computational software developer. While I had  formal training on the mathematical and physics side of the role, I did not have much formal  training on the computer engineering side. This is where my time at Simerics was truly invaluable – learning on the job to develop a cutting edge CFD tool which companies such as Ford, Toyota, GM etc. depend on for their product development. The  primary way I addressed this was to learn the more software engineering-oriented parts of  the job by observing and then following the practices of the more experienced software  engineers within the company – reading really well written code can be very educational!

Where are you working currently?

As I mentioned in a prior answer, I’m currently a Sr. Aerospace Software Engineer in the  Scientific Computing team within the Blue Engines business unit of Blue Origin. The role  requires knowledge of the physics being modeled, numerical methods and computational  software development.

What is a typical day like?

My typical day will typically be working on problems where the  current modeling tools for rocket engines fall short, researching the relevant physics and  numerical methods, working on implementing the methods in a software tool and validating the tool against experimental data – that is, checking that what my software predicted  actually matches what happened when a real engine was tested. I enjoy every part of the job,  including working closely with designers and engineers who are responsible for designing  and manufacturing rocket engines. Working on developing computational tools used to  solve complex problems leading to the design of better rocket engines – what’s not to love!?

How does your work benefit society?

I believe deeply in Blue Origin’s mission and more broadly, in the benefits of space  exploration. As the climate challenges facing our planet have come into sharper focus over  the years, I strongly believe that moving heavy industries to space gives humanity the best  opportunity to continue to accelerate its pace of progress. Exploration is a core part of human DNA, and we are constantly inspired by the stories of travelers and pioneers such as  Marco Polo, Vasco da Gama and Neil Armstrong – and I feel proud to be able to contribute to  humanity’s ability to explore the stars.

Any memorable projects?

One of my favorite projects took a simulation that used to run for days – sometimes weeks – and brought it down to a few hours.

While at Simerics, I developed what we called a mixed-timescale heat transfer modeling  algorithm, which lets the fast heat transfer processes and the slow heat transfer processes  each be handled on their own natural timescale within the same simulation. The work was  driven by a fundamental physics insight, and it made accurate and efficient simulations  possible for products such as electric motors, engine pistons, ball bearing assemblies and many others. When a simulation goes from weeks to hours, it stops being something an  engineer runs once at the end to check their work and becomes something they can run  every day while they are still designing – and that changes how the product gets designed.

Your advice to students?

Well, I am sure students have heard things like “follow your passion” etc., and I absolutely second that, particularly while choosing to do a PhD in any field. Something I have noticed  generally, is that many of the brightest students in engineering in India give up engineering and go into management by doing an MBA shortly after engineering – and this is fine, because  many students go into engineering as a default, even though their interests lie elsewhere.  However, if you are someone who truly enjoys something like mechanical, aerospace, civil  engineering etc. I want to let you know that there can be career paths which are rewarding  both technically and financially. Hopefully my own career serves as an example of this, and there are many other examples. This is where Interview Portal is an excellent initiative, where  students can see all the various paths people have followed successfully.

Future plans?

While the use of computational simulation in industrial design has progressed by leaps and  bounds, there is still a long way to go. I hope to continue to develop better, more accurate  and more robust simulation methods and tools which would relentlessly move industrial  design processes away from trial and error, and towards one based on physical  understanding.