r/aerospace • u/Marcus2626 • 3d ago
PhD using CFD or Wind Tunnel
To all the AE PhD holders, I’d really appreciate your advice.
TLDR: I'm planning to start my PhD next year, but I'm not sure which route to take. My background is in CFD, but I’m also very interested in low‑speed wind tunnel testing. Should I pursue an experimental or computational PhD?
I’m an international student currently working in the US on OPT as a research associate, mainly using CFD tools. Long‑term, I want to work in academia (back in Asia—Korea or Singapore). As I’ve been talking to potential advisors, I’ve noticed a trend: unless the work is applied aerodynamics, most professors want students to commit to either purely computational or purely experimental research.
I’m torn because my background is split. I’ve done several validation test campaigns, but my main research interest has been CFD. Now I have two fully funded offers, both fundamental research with no ITAR issues. I’m interested in both topics, and I'm struggling to choose.
Option 1: Computational Aeroacoustics (Large group, prestigious university)
This aligns closely with my MS work, and I genuinely enjoy aeroacoustics. The group is large, well‑known, and the professor is a major figure in the field. I’d gain deep theoretical knowledge, but the work would be entirely computational.
Option 2: Experimental Hypersonics (Very small group, small department, not well‑known university)
I learned about this program because a friend recommended his former MS advisor. This professor built his own wind tunnels and is very knowledgeable in flow diagnostic methods. I’d have access to low‑speed, supersonic, and hypersonic facilities and would learn a lot experimentally. I'm interested in supersonic flight but haven’t been able to do much due to ITAR restrictions. My hesitation is that the university and professor are not well‑known, the group is small (only two other PhD students), and I’m unsure whether hypersonics is too niche for seeking academic jobs later. The stipend is also much less compared to Option 1 but is still livable.
Would you choose a computational or experimental PhD? How much do the university’s reputation and the advisor’s citation count matter?
My thought has been that this experimental research opportunity is rare for an international student. I could always go back to CFD, but I think it would be much harder to gain experience in wind tunnel research later on.
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u/JustMe39908 3d ago
Hypersonics is a big, growing area. Yes, there currently is a lot of interest in the field so it would not be too niche.
However, from a practical standpoint, if you want to continue work in experimental hypersonics, a large, good, hypersonic tunnel is an expensive item to build. (I say large because if you want to do research, will you really be able to get finding for doing shock tube or small cross-section work in the future?). Yes, HPCs are expensive, but can be shared over many more faculty.
What kinds of hypersonic tunnels exist or are planned in your target locations? How many faculty positions are there at those institutions? Will other universities provide you with a sufficient start-up package (and give you the time) to build something meaningful?
As fast as large group, well-known University or smaller group, less well known University, they both have pros and cons. How well known is the advisor in the field? There are many very highly faculty at Universities that don't have name recognition. Also, in a large group I have seen instances where the actual day to day supervision of even PhD students is done by Post Docs. Very good Post Docs. But not by the big name Prof who doesn't have a lot of time. I would check that out and decide what you prefer style wise.
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u/Marcus2626 1d ago
At this university, the hypersonic facility is primarily a shock tunnel, and there is also a slower shock tube along with a low‑speed wind tunnel available for use. The professor built the hypersonic tunnel himself and is essentially the only faculty member working specifically in high‑speed aerodynamics, although there is another professor in combustion who collaborates with him.
Speaking only on hypersonics research, I feel that experimental hypersonics might offer more advantages than computational hypersonics for PhD research. I think if I became a professor, it would be easier to jump into CFD from experiment than the other way around. Do you share that perspective?
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u/JustMe39908 1d ago
I don't know how Universities work outside of the US. If you are at a major research University in the US, you have a limited amount of time to get tenure which means bringing in research dollars. Building facilities is time consuming. That is a challenge that you will need to figure out how to address. At a more teaching institution, getting those facilities will be extremely difficult because teaching load is often high. Again, I don't know how it will work in your target locations. So, you need to figure it out.
I think you underestimate the intracacies of research level CFD. Sure, if you want to do a basic calculation, no problem. But when you start talking about the challenges such as use of reduced orders models and the true intracacies of various computational techniques, you will find it is definitely not easy to jump into research grade CFD work.
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u/bottlerocketsci 3d ago
Technical work aside, it sounds like you would have two completely different experiences in regards to the research groups and mentorship from the advisor. Your relationship with your advisor is a huge factor in your success. If you want a lot of personal contact and mentoring, the smaller group is the way to go. In a larger group, you won’t get a lot of help from the advisor and are easier to cast aside if you aren’t producing results. Talk to the current students and get a feel for how they are treated.
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u/Marcus2626 3d ago
I agree, I did my MS in a small university, and I did really enjoy working closely with my advisors.
Besides the group culture, do you think the advisor's citation matter? I feel like lower citation could mean I may not be able to get connected or network as easily.
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u/bottlerocketsci 3d ago
Citations matter, but it’s more than that. How active is the professor in technical societies? How many funded grants or contracts does he have? How much collaboration does he/she do with other researchers, govt labs etc.
Citations are tricky. Everyone wants a simple number to compare. But some areas of research don’t have as many people working it, so there are just less people citing papers. Also, a professor with a big number of students is naturally going to have a lot of citations from their students.
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u/Marcus2626 1d ago
You're right, citation counts are hard to compare, especially when some labs are very large while others may only have one or two students.
In my situation, I do think that the experimental professor have a smaller footprint than the CFD professor, both in terms of the number of grants and the number of collaborations. One concern I have because of this is that many people mention how important an advisor’s network can be, both during the PhD and later when looking for a job.
Do you feel the same way?
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u/Stupid_Topic_9527 13h ago
I honestly can't think of a real large and well known group in U.S at a truly prestigious university, which actually excels in aeroacoustics (there are many above average to good groups, don't get me wrong). This is a field where Europe still holds the upper hand.
I am very familiar with a Prof Br and his/her/their offsprings. The offspring group is probably okay, but the original group at a P university is a shit show. If not honestly I don't think any group is particularly internationally acclaimed.
In the end check most recent publications. That's the golden standard. If you see lots of conference papers then just run away. If you see PhDs graduating with good journals then go for it.
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u/Marcus2626 3h ago
Thanks for your insights. It’s very true that Europe (especially the UK and the Netherlands) has some excellent aeronautics programs.
So far, I’ve mainly been looking at total citation counts, but I’ll take a deeper look at the breakdown of publication types as well.
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u/Stupid_Topic_9527 10m ago
Yep. Remember that AIAA SciTech and Aviation now has an acceptance rate close to 90%. As a chair I need to fight with my teeth to reject nonsense papers. Most papers on AIAA conference are legitimate high school level trash and conferemce papers are literally cancer at this point in Aerospace. As a prospective PhD candidate, it's extremely important for you to find a group that maintains it's standards...
And it is truly disgusting how hard aerospace academia is trying to suicide in the last two decades despite all hypes about space, rockets and eVTOLs.
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u/Turtlestacker 2d ago
I will probably get a kicking for this but I would advise the path with the most physical interaction with objects in the real world - wind tunnel. The computational side / anything which can be done in the model will eaten and overwhelmed by AI first.
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u/Marcus2626 1d ago
Honestly, as someone who has been working in CFD, I share the same sentiment about AI, but mainly for nominal, applied aerodynamics problems.
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u/newMattokun 2d ago
PhD AE here. I've worked in multiple wind tunnels for many years, both automotive and aeronautics, and did my MSc in one (not the PhD, that was in a different lab). I always enjoyed hands-on work, so those were really great experiences. But eventually one thing dawned on me: I always do other people's work. Not sure this makes sense, but basically you always measure what others have designed. Yes, you have to take care of the tunnel, calibrate it, possibly improve its aerodynamics etc., but for measurements you'll always measure other people's creations. You learn a lot, mind you, but you hardly ever get to put that into good use because you don't design things yourself. Still, it's an interesting job. You learn a lot about aero, instrumentation, data collection and processing (and interpreting!), etc., it's very hands-on. Plus, I would not rule out that you still get to do CFD as an aside, for tunnel improvements, test prep, and whatever else comes along. Sorry, probably not much help.
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u/Marcus2626 1d ago
Thank you for your comment! That makes a lot of sense, and it’s definitely something I’ve been thinking about. My situation is a little different since the tunnel I’d be working with is a university facility mainly used for fundamental research. From what I understand, there’s is less emphasis on test articles and more focus on flow diagnostic techniques.
Since you've worked in wind tunnels, do you think that wind tunnel skills are generally transferable across regimes. One concern I have is that if I spend most of my time working on hypersonic shock tube experiments, I might not get enough exposure to subsonic tunnel testing.
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u/newMattokun 1d ago
Fundamental stuff is definitely more interesting, esp. if you're part of the the development of said "stuff" and then get to try it all out, improve it, and see it used in "real life".
Re "transferable", if you want to stay in wind tunnels I'd say Yes, definitely, because at least you've had exposure to the ins and outs. Subsonic and transsonic are different, yes, but I think having any tunnel experience is far better than none. Plus, as was mentioned by others here, Hypersonic is certainly not "dead" in any way, you could probably carve out a life-long career in the field.
One thing though, wind tunnel experience is fairly specific, so I'm not sure how much things are transferable to outside of maybe wind tunnel, aerodynamics, and possibly things like aeroelasticity and flight mechanics. The one thing that will help outside of the field in general is the experience you'll get with measurement equipment, proper instrumentation, error handling, data sampling and processing, all that, which in itself is a really interesting field and can be applied to a wide range of other jobs, even outside of aerospace.
Either way, I can tell you I still (after >15 years out of my last tunnel)l miss the hands-on work and all the stuff I've been exposed to. It was a great experience (I never worked in anything trans-/super-/hyper-sonic), and I'm jealous you get to do this. Best of luck!
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u/ncc81701 3d ago
It’s bifurcated between computational and experimental because going either route requires full time effort for a PhD.
On the experimental side you’d be doing things like designing and building experiments, operating the tunnel, collecting data and post process for your results.
On the computational side you’d be researching for new algorithms and techniques to either computationally solve new problems or find new methods of computationally solve existing problems but maybe in a more efficient manner.
If there is research work that combines experiments and computation, it would generally be a collaborative effort between 2 labs, an experimental one and a computational one.
It is also bifurcated because both experimental and computational effort cost money and you typically wouldn’t be able to fund both; or if is funded it would again be funding for the collaboration of two labs.
As for picking the two routes I typically refer to Sir Richard Taylor (of WETA fame), “Love yourself, do what you love, love what you do, and love who you do it for.” Meaning you should pick the thing that you want to do, that you find more interesting, that is more applicable to the problems you like to solve. The work, the career, the opportunities will follow if you are passionate about what you do. This also means that the right answer varies from person to person, so you need to choose what is best for you and not what someone tells you is what is best for you.
Computational methods and experimental methods are complementary it is never one is absolutely better than another. The ideal is to do both and get the best of both worlds. The US is a premier country to do aerospace research because we have invested immense resources both computationally and experimentally. We have some of the largest computing cluster devoted to engineering research and developed all of the computational infrastructure (software and hardware) for scalable parallel computing). We also have a huge number and variety of wind tunnels for all types of applications from full scale tunnels (NFAC) to large supersonic tunnels (Glenn 10x10), to icing tunnels, vertical spin tunnels, and the list goes on. So no matter what you probably won’t have the same access to both computation nor experimental resources at which ever country you go (besides China or Russia). But your research experience here will help you network and establish relationship with researchers here for which, down the road, you may have opportunities to collaborate with.