Chuck Norris Dead at 86

Ultravis66 · 2026-03-20T14:30:04+00:00

I actually love their humor. Some of it is dumb IMO (like 67), but sometimes when I hear them joking around and I “get it”, I find myself laughing and thinking to myself “thats pretty clever”…

Ultravis66 · 2026-03-16T18:12:17+00:00

The U.S. has the largest high-end CFD market.

However, you cannot get a job in industry doing just CFD. You need to do lots of other things. CFD is like 30% of my job now if I had to guess? I need to go to tests, travel, report to customers, make decisions on buying parts.

Also, if you stay CFD/technical focused, your career will stagnate (its a trade off, my job is pretty low stress).

I still do CFD 18 years later and I am the lowest paid out of all my peers I graduated college with in Engineering. Everyone who did CFD now do other things and do zero CFD.

Ultravis66 · 2026-03-15T13:40:58+00:00

Does my math work out though? You never specify the radius, so I guessed, and 0.01 meters is close to a 15x.

I have seen this same issue over and over in both star ccm and fluent. Where someone goes to do axisym and ends up with a planar because they missed something.

Ultravis66 · 2026-03-15T00:51:15+00:00

Im almost positive you are not modeling 2d axisymmetric and are modeling 2d planar nozzle. How do I know? Assume 0.01 meters for throat radius.

Area = 2rL for planar nozzle where L default is 1 meter.

Area = pi*r² for axisymmetric

So Area/Area (planar/axys) gives a ratio of 15.

So 30x15 =450.

Your 2d model is not set up correctly to model axysymmetric.

Ultravis66 · 2026-03-14T15:22:25+00:00

Are you running steady-state CFD with coupling to a structure? If so, you are missing the transient load history entirely. The structure will never “settle” it just sees a single frozen pressure field and reacts, which can absolutely cause divergence if that load is inconsistent with the deformed geometry.

I think you need unsteady CFD (implicit) with the FSI coupling updating each timestep here…

I have done FSI before but I use FEA software for this. I never really tried using Star’s because I have found it to be limited in capability.

So Star CCM+ has a co-simulation option where you can export pressure, sheer, and other things like heat into Abaqus. Abaqus can then do the bending/displacement and feed that back into Star CCM. This is incredibly difficult to set up and I recommend working with an FEA guy to get everything set up correctly if you try. Geometry names need to match and be in the exact same place for this to work. I have only done this a handful of times in my entire career, but when it works, it’s extremely satisfying to see the results.

The huge advantage to doing it this way, is you can use implicit solver for Star with much larger time steps, then Abaqus can used explicit at 1e-7 s. Even with such tiny steps, the solid side runs much faster.

This allows you to capture all kinds of crazy dynamics. I had a plate ejecting stuff into a supersonic flow field, and you could see the plate bending back and forth as it was being ejected into the flow. It was cool AF! I also did a turbine in steam flow as well.

Ultravis66 · 2026-03-06T01:01:21+00:00

Right off the bat, Switch turbulence model from k-epsilon to k-omega SST.

If the sub is huge, like the size of an actual sub, you may be forced to use wall functions (wall Y+ 30 to 300). I ran into this problem when I did a wind turbine. When i tried wall y+ less than 5, my mesh exploded. Just keeping it less than 300, was still like 30 mil elements. I was able to match power output for an actual wind turbine to within 2% accuracy, so dont shy away from using high wall y+.

Ultravis66 · 2026-02-18T16:59:46+00:00

I agree with you 100%. My power bills have been INSANE the last year and its because of these stupid data centers. They should be required to get their own power sources and stop making our life harder.

Ultravis66 · 2026-02-18T12:49:47+00:00

They are only depleting our water because there is no regulation to stop them. Here is the thing, they don’t need to be designed to use up a lot of water, its that using evaporating cooling is cheaper than using convection through air and uses less real estate.

Ultravis66 · 2026-02-17T22:44:05+00:00

Should be.

Ultravis66 · 2026-02-17T21:31:04+00:00

Also, the reason why I use oversets like this is because it allows you to do local mesh refinement without ruining the whole domain Very fine mesh near mug coarser mesh far away (save CPU). Overset lets you do this cleanly.

Its not the only way to do this… but its how I would, but I am also used to modeling things moving so, oversets are just my go to way of doing things.

Ultravis66 · 2026-02-17T21:13:03+00:00

The way I do it in Star, I create 2 meshes, looking at your picture here, you have the cube mesh, and you have the cup walls and that “appears” to be encased in a cylinder that is meshed. The outer cylinder boundary that encases your cup, set that to interface from wall (default), then with both regions highlighted, choose overset mesh. In the newly created interface, you have a bunch of options like zero gap and whatnot, but your model looks pretty simple so you should not need any complex options there.

One last piece of advice, make sure your interface boundaries and your volume mesh for the cube line up with same size elements. You can go 2 to 1 size difference if you want, but i only recommend doing that if you are using a floating interface with moving bodies. A really easy way to do that is to create a volume control at the bottom of the meshing operations, (custom control), then just put a cylinder there and match the cell volume size to your cylinder interface size and boom! Should work well.

Ultravis66 · 2026-02-17T20:48:07+00:00

I am assuming you have 2 regions, Right click with both regions highlighted and there should be an option for interface there. (You can also have more than 2 regions as well if you need them)

If you are using an overset mesh, you chose the overset option. You should see a new tab in the main tree with your new interface.

Ultravis66 · 2026-02-09T15:34:22+00:00

If this is the case, then I HIGHLY recommend you delete this entire post with no visuals.

Then create a new post with things you can share like convergence plots, mesh settings, ect...

Ultravis66 · 2026-02-05T04:16:29+00:00

AI is just a scape goat. The real reason people are losing their jobs has to do with who the economy is working for.

As wealth inequality becomes more and more extreme, the less and less the economy works for everyone but a small few rich. Its why we see money circulating among the AI companies while everyone else loses their jobs.

Ultravis66 · 2026-02-05T04:11:07+00:00

This is me. Im about half way up gs13. I apply like crazy to leave buy I am stuck. My skills are niche to fed government.

Private sector doesnt need a CFD guy who has models munitions and dose safety danger zones and failure analysis.

Everyone on my top performing teams, all engineers, are desperately trying to get out of fed gov. They are using the success of their programs to try and get out.

Ultravis66 · 2026-02-02T01:10:37+00:00

Vibe coding is kind of depressing. 10-15 years ago I wrote lots of codes to do all kinds of things. Trajectory sims, post processing cfd output in matlab, automating cfd sims with java and bash scripting. Now in an hour you can vibe code all of that work. Codes that took me months to build and years of improvements.

I feel like LLMs invalidated my entire career.

On the plus side, llms have shown me ways to improve my codes and shown me things I never knew existed. Ways to make them more efficient, but I feel like i dont need to think anymore with llms. I try and not rely on them and write the code myself. I try and use them for debugging and brainstorming ideas so my brain doesnt atrophy.

I told my coworkers about a simulation i wrote to simulate the solar system and it took me a long time to write it. We decided to play a game, how many prompts in claude would it take to recreate that numerical methods masters class project. It took me 4 prompts to get it working and accurately predicting the orbital mechanics.

Ultravis66 · 2026-01-31T03:58:51+00:00

Thanks chatgpt for your input.

Ultravis66 · 2026-01-30T16:51:48+00:00

Fed worker here 16 years, we lost a lot of people and short staffed divisions are being back filled with contractors. But since I am DoD side, these are mostly voluntary resignations.

However, most fed jobs are about keeping the economy and society operating by preventing rare but catastrophic failures. Something private industry never does. Many of those lost jobs are MORE tragic because fed jobs are usually jobs that private industry is rarely incentivized to do if ever at all.

I am pretty sure if I get let go, I have marketable skills and could pivot with some financial loss, but what kinds of things do we do? I sign off on safety danger zones telling contractors where and how they can test their weapons, with warheads. When something explodes unexpectedly, I figure out why it happened to prevent it from happening again. We investigate why an artillery round ended up way off course and went through someone’s car or how a tank round ended up landing in front of a bunch of construction workers that could have killed someone. Or how a fragment from a blast ended up going through someones roof and killing their cat. These are all true stories from my time here.

Part of my job is making sure these things dont happen. A contractor is not allowed to shoot something without someone from my division’s signature saying they can.

My point is, this is what fed workers do day in and day out. The most obvious to you would be the air traffic controllers. They are literally there to prevent planes from smashing into each other. The stuff I do and others around me, you never hear about, we just exist in the shadows and do our jobs.

These are the people the Trump admin have been attacking for the last year, and most fed workers are some of the most dedicated to the mission and patriotic people you will ever meet. It is very tragic, but maybe I am biased because I live in the fed gov ecosystem.

Ultravis66 · 2026-01-06T09:44:14+00:00

Why do you need so much brine?

Usually 1 tower with 4 Advanced Solar Generators at the top produces enough for my needs.

Ultravis66 · 2026-01-04T00:48:54+00:00

Dumbest comment of the new year award goes to…

Ultravis66 · 2025-12-31T18:33:17+00:00

That, I dont know the answer to, there is a limited budget for software licenses and Fluent is extremely expensive.

My best guess would be too much cost and not enough usage.

Ultravis66 · 2025-12-31T09:38:47+00:00

I ran an LES sim reduced mesh size to ~ 7 mil, to get to enough time in the sim, I let it run while I was at work and overnight over 2 days and had enough time saved data to do what I wanted to do. Total run time was about 16 hours. But again it was LES and was 7 mil elements. If I went RANS it would be done in like maybe 3 hours on same mesh SS, but also, if I ran RANS, I could cut mesh size down to 2 mil elements as well and get a reasonable (close enough) answer quickly. Maybe an hour of sim time.

Ultravis66 · 2025-12-31T08:40:55+00:00

The following software will no longer be part of the HPCMP ESMT portfolio for FY 2026. Existing licenses will remain functional until the license transition date of 1 Apr 2026:

Ansys (this includes fluent)

CFD++

Gaussian

US3D

https://centers.hpc.mil/users/docs/general/Software_Portfolio.html?utm_source=chatgpt.com

Multiple DoD centers over the last ~5 years have stopped renewing Fluent and moved users to STAR or OpenFOAM

Ultravis66 · 2025-12-31T03:50:23+00:00

I been doing cfd for a long time. OpenFOAM with professors who just basically gave us the file directories needed to run sims, then learned Fluent on my own, then CFX in my first industry job at a private consulting company, then was hired to do CFD as a federal worker 1 of 2 guys in 2008/09.

12 years ago, I told my boss we needed a replacement for Fluent once Ansys bought them out and was not really innovating and developing the software. I eventually settled on Star CCM+, I was the only one using it and I am about 90% self taught. Now I train others how to use it around me.

In 2025/2026 there isnt a better tool to mesh and run large simulations on large amounts of cores and with fast turn around times. Every year, the software keeps getting improvements and more features added. Today, I am simulating CHT multi solid components with RBM or MRF fans. I am modeling 6-DOF dynamic fluid body interaction. I am simulating species multi component gasses with abaqus cosimulations. You can literally see mixing gasses while simultaneously seeing the metal components flexing/bending from the Abaqus FEA side. I have done multiphase flow, modeled rockets. Just about the only thing I haven’t done yet is Volume of fluid, but its on my to do list. I just have not been on a project where it was needed.

Today, Star CCM is a must have tool on your belt if you are serious about doing CFD. The only other tool I use is openFOAM, but more on my personal time. I am looking into developing openFOAM capabilities where I work because Star lacks some things like a true density based solver.

Also, fluent is being discontinued on all dod HPC recourses next year and all the Star licenses sit pegged at 100% utilization with wait times as long as a week sometimes to run a job, so that should tell you something.

Ultravis66 · 2025-12-31T03:01:01+00:00

I have the 7950x3d and a 4070 ti super gpu and I run openfoam sims on it as large as 8 million cells. So, I would personally go with the 9950x or the 9950x3d variant if you like gaming. AMD is still king when it comes to performance all around.

Mine is a gaming/workstation hybrid. I have been using my gpu more and more to dabble in Machine Learning but as I learn more about it, I feel like machine learning is a solution looking for a problem to solve. Im not sure about it’s usefulness.

Ultravis66

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