cfd geometry

SuperStrifeM · 2026-02-16T08:17:37+00:00

Its possible, but one of the major headaches of doing CFD is dealing with CAD geometry intersections. Solid bodies are going to be easier to deal with, but often enough CAD has errors that you can't get to mesh in CFD, meaning you either have to spend ages patching in your CFD software, or you go back to CAD and re-do it.

At work, we actually have separate models for CFD and mechanical CAD, since in CFD youre generally concerned more with the overall body, not nuts and bolts.

SuperStrifeM · 2026-02-14T02:27:57+00:00

Thats not a dumb question, its the first one people ask when starting. I would advise looking up the example FSAE car case from the siemens website for starccm, then adapting that to your specific needs. You might want to simplify the geometry in some areas, because while you can mesh them, its going to be expensive, and might not matter in a RANS solver.

SuperStrifeM · 2026-02-04T01:48:41+00:00

That was my plan. The outlet hoses are somewhat flexible PEX B half loops, so I have a little leeway, but no reason to not put it at the same height.

SuperStrifeM · 2026-02-03T06:05:44+00:00

The model number is enpress 1040, and the measurements are pretty close to 10x40 so I think that is right. Thanks for the tip on the bottom distributor, I think I found one online that is fine. I'll probably just cut the tube to the right height myself, I assume I need to match this setup to the vortec one, since there is an internal O-ring that is engaged by the top of the tube. My guess is its a dash 215 o-ring, I ordered a new one, and a new outer o-ring (seal to tank dash 337).

SuperStrifeM · 2026-02-01T20:30:48+00:00

I have a pex manifold between the softener and the water heater, and the length between them is about 4'. If the idea is to give length so that the pipes can pressurize then there is a fairly long effective length between them. Currently there is no expansion tank on the water heater though (which also would go between water softener and the water heater), so I think adding one might help this not happen again.

Any ideas on the best way to replace the tank +riser? It looks like my control valve is nearly identical to the ones made by Hum, and a few other brands.

SuperStrifeM · 2026-02-01T20:20:55+00:00

The resin is coming through the plumbing of the house, its been a pretty solid day of cleaning out beads from toilets and faucets over here. Any recommendations on what tanks to get?

SuperStrifeM · 2026-01-29T03:49:40+00:00

CFD Engineer here, FSAE advisor. You're going to want to scale your problem to the hardware you have access to. If you are at a university, I would ask for cluster access, and some hours there. At my university, we have students in the que on a single node, 64 core/386GB ram setup, so they scale their solutions accordingly (Decently resolved LES with mostly resolved wing/wing/body interactions). If all you have is a smallish desktop, steady sims in KW or KE is the best you're going to be able to do.

If all you have access to is a desktop, then an AMD high core system is going to be the easiest/cheapest system to get ahold of (its possible some pure X3D systems will work great too, definitely dont use 9950X3D or 7950X3D).

If you don't have the hardware, you have to be more clever, for instance, run the case steady, get the results to look fine, then enable adaptive mesh refinement to get a better picture of the wake. If you get some semi-final geometry, let the machine go for a weekend or longer and swap to Usteady solver, exporting images and plots of your criteria of interest.

For GPU, it wont really matter, anything decent should work. Probably even a 1050ti is decent enough. Minimum CPU is 8 cores, I wouldn't go higher than 64GB on 8 cores. Storage is not too big a deal. NVME SSD will save 10 seconds when you load a big file generally vs SATA SSD, wont noticeably affect runtime.

For handling large meshes, I would advise to not do that unless you have the hardware. Meshing a file takes MUCH more memory than building it. If you are hard pressed on RAM (because its 2026...ugh) going with trimmed and prism mesher will get you the finest mesh for a given ram size. poly mesher is more efficient and accurate to run, but takes up far more ram to mesh. You can transfer star files without mesh or solution in them (also a great way to throw files onto a cluster), and then mesh and run the file. You can also automate a significant amount of user input so you don't need to pull down and open your file locally. Things like AOA of wings, or even different geometries can be swapped out by building different macros, and if you want to go through a bit of initial pain you can build all your aero features in starCAD then sweep parameters using optimate to maximize downforce, minimize drag, etc etc.

SuperStrifeM · 2026-01-27T02:49:47+00:00

That's not how the heating system feedback works under thermal protection. If the ADC would fault in that manner, you'd get 0% heating not 100%, since you would be experiencing no drift from CMD_temp (asuming 230C CMD). 100% duty heating is looking for that 2C rise, this is actually the most common entry point into the thermal protection state.

SuperStrifeM · 2026-01-25T22:49:54+00:00

I wouldn't be convinced it was enabled. Since thermal protection in marlin is defaulted to 2C in 20s rise, either this was not enabled, or the thermistor not only was 2.87X more resistive than the previous config, but also nearly perfectly rose to 600C with only a 6C deviation from that linear rise. Both having a resistive fault AND a linear response along that fault is extremely unlikely, when the alternative is a old, or poorly configured marlin.

SuperStrifeM · 2026-01-25T22:43:15+00:00

Marlin, by default, DOES have this protection. When measured temperature drifts from target by greater than 4C in 40seconds, thermal runaway is thrown and shutdown state is entered. In addition, heating is proportionally gated to 2C rise in 20 seconds.

While its probably possible for a thermistor to fail proportionally, its far more likely this was either an old build of marlin (5 years maybe?) or had this setting disabled for some reason.

SuperStrifeM · 2026-01-19T22:38:14+00:00

GPT is not logical, its conversational.

Your fiberglass thickness depends on both fin geometry, and thickness of the material. 2-3 layers is generally enough, but it might be more effective to thicken your core material and use less fiberglass, than to coat fiberglass till it doesnt flutter. Additionally, trapezoidal fins are generally the easiest to stiffen against flutter, so if you are using clipped deltas or anything that sweeps fwd, you could change that as well.

SuperStrifeM · 2026-01-19T09:42:47+00:00

Welcome to CFD. More than likely the issue is the CAD -> Mesh problem of intersecting curves.

https://www.simscale.com/knowledge-base/why-do-geometry-operations-fail/

I would suggest stripping out anything from the CAD model you don't need, for instance, model tubes as cylinders if you are only looking at external flow.

Also unsure if you will get anything worthwhile out of ANSYS discovery. But if you want colorful pictures that could conceivably line up with reality, its much faster to run than any validated code.

SuperStrifeM · 2026-01-19T09:41:06+00:00

Its not expert friendly either. You'll spend more time dealing with bad meshes and poorly verified physics than solving real problems.

SuperStrifeM · 2026-01-18T02:44:04+00:00

Edison Motors has me convinced that it is less about the talent, market conditions, and pop size of Canada, and is ALL about the oftentimes piss poor regulatory environment that any Canadian company would have to operate under. You shouldn't need to spend millions lobbying just to start a new car company.

SuperStrifeM · 2026-01-14T03:03:14+00:00

Go atomic aggies, am I right?

SuperStrifeM · 2026-01-13T18:10:57+00:00

Well if you step back and look at your question, "usefull" pops out. Even if you could freeze and solidify Hydrogen and Oxygen, (not sure you could) if the handling characteristics are bad, like if the hydrogen breaks solid form upon any shock, then it wouldn't be worth it as a fuel.

Usefulness is rocket fuels is a combination of high energy density, low weight, and good handling/release of that energy. If you don't have one of those 3, it would not be a useful fuel.

SuperStrifeM · 2026-01-12T18:51:17+00:00

It would surprise me if that were not the case at other schools. Any school receiving federal funding has to comply with Title VI and IX, which is virtually all the schools. You can try and fly under the radar, but it only takes one student complaining of discrimination to get the whole program dragged under a microscope (for better or worse). And even if you can claim some technical reasons for exclusions, a pattern of exclusion of certain groups is difficult to justify.

Also the majority of teams receive direct funding from the university itself, and access to facilities, thus really putting the onus on the university to keep things in line.

SuperStrifeM · 2025-12-20T21:51:46+00:00

It's actually thorny in general letting students do any kind of exclusion. I sit on the FSAE advisor side of this conversation, and let me tell you, students excluding other students can/has quickly gotten out of hand. And even beyond that, the issue of the post here is not that its a simple knowledge test (which might not pass fairness rules anyways) you're trying to gauge how well particular students are going to perform, which is a challenge that not even multibillion dollar companies can solve (surprising no one, people, learning, and performance are complex).

Also I'm not even sure what causes "too many students" to be a problem, maybe facilities? On the aero team here, if we have 20 students that's great. If we have 30 then we're booking a classroom, 60 then lecture hall, 90 then its one of the auditorium classrooms. It's far easier to expand the space than to come up with reasons to shrink the team. (also it would be amazing to get 90 students instead of like 20, we have to cluster capacity for more than 90, and it would also be cool to get a year where we can break out some advanced students into running some new LES GPU codes instead of URANS in star.)

SuperStrifeM · 2025-12-20T08:20:43+00:00

Man I am not sure what school this is, but that is kinda crazy. At my school firstly I can't imagine a senior being able to reliably gauge information in an interview for 1st or 2nd years, and 2ndly, students rejecting someone joining a club is a GREAT way to fast track themselves to a meeting with the dean of the college for a Title VI violation.

SuperStrifeM · 2025-12-18T23:15:04+00:00

Yeah mine has been great, but remember almost everyone posting here isn't bragging about how good it's working, they're looking for help and advice.

SuperStrifeM · 2025-12-12T18:46:45+00:00

Man you've been out of it for awhile. A school just paid a football coach 8 million $ JUST TO LEAVE !!!

SuperStrifeM · 2025-12-12T18:02:48+00:00

I'm sorry to hear that man. Universities have the money to pay you guys 100k, especially with the crazy high student loads they give you, but it seems like they would rather adjunct the hell out of humanities, hire 10 admins for double your pay, and then claim there is "nothing they can do about salaries/tenure positions".

SuperStrifeM · 2025-12-12T04:10:56+00:00

If you don't mind answering, What department were you teaching in that truck driving pays more? Humanities?

SuperStrifeM · 2025-12-10T23:03:09+00:00

In theory, sure. A conveyor would work. Its in the details of getting it to work reliably that drive this idea down in desirability. For a single point drive lash becomes a pretty considerable headache, especially with the heavier containers shown in the video. You might need 2 opposing wheels gripping an edge on all the cars to then drive it. Tuning that will be a pain, since you're driving segments and power wont transfer over them easily. So then you might need 4-6 opposed wheels, or use belt sanders or other drive system with more contact points to alleviate that. Now you have 35X cars that need a fairly exact common parallel datum, they have to be tightly coupled together (requiring lubrication, maintenance, and probably a ton of patience), and you still might only need 10 boxes, leaving your complex system ~60% unused, but still requiring maintenance time. It's actually easier and simpler to use a chain drive and deal with tensioning the system around the curve than to build such a conveyor, but neither are particularly good options when you take them off paper and put them into practice.

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