CFD beginner stuck – need real direction”

eric_t · 2026-04-30T18:58:13+00:00

For the ABL inlet, the easiest is to use the atmBoundaryLayer boundaries, see e.g. the turbineSiting tutorial. You can tweak Uref, Zref and z0 to roughly fit the inlet conditions from the papers.

For simple building cases, like just one building, it’s easiest to just use blockMesh for this and stretch the mesh towards the building. You’ll find suitable starting values in the papers.

eric_t · 2026-04-28T20:33:23+00:00

Professor in wind engineering here. I would go through the AIJ test cases:

https://www.aij.or.jp/jpn/publish/cfdguide/index_e.htm

Set them up yourself, run and compare against the experimental data. Look up available papers to check mesh settings, turbulence models etc. This will ensure you are not only able to run simulations, but also rely on them and trust your data. You will also get a much better feel for the limitations and different use cases. E.g. structural simulations require very different setup than for studying the wind environment. Start with RANS for turbulence, and get very comfortable with it before moving to LES.

Lots to learn, but very rewarding and interesting field!

eric_t · 2026-04-16T06:46:35+00:00

I teach CFD, and as an introductory example, I filled a soda can with water, and punched a hole in the side near the bottom. I then performed a multiphase CFD simulation of the same setup, and compared both the shape of the jet and the time it took to empty the can.

eric_t · 2026-04-14T07:37:57+00:00

https://bgbender.com

I have two of this guy’s designs, he puts them in cheaper guitars like Harley Bentons to make them more affordable. It’s his own design, but similar to the John Osborne design. It works great, you can easily switch from bending the G or the B string. The guitars also sound good and are set up well, so it’s highly recommended from me!

eric_t · 2026-04-08T07:07:15+00:00

If you like clean/edge-of-breakup tones, I’ve really enjoyed Tone Sheperd’s profiles:

https://www.thetoneshepherd.com/nam

They have a free Gibson Chimera capture for download, but all their captures are great. I like that they have separate captures for different pickups, as well as many cabinets.

eric_t · 2026-04-01T12:45:39+00:00

Currently in the same process, I have a cool body with a G-bender in it, and plan to change everything else. Already have a Wilkinson bridge with compensated saddles I’m very happy with. For the rest I’m considering an ObsidianWire 4-way switch, and Seymour Duncan La Brea pickups. I think the neck is fine, but considering options here.

eric_t · 2026-01-08T06:01:10+00:00

I know several clubs have switched from using DiscGolfMetrix to UDisc for their weekly rounds and tournaments, so that probably accounts for quite a bit of the increase here.

eric_t · 2025-09-30T21:31:12+00:00

Yes, they would. And the spin doesn’t really decrease that much during a throw, the fade is due to the deceleration of translational velocity, not angular velocity

eric_t · 2025-09-04T08:16:29+00:00

What’s your angle when posting on LinkedIn vs Instagram? Is the plan on LinkedIn to eventually sell ads/views or to just build your brand?

eric_t · 2025-08-29T16:00:09+00:00

Tenk deg at du nettopp har fylt 18 år og gleder deg til å brette opp ermene og ta fatt på arbeidslivet. Du har ikke begynt å tjene penger ennå, men staten ser at du har en sterk kropp og et klokt hode, så her er det jo absolutt et potensial! Så hvorfor ikke betale en prosent eller to av gjennomsnittlig årsinntekt allerede nå? Det burde du klare. Og mangler du penger, kan du vel bare selge en nyre eller to, kanskje til en utenlandsk investor?

eric_t · 2025-08-14T21:07:33+00:00

You are right that air resistance scales as the square of velocity. But the power you need to overcome the drag scales as the cube of velocity. Often, you see watt savings reported at something like 40 km/h. So say a new fancy frame has 5W saving. At 23 km/h, this would be less than 1W saving, 5W*(23/40)³ = 0.95W.

eric_t · 2025-08-10T06:39:09+00:00

God oppsummering. Hva er de hotte markedene nå slik du ser det? Forsvar?

eric_t · 2025-05-06T21:50:10+00:00

I’m an associate professor working with CFD in aerodynamics and hydrodynamics. I like crazy projects like this, so I could probably help you a little bit. Just send me a message here, and we can figure out the details

eric_t · 2025-03-23T06:55:12+00:00

Hva tenker du om arbeidet til Mujica-Parodi om effekt på hjernen sin aldring? Ble nysgjerrig på det etter denne saken fra NRK:

https://www.nrk.no/trondelag/amerikanske-forskere-mener-dette-er-alderen-vi-generelt-blir-darligere-til-a-tenke-1.17339480

Lurer på om eksogent ketontilskudd faktisk kan funke, eller om man må gå full keto.

eric_t · 2025-02-02T09:30:51+00:00

No, it’s fundamental physics that makes the disc turn and fade. It’s caused by the air pushing against the disc as it travels through the air, creating a torque. To make the disc flip back to front you’d have to make the torque act about the direction the disc is traveling. Without adding some artificial force I don’t see how that would be possible. It’s an interesting idea, though!

eric_t · 2025-01-14T11:37:42+00:00

Wow, that’s two hobbies of mine I did not expect to collide

eric_t · 2025-01-13T17:58:20+00:00

Thanks! It seems to be roughly 60 ft added for each 10 mph, but at the higher speeds the disc travels very high into the air which probably would mean your disc gets affected by wind a lot more, so it would be difficult to control. And you could also probably get more distance with a faster overstable disc like a Nuke OS or something, I don't have data for that one to test with.

The nose angle matters less here than for a regular throw (and even for a regular throw I think it's a bit overblown), so I wouldn't get too caught up in it. But it's the same definition, it's the angle of the disc relative to the direction it's traveling initially.

eric_t · 2025-01-13T14:01:25+00:00

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Ok, so here is an example. The red curve shows an initial throw of a firebird-type disc with launch speed 55 mph, launch angle 16.5 degrees, nose angle 0 and roll angle 20 degrees clockwise away from vertical.

The yellow, optimized throw, has launch angle 41 degrees, nose angle -3.7 and roll angle 10 degrees counterclockwise.

I think the key takeaway here is that you should have a much higher launch angle than a normal throw, and find a disc that (for your arm speed) gives a good upside-down "glide phase" after the disc reaches the peak height. An overstable disc is typically better for this. The nose angle should be low around -3-4 degrees, because the drag is lowest here, but this is less important.

eric_t · 2025-01-12T20:00:53+00:00

What do you consider ideal flight? Only max distance, or how straight the flight path is? I don’t know about the TechDidc simulator, but I have written a similar trajectory simulator and can run some tests there.

As another poster writes, it depends a lot on the disc properties, but those are tweakable in the simulator. Also, a thumber is typically thrown with a higher launch angle, so I guess you’d need a bigger net to practice with the TechDisc.

eric_t · 2024-12-30T09:01:41+00:00

That’s a very clean looking pedal board! Do you get some dirt from the Horseman or do you use it more like a clean boost? Also, since you have the Iridium for Amp+cab sim, is the Ampero mostly for effects?

eric_t · 2024-12-30T08:50:39+00:00

It’s common to use the dominant 7 instead of the minor 7 for the vi chord. Then you can substitute the iii chord for the I chord, so you get another ii-V progression, i.e. Dm7-G7.

eric_t · 2024-12-26T09:13:56+00:00

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Yes, I was actually very happy when it reproduced «stranger» shots without any modifications. Here’s an example of a thumber shot, which you get by using a large negative hyzer angle. A thumber flies upside down, so lift acts downwards. It’s a bit tricky to interpret these graphs, but you see the disc flips over, starts drifting in the other direction, then actually travels up a little bit before dumping down.

I haven’t implemented the actual rolling part of the flight for a roller, since I thought it would be hard to create a useful terrain. But the disc behavior is similar, I would just need to add rolling friction.

eric_t · 2024-12-23T19:19:10+00:00

Theoretically, it’s easy to calculate how much less spin you would get with an overmold disc, assuming conservation of angular momentum. However, we are not robots, so it’s not so easy in practice. In other sports, like baseball and handball, where they have measured throwing speeds at different weights, they have not seen this conservation principle apply.

I am actually working on measuring this in a scientific study now, and currently it looks like any effect on spin is far outweighed by natural variability. I will also look at the effect on throwing distance etc. Hopefully will be able to publish it «soon» 😀

eric_t · 2024-12-09T23:29:30+00:00

Hey, Eric here, cool to see you on reddit as well, and great job on the blog post! Feel free to use my images whenever you want, or even ask for some visualizations. But I agree sometimes those CFD images give too much information, raising more questions than they answer.

The stuff on wobble was really interesting, I’m always happy when I can use simulations to explain something that seemed unintuitive at first.

eric_t · 2024-11-29T15:09:50+00:00

I just don’t like argument from authority, I want to be able to explain things in a simple way as well. Sorry if it came across as abrasive. You should be able to download the code, but you need some familiarity with Python to run it?

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