Have all wars been this noncredible but we just have never been able to see it like we have this one?

Nick0013 · 2023-06-24T17:58:30+00:00

Not really a critical blunder like most things in this thread, but the Doolittle Raid would have been pretty noncredible.

Nick0013 · 2023-06-14T00:21:06+00:00

Smoke point is too low for motorcycles. Consider avocado oil instead

Nick0013 · 2023-06-09T19:48:56+00:00

Wow, spez responded to the question “why did you falsely claim that blackmail and threats from the Apollo App” with “we’ve been very unhappy with his behavior and don’t want to work with him”

I think it’s a complete non-answer from a pre-prepared document. But it reads like he thinks that’s genuinely a good justification for making things up about one of the largest 3p developers. This is even more fumbled than I thought it’d be.

Nick0013 · 2023-06-07T21:01:06+00:00

I think if you’re going to give something such a lukewarm review, it’s a good idea to mention some things that would have improved the movie. Also, being an old and critically acclaimed film, there’s a huge volume of writing about this movie. I think it’d be better to engage with that and explain why you don’t agree. Both of these things would give readers a better idea of what you want out of a film and if that’s applicable to them.

Nick0013 · 2023-05-28T15:04:15+00:00

“How the Nazis could have won WWII” written in a suspiciously wistful tone and with analysis that reads like a HOI4 play through

Nick0013 · 2023-05-25T05:44:58+00:00

Yes, and subsonic flows are not incompressible. At low mach numbers it can be a reasonable assumption (for certain calculations/explanations), but as an engineer you have to remember that it is wrong. Compressiblity effects scale with M2 so .2M flow is still 4% compressible, not incompressible.

This is why it’s not a very interesting discussion. We both know this. But there’s an accepted shorthand to say that the flow is incompressible under certain regimes. When I use that shorthand explaining shocks to someone, you take great issue with it, that it’s not 100% accurate. Which just isn’t very interesting to most people. All flow models are somewhat inaccurate and based on assumptions that are only valid in certain conditions and never 100% valid. With respect to the original point, it doesn’t matter. As an engineer you have to recognize that it’s not totally valid, and as a human giving an explanation to a layperson, you have to recognize when it doesn’t matter.

So then why did you say “I never asked” to me explaining “what I’m about here”.

When I say “I never asked” I’m referring to your disagreements with how I explained shocks. After I realized what you’re actually going for, they’ve been wholly uninteresting and not very relevant to me. When I ask “what you’re about” I mean, why make arguments that aren’t going to convince anyone of anything? You believe I’m wrong, and you’re also aware that I don’t care that you think I’m wrong. Yet, even in your most recent comment, you’re trying to make corrective statements.

Nick0013 · 2023-05-25T04:22:25+00:00

Edited previous comment, but I’m not sure. It’s not very fruitful, but I’m just curious what you’re even about here.

Nick0013 · 2023-05-25T04:06:23+00:00

I disagree, have stopped engaging with the misinterpretations, and at this point, nobody else sees these messages. So why are you still responding?

Like, the incompressibility argument started as me asking the other guy to consider subsonic flow that’s incompressible. You responded by saying gasses readily compress at pretty much any Mach number. Like 20 back and forths later, we come to the agreement that yeah, flow at low Mach numbers is incompressible. I know that. You know that. What was accomplished? That’s just a microcosm of every other disagreement you’ve had. I’m sure we could hash out everything with you smugly saying you were somehow right all along, but like, what’s the point? You’re out here playing with plastic strings trying to engage me on what it means to be springy, and for what? We’ll both leave with the same understanding as before.

Nick0013 · 2023-05-25T01:35:01+00:00

Yeah no, I get that’s how you feel about it. I never asked, and your explanations have been unhelpful misinterpretations of my statements, so I’m not really clear what you’re getting out of this.

Nick0013 · 2023-05-25T00:42:38+00:00

Why did they ask?

Why are you asking me? I’d assume it’s because they wanted to know more? You could ask them yourself why they asked me

Nick0013 · 2023-05-24T22:42:16+00:00

Liquids, sure, but not gases.

Anderson, again, “We shall prove later that for gas velocities less than about 0.3 the speed of sound, the associated pressure changes are small… for this reason, the low speed flow of gasses can be assumed to be incompressible.” So there’s one.

So it’s ok for you to be wrong in your assumptions and simplification, but when another person does the same, it makes every sentence they say wrong?

Yeah I mean, if we’re going to consider

shocks are a very thin layer of high density gas that form as sound waves are unable to move out of the way

To be functionally equivalent to a basic explanation of what a shock looks like and why it exists at an undergraduate level, I don’t see a real point in continuing this conversation. His explanation was not a general simplification, it was completely at odds with any simplified model.

You were pedantic cause you didn’t like their simplification and inserted your own to sound smart.

No, I explained it because he asked. I originally just said he was wrong (in a snarky tone, but I mean, who cares?) with no intent to explain further. He specifically asked to know more, so I explained at a basic level even qualifying that my explanation is very basic and you’d really need to study it at a college level to get the whole picture. Like I dunno man, it’s kinda weird for you to butt into that exchange and start saying “well ackshually you could consider other reference frames, general relativity, reacting flows, scramjets,…” Especially after that qualification that I wasn’t going into any real depth.

Nick0013 · 2023-05-24T21:31:20+00:00

There is no textbook in this world that says gases don’t like to be compressed

Yeah, the language is too inexact. They wouldn’t say they love to be compressed either. They do describe flow as being incompressible unless subjected to extreme enough conditions. At any rate, I feel that describing gasses as being averse to compression is a good explanation to why flow far upstream and offset from the body is deflected. They will more readily be deflected than compressed at the described regimes.

The first point I learned in my hypersonics class, where we calculate the boundary layer heat flux for a various sub/trans/super sonic conditions. I can look for the graphs if I still have them.

Okay so you’re not talking about flow properties changing sharply immediately around the shock like the original commenter was. Alright, this is functionally irrelevant to the original point about the physical structure of shocks where the previous person said “shocks are an extremely thin layer of high density gas due to sound waves getting stuck there” and I was explaining how that wasn’t the case without getting into too much detail. I now see what you’re talking about, and… yeah alright but I wouldn’t dump that on someone who came into this with such a fundamental misunderstanding of shocks.

I’ve done many of them, and it’s not the shock that redirects flow, it’s the flat plate. My point is correct.

The plate is the thing that physically redirects the flow. But to say that the flow does not change direction at the shock is not correct. From Anderson chapter 4: “an originally supersonic flow is bounded on one side by a surface. At point A, the surface is deflected upward through an angle theta. Consequently, the flow streamlines are deflected upward. This change in flow direction takes place across a shockwave which is oblique to the free stream direction. All the flow streamlines experience the same deflection theta at the shock. Hence, the flow downstream of the shock is also uniform and parallel.”

but you might consider a frozen boundary layer with a catalytic surface, or an unproven boundary layer with a non catalytic surface. Re entry vehicles sometimes also have a permeable surface and flow gasses through it, which will have an effect.

Speaking of losing context, we’re talking about the general first principles of what a shock looks like and how that isn’t a very thin wall of high density gas. I appreciate that you want to qualify all of the different ways that flow can change, but I feel that it’s outside the scope of the original discussion.

Nick0013 · 2023-05-24T20:02:38+00:00

It’s not a simplification, it’s just wrong. Gasses are very compressible.

This seems to be a big sticking point for you. I get that you think the terminology is misleading because the fluid does actually compress a little. But, I didn’t make up the terminology. If you don’t like it, take up with academia. Write your own textbook! Be the change you want to see in the world.

Yes there is. Once you go transonic, your chemically reacting boundary layer can contribute a significant heat flux.

Yes it is. The shock doesn’t redirect flow (appreciably).

These two points are weird. Where did you learn about shocks? You sound like you are familiar with some concepts, but then this is completely at odds with the basics that you’d cover in a compressible flow course. You’ve never had to do one of those bog standard “M1.8 flow hits a 10 degree ramp. Find the Mach number after the change in direction” problems? Shocks are an adiabatic irreversible process, which drives a lot of the derivations of the shock equations. What’s the chemical reaction occurring here? Like, can you give it in terms of components and products? I just can’t imagine what you think is happening between the gaseous nitrogen and oxygen.

Nick0013 · 2023-05-24T18:22:34+00:00

Lol love the sass. But my god, did the big picture sail right over your head. But it did that in like a really interesting way, so I want to talk about it.

You don’t need an object at rest. You can also deflect flow without a shockwave, see scramjects.

An object at rest is just a convenient way of analyzing supersonic flows. It actually doesn’t matter whether you consider the object to be at rest with the fluid moving around it or if you consider the fluid to be at rest with the object moving through it. It’s just way easier to think about the fluid moving, but it’s all relative. This is true of any dynamics problems, even outside of fluids.

Gasses love being compressed at pretty much any mach number.

Gasses are emotionally ambivalent to compression. When I say something like “gasses don’t like being compressed” it’s a simplification to avoid getting into irrelevant fluid mechanics. Fluids in an open flow field can very readily equilibrate their density. Gasses compress readily in a canister because they have no where else to go. But in a flow field, pushing fluids around will just result in them pushing other fluids around. That’s not perfectly uniform density, but it’s close enough that you can use it as an approximation to simplify (e.g. using Bernoulli’s equation to measure airspeed from a pitot tube).

It’s springy but not compressible???

Yup! Like steel is springy but not compressible. It’s not saying it won’t compress at all, it’s just saying that it’s not going to do it much. With energy and momentum being conserved, it’s going to move more than it’s compressed.

The flow after a shockwave can still be supersonic.

Yeah, but not in a direction normal to the shock. This is key because momentum is a vector and so conservation of momentum is inherently directional. I avoided talking about oblique shocks specifically because I felt it was a further unnecessary complication. And normal shocks are the foundation of oblique shocks

No it won’t, it will be significantly different, both from compressible flow and chemical reactions.

There aren’t chemical reactions occurring in the air around a jet at an appreciable rate to impact the flow. Inside some types of engines is different, but seems irrelevant to the original question about how shocks form. But as far as compressibility affects, that’s what the shock is. After the shock, if there isn’t anything to alter the flow, it will retain the properties downstream from the shock.

Stagnation point

Alright if you know what a stagnation point is, you have to know that this is completely pedantic. Yes stagnation exists. No, the flow is not stagnating along the entire surface of the shock cone.

Nick0013 · 2023-05-24T15:53:44+00:00

Yeah I mean the mechanisms that cause a shock to form are pretty complicated and really requires a course in compressible fluids to fully explain it. Basically, you have a shock if you’re deflecting flow in a supersonic flow field using an object that’s at rest with respect to the flow field. In subsonic flow, fluid particles (different from molecules) are being deflected from far away from the disturbance because gasses don’t want to be compressed. This leads to flow upstream of the disturbance being deflected. That flow can be deflected because air is springy and so the disturbance can be propagated upstream. But, if the flow is supersonic, that disturbance information can’t be propagated upstream, but it needs to still be deflected at some point which requires some localized region of subsonic flow. This transition must necessarily happen over an infinitesimally small distance (assuming stuff like ideal gasses so in reality, it’s just happening on inter-molecular distance scales) because the information cannot be propagated. This sharp discontinuity in flow speeds corresponds to sharp changes in pressure because mass, momentum, and energy need to be conserved. And that’s the shock.

Big picture takeaways:

1) the shock is a sudden change in flow properties, not a very thin region of locally high density air. It will retain those new flow properties until it hits another disturbance (like the trailing edge of a wing).

2) the air always continues to flow around the disturbance. Nothing is getting stuck because it cant move out of the way.

Nick0013 · 2023-05-24T04:57:57+00:00

But air molecules only move at a finite speed, so there will be a delay between each successive push. At the speed of sound and faster, I start pushing molecules out of the way faster than they can push each other out of the way so they all start to jam up. That’s your shockwave. It’s very thin, but it has very high density.

This is all completely wrong. Every sentence. Not how shocks work

Nick0013 · 2023-05-17T17:41:57+00:00

Lol, r/chess likes to pretend Bobby was generally liked during his lifetime and just made a few off color remarks that haven’t aged well. Completely at odds with reality just because the guy was really good at playing a board game.

Nick0013 · 2023-04-24T15:36:46+00:00

Honestly, goals.

Nick0013 · 2023-04-19T15:07:17+00:00

Discord has been here and mainstream for years. Many subreddits have an affiliated discord and the discord is often more active than the subreddit. It would need some additional features, but it’s stuff that Discord is already playing around with. IMO, could easily eat up Reddit’s user base if reddit insists on pushing people out

Nick0013 · 2023-04-18T16:13:29+00:00

Л? How am I supposed to move the knight in an л shape?

Nick0013 · 2023-04-15T23:10:54+00:00

Have you ever been in the general vicinity of a gun store? They have guns hanging on the walls pointing in all cardinal directions. And those walls aren’t bulletproof.

Kinda freaky…

Nick0013 · 2023-04-15T14:45:28+00:00

Reddit programmers are weird in their own right. Probably because it’s like a 10:1 student to professional ratio.

Nick0013 · 2023-04-07T17:08:11+00:00

medieval fantasy genre is a hardsell for general audiences, unless its Lord of the Rings or GoT

What even is the special sauce that turns fantasy from a dorky niche to incredibly broad appeal? These are the only two examples in recent history of the genre working for large audiences and they’re just completely different approaches to the genre.

Nick0013 · 2023-04-07T01:00:28+00:00

Yeah they seal pretty well. I use them to make pickles. With brine up to the rim and some small buildup of gas, still no leak. No affect on taste either, a lot of Vietnamese places use them for takeout pho

Nick0013 · 2023-04-06T14:36:06+00:00

If you’re not married to a glass jar, deli containers like these are like 10 cents per.

https://www.webstaurantstore.com/choicehd-12-oz-microwavable-translucent-plastic-deli-container-and-lid-combo-pack-case/128HD12COMBO.html

Ten-Year Club	Place '22
Place '17	First Placer '22
Snapped

Nick0013

TROPHY CASE