bernulli

9 ms·

31.
by bernulli 4y ago
Ok, you can adjust my illustrative example of O(100s-1000s) by the 30ms to account for a finite speed of light if you think that makes any difference to the argument. Let me know.
32.
by bernulli 4y ago
For another thought experiment: if you cannot hear that original first sound on take-off, which one can you hear? 10 miles from you? 1 mile from you? That will be the virtual first sound to you, determined by how much weaker the sound h
33.
by bernulli 4y ago
Precisely, "sound attenuation in the atmosphere and your hearing threshold".
34.
by bernulli 4y ago
So why don't you hear the sound when it all begins, right at take-off? That should be the first sound to reach you, no?
35.
by bernulli 4y ago
That's funny for someone with aero-glide2 as user name. I'm used to metric variometers in gliders.
36.
by bernulli 4y ago
Use the construction the author is using, i.e. the emanating sound waves, but you'll have to start them where it all starts, i.e. at take-off, and not simply appearing right next to you. Then, correct the drawing by having the plane mo
37.
by bernulli 4y ago
Nice, but very wrong. This describes the case of a plane suddenly appearing in mid-air and starting to make noise, something, planes rarely do (maybe in the Bermuda triangle). It's like thunder after lightning, or seeing a ball fly bef
38.
by bernulli 4y ago
Haha, thanks! Let me think about this! ;-)
39.
by bernulli 4y ago
You can create audible shockwaves, like the crack of a whip or a sonic boom, easily with your hands. It's called 'clapping'.
40.
by bernulli 4y ago
The conditions to reach sonic flow are surprisingly modest! It's fully characterized through the pressure ratio between high-pressure reservoir (here: inside of bottle) and low-pressure surroundings, and a parameter characterizing the
41.
by bernulli 4y ago
Well, yeah.
42.
by bernulli 4y ago
I always like to see it the other way around, it eliminates entities that are not a good fit, and the remainder is what drives adaptation. Of course, people could argue that's just like Michelangelo [1], and we're back at 'de
43.
by bernulli 4y ago
Haha, I wonder how this maps to the responses to the linked article in this very discussion forum ;-)
44.
by bernulli 4y ago
> elsevier is working with materials they dont own. however when substantial changes are made and accepted it could be argued that is a publishing partnership. I don't know what you are trying to say and how that addresses the quest
45.
by bernulli 4y ago
I can tell you exactly where it came from, it's being spun up in that launcher thing, obviously, that's the whole point of spin launch. You can see it for yourself in the video. Is the pointy end of the rocket always facing in the
46.
Ask HN: What Is Going on with Elsevier?
1 points by bernulli 4y ago|3 comments
47.
by bernulli 4y ago
How could it not? The angular momentum is just disappearing? Edit: Here's a link to an illustration, as your link provides zero information in that regard. https://www.youtube.com/watch?v=TGO4LtCctTk&t=141s&ab_c
48.
by bernulli 4y ago
That's barely enough for attitude control, do you have numbers how that could be used to despin a large rotating mass, as it is exiting the launcher ?
49.
by bernulli 4y ago
The only thing that’s valid (and I didn’t really understand if the video maker understood it bc he wastes so much time on the wobble) is that if you spin sth up to, say, 200 /s, then your rocket will spin, with its full length, at 200
50.
by bernulli 5y ago
Also - could you explain why you don't count van der Waals' equation among the cubic EOS?
51.
by bernulli 5y ago
That's what I work on, I'll send you an email (if I find your address somewhere)!
52.
by bernulli 5y ago
Regardless of why you get to supercritical conditions, once you have them, that's plenty of reason to care about what supercriticality does in industry. You want high pressures to achieve a high efficiency of a process (gas turbine, ro
53.
by bernulli 5y ago
I mean something different: no one has ever measured a critical volume, your dp/dv flatlines at the critical point, i.e. there is no driving force to make the fluid balance out the naturally occurring fluctuations, indeed relaxation ti
54.
by bernulli 5y ago
Super interesting, and I watched the video on GitHub! Of course, for an EOS to be useful at the critical point you have to believe that there is such a thing as continuum or even thermodynamic equilibrium at the critical point ;-)
55.
by bernulli 5y ago
There’s plenty of applications beyond using them as solvents, e.g. fuel injection in jet engines, Diesel, or rockets; cooling in power plants or rockets; drilling; power cycles, etc.
56.
by bernulli 5y ago
There is nothing magical about a supercritical fluid (SCF), i.e. a fluid at a state that has a temperature and pressure higher than the respective critical values. The article repeats the same crap that you read other places: it does not
57.
by bernulli 5y ago
Same thing, you will want to reuse existing code, and you do not want to split knowledge in your student group. There is no such thing as 'gradual' migration: I either have to support Python in my group, or Python and Julia -- u
58.
by bernulli 5y ago
Its third, and major, drawback is that Python has a legacy in many groups.
59.
by bernulli 5y ago
For those unfamiliar, CERFACS (Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique, i.e. European center for research and advanced training in scientific computing) is a leading research institution, with two main br
60.
by bernulli 5y ago
That’s also Newton’s 3rd.

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