What I really, really respect about Dr Diaz is that, aside from his brilliance shown just from his videos, he took the exercise to derive the energies from the Beirut explosion - and got it RIGHT (even as verified with corroborating, yet independent studies from experts on explosions) - and then took the nitpicking responses after publishing as a means of learning more - and then went even further with his continued education of sorts here to hone his skills in that area of expertise. That’s just smart all the way around. His generalized solution for all explosive types - derived from STvN and his ansatz - allowing anyone to well-estimate explosive yield by video footage by position and time - that’s awesome. So useful! Kudos!
@jkzero
8 ай бұрын
Thanks for your kind message and thanks fro appreciating the efforts and sharing of learning experiences. I made mistakes because I adventured into a field beyond my expertise but got those mistakes pointed out in a professional manner by reviewers. That is how a healthy academic environment should always work. In my case I benefited from this. I learned something new and my research got better, the paper got better, and those who read the paper can benefit themselves from that. In fact, I included a footnote in the final paper explaining how I got it wrong first but it was latter corrected, I don't see the need to hide those experiences.
@Dr_LK
11 ай бұрын
Excellent presentation. Thank you. The way of explaining and presenting results is clear, efficient, and to the point.
@jkzero
11 ай бұрын
Glad you enjoyed it! Great that you found the content of interest, make sure to check the several follow-up videos. Thanks for watching and welcome to the channel.
@fave7824
7 ай бұрын
As a material science/engineering student I must say that this video and how it was explained were great. I think this would be a great way to show to motivate why to learn for example differential equations and many other practices
@jkzero
7 ай бұрын
Thanks, I am glad you found the content of interest. I am glad that this seminar that I gave years ago continues to be watched.
@jbflores01
Жыл бұрын
absolutely fantastic video! very well explained!
@jkzero
Жыл бұрын
I am glad you found the video of interest, you are welcome to check the other videos, share and subscribe, thanks
@shandusa
Ай бұрын
Gracias por la excelente explicación.
@BerndUlmann
Жыл бұрын
Amazing work!
@jkzero
Жыл бұрын
Glad you think so! Thanks for watching.
@alans172
7 ай бұрын
At the time of my post on your great Planck video, I had not connected you with the Rigby and Diaz "Kinematics of Blast Wave" paper. Now that I have, I would welcome your thoughts, as a postgrad physicist, on a paradox that I observe in fluid dynamics. In his response to some questions I posed to Sam on his "Negative phase of the Blast Load" paper, his response centred on the concept of particle velocity which, to me as a mathematical physicist (with a poor pass degree), I have always found perplexing. When pressed on the physics of this "particle" he ultimately responded : "These are well established terms but aren't my area of speciality". It seems to me that the equations of fluid dynamics hold true for fluid particles with pressure, density and temperature, but fail as the particle size tends to zero, since Kinetic Theory provides an actual physical size to molecules and their mean free path in air and, as we physicists know, molecules do not possess the properties of pressure, density and temperature. It seems to me that fluid dynamics has encountered a problem similar to Planck's discretization of energy for his oscillators, having e= kv and not taking e->zero. Planck's paradox was resolved by Quantum Mechanics. Do you think the Navier Stokes equations will be solved by Quantum Thermodynamics, or is there really a hole in fluid dynamics?
@jkzero
7 ай бұрын
I received your email, I will make sure to get back to you on this
@alans172
7 ай бұрын
@@jkzero I wonder if you have had a chance to get back to me? I have revisited the section of your video from 53:51 discussing the condensation cloud phenomenon and note that, unlike Dr. Rigby's explanation, you make no mention of particles of air in the explanation. I would like to understand whether, if Rigby's air particles explanation is correct then what is the nature of the air particles, and if not, what causes the negative phase of the blast wave? I accept your explanation that the overpressure of the blast wave is followed by a rarefaction, but I am interested to understand the cause of that rarefaction, not just back to ambient pressure, but to a value significantly below ambient pressure. I look forward to hearing from you.
@jkzero
7 ай бұрын
@@alans172 I apologize for the delay to reply but I am in the middle of a significant trip. The reason for the rarefaction is just the return to ambient conditions after the pass of the compression wave, it is like the reaction to an action. As for the cloud condensation, Sam is not incorrect, particulate material highly enhances the production of clouds by nucleation.
@alans172
6 ай бұрын
@@jkzero In your video, you eloquently DESCRIBE the concept of "rarefaction," as a reduction in pressure below ambient levels (the negative phase), which occurs after the compression phase and before the pressure returns to ambient. I understand that, as the pressure and expansion rate of the fireball decays over the microseconds of the detonation, and its shock front velocity reduces to the speed of sound, a blast wave detaches as a pulse of high pressure that then propagates outwards into the undisturbed air. My question is, instead of returning to ambient pressure, the pressure drops to BELOW AMBIENT. Can you explain what CAUSES this under-pressure or negative phase? I hope you are having an enjoyable trip and I look forward to hearing from you.
@jkzero
6 ай бұрын
@@alans172 the pressure returns to ambient conditions but it does not simply drop from P to P0 but overshoots and bounces back, imagine the air as having some elastic property, this is just an analogy, but it is not far from reality. The pressure goes very fast up with some momentum, then it goes down with a momentum in the opposite direction but does not stop when reaching P0, it keeps going beyond P0 (this is the so-called negative phase) and then back to P0. Notice that pressure is not negative, it is just below the ambient pressure P0. What is negative is the overpressure, defined as P-P0, this is the deviation from P0. For details you might want to check the popular "Effects of Nuclear Weapons" it is available online for free. It has a long and detailed chapter on the blast wave and stages of the overpressure.
@afrolichesmain777
7 ай бұрын
I recently stumbled into your channel and im loving the content! I have no background in physics at all, but I would argue you can justify your selection of the zeta function with a Taylor series argument. In particular, since lambda is the inverse square of the Mach number, we can assume lambda
@jkzero
7 ай бұрын
You are correct on the selection of zeta, that was in fact the idea and we call the linear expression just an approximation. Thanks for watching and for the feedback. I am curious to know what brings viewers to the channel, in particular to this academic seminar. Were you searching for something in particular or did the 'mighty algorithm' find you? Saludos desde Alemania.
@afrolichesmain777
7 ай бұрын
@@jkzero I see. In my case, the almighty KZitem algorithm led me to your video on calculating the critical mass of an atomic bomb. I recently finished my graduate degree in applied maths, but havent had a job in industry, so I like to watch videos with advanced mathematics to keep my maths fresh and learn new things. Looking forward to your future material!
@jkzero
7 ай бұрын
@@afrolichesmain777 wow, thanks for sharing and I am glad the algorithm is working, I hope you find the other videos of interest too and welcome to the channel. New video already in production, coming soon
@CookieCutterPeanutButter
10 ай бұрын
More hour videos NOW...
@kutay8421
3 ай бұрын
Excellent Mathematical and Physical Skills, I envy and congratulate you Dr Diaz. May I ask you to calculate and inform me if it is possible to move Anatolian Sub-Plate with the help of pneumatic pressure of an atomic bomb, underneath it? This is a relatively small plate (~600km in diameter, 12 km in depth) and the continental drag is about 21mm/year. Would the pneumatic pressure of any feasible nuclear bomb will suffice to overcome the friction between this sub-plate and Arabian plate beneath it? Thanks and bless you for your wonderful effort & uploads ❤
@wijpke
2 ай бұрын
I would love for you to simulate the blast radius for a specific mass of TNT
@jkzero
2 ай бұрын
thanks, but simulating these phenomena goes beyond my expertise, there are dedicated codes for this kind of simulation but I have no access to them.
@istvanvacz5263
3 ай бұрын
10/10. Thx a lot. :)
@jkzero
3 ай бұрын
Thanks, I am glad you liked it. Make sure to check the new videos in the channel.
@wijpke
2 ай бұрын
Very cool what would the blast radius be under water?
@jkzero
2 ай бұрын
Underwater blast is complicated, it is tempting to simply replace the air density by the density of water; however, this would incorrect because several assumptions used for solving the system of equations only apply to air. Underwater explosions require a dedicated analysis that I have not done because it is also hard to get reliable data underwater.
@omargaber3122
8 ай бұрын
Done❤
@christoffel840
7 ай бұрын
Can you give me a hint for how you get the blast energy relation at 25:36? Do you take the hydrodynamic derivative of both sides?
@jkzero
7 ай бұрын
it is simpler than that: from the definition of K(\lambda) shown on the fifth line (left), simply take the derivative wrt \lambda and rearrange terms using the definition \zeta(\lambda) and the conservation of energy relation again (fifth line) to eliminate z in terms of K, this gives the final blast energy relation. In case it is still unclear just let me know here and I can share a full worked-out explanation. And thanks for your interest.
@ДаниилИванов-г3ж
11 ай бұрын
24:41 How did you come up with the definition of zeta ? It was the only confusing part for me. Also I didn't really get the transformation of Hydrodynamic derivative where D/Dt ~ (Ф - eta))d/d eta + ...
@jkzero
11 ай бұрын
the second part of your question comes first: you must take the hydrodynamic derivative and transform the coordinates (r,t) to (\eta, \lambda), it is a tedious calculation but it must be done with care using the Jacobian of the transformation. When you do this, you get a term proportional to d\lambda/dR; this also appears when calculating the energy so it was useful to give it a name. To make it dimensionless it was defined proportional to R/\lambda and that is how z(\lambda) was introduced. It is just a useful auxiliary function to have around and avoid writing d\lambda/dR many times.
@Chris-ux1ij
Жыл бұрын
Can you explain a little bit more how you got the Fermi result? There is a paper arXiv:2103.05784v2 that states he observed pieces of paper (that act as Lagrangian tracers of its motion) that moved 2.5 metres and got the correct order of magnitude answer of 10kTNT. But there doesn't seem to be any good analysis of how he got or could have got such an answer. He would have made some cute little analysis and then probably went to his favourite hand crack calculator to make some numerical estimates that he put in a little book. On the day he just looked up what value he got in the book from knowing the bit of paper moved a certain distance while being much further away from the blast where the analysis is different to that of Taylor et al.
@jkzero
Жыл бұрын
I did not derive the Fermi result, in fact I didn't even use it; when I mention Fermi for the plot of the Trinity blast wave the only information I am referring to is the time of arrival of the blast wave at the observation point. I have looked several times for a clear derivation Fermi's result from his famous pieces of paper; however, I have not been able to read a satisfactory derivation to date. You are correct about the way Fermi prepared for Trinity, I think it was Feynman in a interview who said that Fermi had precalculated the displacement of his pieces of paper for different explosive yields so at the actual test he looked at the displacement and compared to his table to get the yield.
@patrickgisler4061
7 ай бұрын
Impacts create similar results to explosions. But I do not understand how to do the math when the impact velocities leave the range of 25 km/sec as for many solar system derived objects to hyper velocity objects, up to 150 km/sec for objects from within the galaxy neighborhood, to ultra hypervelocity objects such as generated from a supernova (1000 km/sec), to rogue star collision generated objects (12,000-35,000 km/sec) to alleged near black hole collisions generating objects moving at up to up to 85,000 km/sec where reletavistic factors come into play. All of these velocities are present in our surrounding galaxy and have some likelihood of having impacted this planet. What would an impact structure look like if a supernova generated an object traveling at 1,000 km/sec which impacted the Earth?
@jkzero
7 ай бұрын
I find it hard to give a justified estimate when it comes to impacts because speed is very important (because kinetic energy goes with the squared of the object speed) but there are also other factors like the mass, the density, and the type of material of the object. Some material get quite affected during the atmospheric entry and get highly reduced in speed and mass before impact.
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