sethoflagos

Whoever constructed this chart has assumed water to be incompressible. Many people do. However, the bulk modulus of water is not infinite, it is 2.2 GPa. The over pressure due to 4,000 metres of seawater is around 2% of the bulk modulus so consequently the density at this depth is around 2% higher. So I guess that's the basis of the 1,050 kg/m3 figure and clearly the cartoon presented is significantly inaccurate. But that's all by the by. Something has to persuade the flow to spread out horizontally at the top of the 7 km diameter pipe, and that's a flat topped mound of water oto 25 metres high. This provides the potential energy necessary to source a 10 metre deep, 20 m/s horizontal outflow at the pipe circumference. Hence the 2.5 bar/1000m and 1TW estimates still stand. . 6.3 m3/s vs 40,000,000 m3/s Didn't someone mention a bit of a scale disconnect earlier in the thread?

Here

Before anyone looks too closely at it, I should point out that while 2.5 bar/km is a reasonable order of magnitude estimate for pipeline pressure losses, the rationale I gave for the figure is a bit of a nonsense. Oops your kind rep just disappeared, so I guess someone has just woken up.

Just some back of envelope stuff. Recast the objective as the transport of a nominal 100 tpd of deep ocean dissolved iron to the surface. Typical deep ocean iron concentration (from here) seems to be around 0.5 nM which sets the pumping volume to a little over 40,000,000 m3/s. While it is correct that the external water column does largely support the pumping effort, deep ocean seawater density is generally taken to be around 1050 kg/m3 as ooposed to the 1024 kg/m3 of surface waters and that 26 kg/m3 difference does give a static pressure difference of around 250,000 N/m2 per 1,000 m. If upward velocity were negligibly small (really huge diameter pipe) then a 100% efficient pump would consume a minumum VdP of 1TW / 1,000 m. As we're already exceeding the electrical power consumption of China and haven't yet touched on friction losses, I see little purpose in pursuing this further. Tankering in liquid fertiser is a far, far more cost effective method of meeting the initial objective. Whether or not the initial objective was a good idea, I'm with @Ken Fabian (as usual).

@Genady opened my eyes somewhat a couple of weeks ago by suggesting I look into the extension of GR into a fifth dimension by Kaluza-Klein which seems to have been a catalyst for QED. A similar extension into a sixth dimension (if I understand correctly) led to Yang-Mills and thence to QCD. What seems odd to me is that having started with GR, why should extensions into yet further dimensions be expected to 'give birth' to a theory of gravity when GR already seems to have that one covered? Is there some reason why Ouroboros must swallow its tail like this? All particles we have ever observed are accounted for by these theories so what more do we need (other than some tidying up of the mathematics perhaps)?

Has physics stagnated for seventy years on this dilemma?

This sermon is uncomfortably close to a social Darwinist way of thinking that is most definitely not born out by my experience of generally amicable relationships with all sections of my local community. The innate and inevitable hostility you postulate just isn't there.

I think your rather over-egging the cake here. A new nephew joined our extended family nearly a year ago, and it's given me the opportunity to see how his reaction develops to not only the only non-African face in the compound, but quite possibly the only white face in a local community of maybe 25,000. Whenever I emerge from my man=cave, his attention is immediately drawn in a way that's immediately obvious to the rest of the family and a source of great amusement as his eyes follow me around the room. He obviously perceives me as different to other family members, and although there's undeniably some element of anxiety there, curiosity dominates. I've seen similar trends with his elder siblings and I've no doubt that in two or three years he too will be regularly visiting the 'troll's lair' to watch my latest Minecraft creations take shape, and ask me for the umpteenth time how to build Iron Golems. A simple common interest on which to bond. He will not be harbouring deep-seated primitive hatreds against fair-skinned people since these only develop if given cause and we as a family shall not give them cause. Indeed, in the near quarter century I've spent here, I've experienced no significant racially-motivated antagonism from anyone in the community. In stark contrast to the frequent abuse directed at my wife by both individuals and bureaucracies when she spends time in the UK. So no. I don't believe you can partially excuse racial hatred as being a natural urge to be overcome by reason..It's embryonic source in nature will only manifest and deepen if nurtured to do so. I've only to watch a Youtube political news clip from the UK or US to see that nurturing in action.

7/8 I guessed +4 hours for St Petersburg.

Depends what you mean by 'overall homogeneity'. If this includes the assumption that your cross-linked product has a uniform molecular weight with exactly the same degree of cross-linking across all particles, then at least in the general case, I see no guarantee of that. Furthermore, I'd tend to view this as a multiphase mixture rather than an ideal fluid. It's more of a dispersion of solids in a liquid medium and what would the viscosity of that solid phase actually mean? But I'm straying a fair bit outside my field here. Perhaps @exchemist or @John Cuthber could add a more expert chemist's perspective.

It will heavily impact whether your software's predicted homogeneity is realistic, utter nonsense or any point between those two extremes. Really. If you're wondering what could possibly go wrong, just think 'lumpy gravy'. Bottom line is that software simulators are no substitute for laboratory work and pilot plant tests however much employers may wish that they were.

Many viscosity models for mixtures employ terms that resemble in form those that characterise entropy of mixing. So if your model indicates a homogenous viscosity, it implies that the entropy is also homogenous which is as good an indicator of complete mixing as you could wish for. You will be on fairly safe ground when dealing with say mixtures of liquid alkanes where the components are fully miscible in all proportions and where much of the research on this subject has been focussed. Don't rely on it for say a suspension of cellulose fibres.

In the absence of any explanation of how Ansys attempts to solve the advection equation in particular, then how can we be expected to judge how reliable it is?

How about Coulomb force? It is so similar in form to Newtonian gravitational force that one wonders whether it too is a fiction. Is spacetime possibly also configured to allow charge to propagate along some electromagetic geodesic as does momentum in a gravitational field? I'm sure this is an idiotic question in a sense, but I'm prepared to endure the humiliation of an informed response.

This is very good. How's this for low-loss compression? On a human level science can never compete with this. For those who think it can, the closing stanza of another poem springs to mind:

In my defence, I would suggest that there is a certain selection bias at play. I tend not to photograph those individuals I didn't notice.

In the absence of a response maybe I can add my further thoughts. If this effect gives rise to six distinct forms of hitrogen molecule (5 para, 1 ortho) and they distribute evenly at equilibrium, then surely this must contribute ln(6) R = 14.9 JK-1mol-1 to the standard entropy? However when I check references like Chem.libretexts the standard entropy for nitrogen (S0 = 191.6 JK-1mol-1) doesn't appear anomalously high. Compare with O2 (S0 = 205.1 JK-1mol-1) & CO (S0 = 197.7 JK-1mol-1). Puzzling.

This is also true of many engineering disciplines where we tend to have greater exposure to more empirical formulae. This helps reinforce the impression that the science is data-driven: that the formulae are more of a convenient shorthand for expressing correlations observed in large to very large datasets. Sometimes the correlation is so clear and simple to suggest an obvious underlying mechanism that further data may confirm. But the rooting remains firmly in real observation. I don't see how lapsing into solipsism and questioning that reality is of any help to anybody.

Would monopoles have anti-particles?

Over the last 25 years or so it has been highly amusing to see German heavy rock band Rammstein quietly but consistently appropriating and repurposing right-wing iconography to serve politically progressive purposes. It's a brilliant strategy. Absolutely immune to any accusation of 'wokeness'. But at the cost of being somewhat challenging to those who want nothing to do with that particular kind of iconography. For those of a nervous disposition, the title means exactly what you think it means so feel free not to view if you think you'll be offended. Though by doing so you'll miss some beautiful wind band intros and outros by members of the Dresdner Staatskapelle Orkester which would be a pity.

I'm not aware of there being such a marked anomaly in nitrogen specific heats as for hydrogen. Perhaps it's something to do with the relative atomic masses. Without knowing the dU and transition temperature values, it's hard to evaluate. But it should appear much like a gradual phase change over some specific temperature band. My guess is that the effect is rather small otherwise it would be cropping up in the literature quite frequently.

There are (as usual) many good points in what you say. But I'll counter with a question. Why when meteorology was quite a long established discipline, did it require a steam engineer, Guy Callendar, to ring the alarm bells? The key is I think summed up in this quote from https://www.thermopedia.com/content/796/. In other words, in order to design an efficient furnace, one needs a very clear understanding of the emissivity of CO2. A level of understanding that wouldn't be at all common in other disciplines (such as meteorology). Combustion engineering was a fairly mature technology by the 1930's and it would not have required a genius among them to extrapolate the behaviour of CO2 inside the furnace out into the wider environment. Indeed, various individuals had been doing this over the previous century or so. Callendar was simply the first to collect a reasonable dataset of historic climate records that indicated increasing anthropogenic warming correlating with an understanding that was largely concentrated within the energy and utilities sectors of industry. I guess that some meterologists at the time might have had there noses put out of joint at being upstaged by a mere engineer.

Sometimes I just can't hide my natural flair for colour coordination 😋

Actually, I enjoy cooking for myself very much and aren't too bad at it. Here's one I did earlier: I'd caught the yellowfin that morning. The sauerkraut, lime pickle and pickled onions are all homemade from local produce, other than the spices. And the darjeeling of course. The big plus of preparing your own food is that you can make whatever you want regardless of anyone else's styles and tastes. This one's a real mish-mash of different traditions so you'd be hard pressed to find anything like it on a regular menu. But you do need to dip into other styles and traditions sometimes whether to extend your repertoire, or just for the simple enjoyment of it.

Check entropy of mixing. The slightest difference in particle properties produces a significant step change in entropy irrespective of the degree of difference. It's this aspect that got me thinking about these spin isomers in the first place. Again: Gibbs' Paradox.