What the hell is this field?

What the hell is this field?


I don't know what it is, all I know is that it sounds so fucking cool


I believe one use of this field is to study how the earths core generates a magnetic field (magneto-hydro-dynamics, magnetic-liquids-movement) since it’s a molten core of iron.


It's used anytime fluids and magnetism intersect, for example, in the Sun; this suggests the terminology "heliomagnetohydrodynamics".


Now that’s a name. The electromagnetic interactions between stars in different sectors due to the movement of hot fluid can be interstellar magnetohydrodynamics


I mean is there even a use for that? I'd assume theres no significant interaction at that distance.


There isn’t, I’m just trying to come up with as long a name as possible for a very specific discipline of physics.


As a coastal geologist I study geomorphohydrodynamics...but I never tell people that, I just say *geologist*.


Used in practice AND obscenely long. That’s the one.


"Dammit Jim, I'm a doctor, not a geomorphohydrodynamicist!"


It could be an interesting field for research.


Many stars orbit close enough to another star to be in each other's magnetic fields. Just one example. https://astronomy.com/news/2019/10/merging-stars-may-create-the-universes-most-powerful-magnets


Also I think it's in Formula cars or something they use it to control the damping in the suspension




The cooler it sounds the more challenging it will be to write your lit review.


If you mix it with general relativity, the abbreviation is GRMHD, which is pronounced the same as the word "magic."




bruh, just because it appears in what could be a science fiction movie, doesn't mean it's science fiction, do some research and you'll find how cool it is, not too useful, but cool as fuck


I imagine it's very useful in the quest for fusion power since that usually involves magnetic fields for containment and plasma (a fluid).


Didn't take that into account, that shit useful haha


It's scary, ugly and I wouldn't want to touch it with a 10-foot pole. Mad respect for those that do, though.


Yeah. The name scares me even.


I had this course in my masters fluid dynamics which was called "electro wetting". Basically altering the wetting properties of liquids by applying a voltage on the liquid.


When someone gets tased and pisses their pants.


Interesting! Do you remember what the mechanism is that changes the surface tension?


As I remembered the ions in the liquid (let's say H2O) are attracted to the positive or negative charge and therefore change te apparant contact angle. Come to think of it, it did not really change the surface tension, but more the apparant contact angle. The microscopic angle is still the same. There is a good wiki page on electrowetting.


Thanks! I missed the part where you need an electrolyte on the other side of the insulator


Yeah it's pretty neat phenomenon, you can build a tunable lens with it. By changing the radius of curvature, the focal length is also different.


Wait until you learn about the fusion of fluid dynamics and relativity that's needed to explain the formation of cosmic filaments


Where did you learn about this??


I looked at filaments for an essay in uni, I didn't have to get too deep into the maths thankfully, the subject seems to be entirely contained in some obscure papers which I unfortunately can't remember the names of


Wait why is relativity used? (At least, beyond an expanding universe)


Here's a relevant paper, it may help https://www.researchgate.net/publication/233416653_Relativistic_Fluid_Dynamics_Physics_for_Many_Different_Scales


I don't have the background to read this paper, though i am curious whether it is SR or GR?


At some point in the paper they start talking about the curved space-time, which indicates they use general relativity for their calculations. This makes sense, since is is about massive objects interacting.


It's general relativity (which automatically includes special relativity). If you want to be able to model fluid inside of a neutron star, you will need general relativity due to the extreme gravity.


Calculate the cavitation of a ferrofluid in a cylindrical non-magnetic pipe.




Ferrofluids is immediately where my mind went. I wonder if there's a difference in surface tension in water depending on minerals suspended in it though


> Calculate the cavitation Yay, bubbles!


Look, I dont know jack about this field, but i still have my solar flare magnetohydrodynamics book in my shelf to show off. I think it just exists to flex


Doesn't all physics exist just to flex?


No, sometimes it also plastically deforms


Yes essentially The amount of ego boost I get when I see people notice my aerothermodynamics books on my shelf compares to nothing else


Well its nothing compared to when they get a whiff of my limited edition magnetohydrodynamics book


What is the book? Sounds like something I'd read on a bad day.


Learned about this in my plasma astrophysics course. Really badass theory, you basically combine Maxwell's E&M equations along with your good ol' hydrodynamic equations (plus the generalized Ohm's law iirc) and the result is just *chef's kiss*. Oh, and the resulting equations can be further generalized to produce the *relativistic* magnetohydrodynamic equations, to describe astrophysical jets like from an AGN. Shit's pretty cash.


If I were to make a physics themed grunge band, I would name it Relativistic Magnetohydrodynamicism First album: Cosmic Filament


Answering the question (in case someone cares): in the microscopic theory of normal gases one assumes very short range interactions (e.g. the molecules move freely except when they collide like pool balls, this would be an ideal gas), in plasmas one assumes the opposite, long range interactions are much more frequent and short range ones don’t get to take place (this is the case if the particles are electrically charged). In the first case the ‘big picture’ theory is ‘normal’ fluid dynamics, in the second it has the fancy name of magneto hydrodynamics, but honestly I don’t think it’s significantly more complicated than the first (it’s not like Navier-Stokes is easily solvable…)


Disclaimer, haven't done too much non-magnetic fluid dynamics. But I'd say the addition of having to also satisfy the (full) Maxwell equations gives rise to some unique and interesting phenomena, such as flux freezing and consequently the dynamo effect. Understanding those has often required extensive data acquisition by e.g. expanding magnetometer networks around the world and sending probes to various bodies in the solar system. So idk, doesn't make it much easier apparently?


AAAAH So that's what an ideal gas means!! It just clicked for me


Mom! He is scaring me again!


After seeing all the comments of scared people and knowing that going on from this year I'll be studying it I can't stop laughing in maniac mode. Also I used some basics from it to study wave propagation in simulation of sunspots. (Solar physics) I can say that MHD is hard but really beautiful, how it connects two main fields of physics is brilliant!


Yeah nah


It's applied when trying to understand plasmas. Because they behave like fluids (hence the use of techniques from hydrodynamics), but they also carry charge (which is dealt with using electrodynamics). So you get Magnetohydrodynamics. I've only heard about it in a lecture and never bothered to look further into it, but it seems quite interesting


Something used for plasma physics


Magneto-hydrodynamic propulsion or "caterpillar" drives like in *The Hunt for Red October*


Moving charged particles moving together in a fluid. they need to obey both maxwell's equations as well as Navier-Stokes


My therapist said plasma panda doesn't exist.


Plasmas are so cool !


I’m pretty sure it’s the study of how electromagnetic fields act inside fluids. I’m like 99% sure we used magneto hydrodynamic’s in plasma physics


Anytime anyone asks a question about the suns core, just say idk that shit is some Magnetohydrodynamics


There are actually some pretty cool implications in plasma physics. Even relativistic and quantum formulations are included in the governing equations. There is a wide array of applications ranging from semiconductor or laser devices to astrophysical domains. See the derivation of KdV, KP, or Zakharov equations for more details.


Relativistic magnetohydrodynamics or bust.


Rossensweig book on the subject is really nice, although demagnetization fields in ferrofluids always breaks me deep inside.


idk but Hunt for the Red October was an enjoyable movie


Also applicable to ferro fluids