Thinking About Buoyancy and Viscosity

• Buoyancy is dependent on density, but viscosity isn't
• Pressure and Density are what contribute to buoyancy
• Intermolecular forces are what contribute to viscosity
• External pressure also contributes to viscosity, as that's what holds the fluid together. But dynamic pressure may not affect it (I'll need to see)
• Aside from internal pressure due to density, there is atmospheric pressure and gravitational force, and also the normal forces on the sides of the container.

My doubt (which is about intermolecular forces)

My doubt is whether viscosity can be expressed in terms of density just as buoyancy can be. That is, because density should somehow depend on the intermolecular forces, which is the same thing for viscosity.

Density would them be relatable to the degree to which the spacetime bends, with volume being considered too. Perhaps macroscopic spacetime curvature is an added effect of spacetime curvatures of subatomic particles? In that case, the magnitude will remain the same, but the volumetric effect of curvature will vary for this reason.

This seems relatable to my doubt when I wanted to figure out the frequency of a water wave as a function of its amplitude and frequency, before realizing that the speed of the wave was the speed of sound in water, and that's how the wavelength could be determined, which had nothing to do with amplitude.

And this, is further due to intermolecular forces between molecules. So this, is what I wish to learn more about.

What the terms in Bernoulli's Equation are

P = P0 + pgh + 1/2pv^2 (P0 is the "static fluid pressure", and pgh is the "gravitational pressure" and 1/2pv^2 is the "dynamic pressure")

The static pressure P0 should account for the container pressure too (PV=nRT), as without either gravitational pressure or external atmospheric pressure (which will be pushed back against), there is no such state as a fluid. Also you never atmospheric pressure without gravity, as it is what causes atmospheric pressure (unless you're blowing air). In other words, without gravity, you're always separately compressing a fluid into a space.

(I forgot that the pressure can get really low as the heat radiates outwards by the walls of the container..)

Is PV=nRT is an approximation at earth? If so outside these conditions, it could be better modeled by Van der Waals forces or by taking into account the Compressibility Factor.

But I think no, because P = nRT/V, V is same everywhere, and n and T determines the Pressure in Vacuum.

For more thoughts on this see Thinking of Fluids Without External Forces.

Container pressure doubt (cleared above too)

I'm confused by how the container pressure is measured

I know A1v1 = A2v2, and with this, we can calculate the velocity of air leaving a bottle when it is opened in space, because without gravity and external pressure, the pressure inside the bottle is 1 atm, since we didn't push the air further when the bottle was closed while at earth. But again, the pressure in the bottle usually radiates outward if the surroundings are cooler, since heat is just electromagnetic field flows.

But in case of manually pumping air, I guess we'll use PV = nRT. Oh yeah, just remembered it while writing!

Arrangement of particles affecting macroscopic effects

Different arrangements of the same charged particles can have a different close range effect (influencing the chemistry, for example, by hybridization of orbitals and thus generated dipole moment). However, the net effect is same outside the sphere of influence if you apply Gauss's law.

Perhaps the field is distorted in the shortest distances from their origin, and it has an effect as it propagates away too. But my mind doesn't compute it right now.

But nevertheless, this is an important idea to think about. Sometimes close range effects are nulled, and at other times, long range effects are nulled.