this post was submitted on 04 Jul 2023
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Fluid Mechanics

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Hi all! I defended my Ph.D. thesis back in 2019 and I also served as the creator and moderator for the subreddit r/FluidMechanics for a long time. I think with that I have gathered enough experience and courage to answer some of your queries. Some broad topics that I can answer questions on are:

  • computation fluid mechanics
  • scientific programming and HPC
  • nonlinear shallow water equations
  • statistical description of turbulence: spectra, energy budget etc.
  • experimental methods: PIV
  • stratified turbulence
  • academia
  • navigating your career pre- and post-Ph.D.

Ask away!

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[–] [email protected] 1 points 1 year ago (1 children)

For geophysical CFD, what are typical values you deal with?

  • Viscosity
  • Density
  • Velocity
  • Reynolds number
  • Simulation timestep
  • Total simulation elapsed time
  • Total number of simultaneous unknowns solved for
[–] [email protected] 2 points 1 year ago (1 children)

There are two kinds of geophysical flow studies one can do. 2D simulations where you use models like shallow water equations. Then you deal with

  • Velocity
  • Reynolds number (which implies some viscosity)
  • Froude number (or gravity)
  • Rossby number (or Coriolis force from Earth's rotation)
  • Total energy (so you know when it is in a statistically steady state)
  • Density only if you add many layer
  • Boundary conditions (only if it matters, can be avoided)

You can also do a 3D simulation, but often we use the Boussinesq equations, in which density is approximated as a passive scalar.

This is only the setup, but there is a rich set of phenomena one can aim to simulate with.

[–] [email protected] 1 points 1 year ago (1 children)

So are you treating the Earth's crust as a shallow fluid layer? Or the mantle underneath? I would think the mantle is too thick for shallow water equations.

[–] [email protected] 1 points 1 year ago

Usually for the troposphere or even the atmosphere and the ocean this can be a good model. As you said, I doubt if it can be used to represent lava flows under the earth - something a geologist would know and I am not one. 😀