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Plotting ellipsoids with R

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New article: Generating polydisperse periodic RVEs containing ellipsoidal particles (part 1) http://www.parresianz.com/r/periodic-rve-with-ellipsoids/

I'll post the rest on the series on this comment thread because my articles are not showing up on the imechanica RSS feed.

-- Biswajit

Part 4 of article on periodic RVE generation.  http://www.parresianz.com/dem/periodic-rve-with-ellipsoids-part-4/

New article: Visualizing ellipsoids with VisIt and ParaView (a hack) : http://www.parresianz.com/dem/ellipsoids-in-visit-and-paraview/

-- Biswajit

Guess your concern here is mainly about visualization, but if you would allow me an idle musing on the side:

If the surface of a hollow ellipsoid (i.e. one which is not a sphere) emits a force-field (say, one that follows the inverse-square law), then, the net force per unit surface area at any point interior to the ellipsoid (other than the center) would be a function of the orientation of that surface. ... Due to symmetry, the net field at the center point would be zero at any orientation, be it a sphere or an ellipsoid. ... But coming back to the force per unit area, one that varies with the orientation of the surface is precisely what we want in order to reach the concept of stress, don't we?

... Just an idle musing, that's all... (Someone must have already written a journal paper that at least in part covers this idea.)

Best,

--Ajit

 

Yes, my concern is mostly with recording solutions to issues that I have run into.  I particularly like the one in the latest article.

Also, I have no idea what you are talking about in your comment; probably because I find it hard to understand things without pictures or equations as illustration.

-- Biswajit

Hmmm...

I googled and found that:

(i) A lot of people from Laplace to Chandra have studied the problem of gravity (a force field having an inverse-square law) produced by an ellipsoid; e.g. see here [^] or here [PDF ^]. However, they seemed to have been focused on a dense ellipsoid, whereas what I was just idly musing about was a hollow one (i.e. an ellipsoidal shell). [Yes, my hunch turned out right; there are many papers on the broad topic as such.] The problem for the hollow sphere was solved by Newton himself [^]. But, apparently, not for a hollow ellipsoid.

(ii) As I just found out, someone else other than me had thought of the problem; see here [^].

(iii) Further, I was also wondering if for the hollow ellipsoid, gravity had a law of the form: F = r^{n}, where n is not equal to -2.

Anyway, forget about it. There are no [further and relevant] pictures. Sorry if I ended up distracting you.

Best,

--Ajit

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