Minimal Surface shape with gravity

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Discussion Overview

The discussion revolves around the characterization of minimal surfaces influenced by gravity, specifically exploring the shape of a hammock. Participants examine the mathematical formulation of the problem and the potential solutions, including comparisons to known shapes like catenaries.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes minimal surfaces as representing the "shortest path" in terms of surface shapes and proposes a mathematical model incorporating gravity.
  • The equation of motion derived from the Lagrangian is presented, with a claim that it may have non-unique solutions similar to other minimal surfaces.
  • A specific solution identified is a cone, represented by the equation z = √(x² + y²), while a proposed solution of a "2-d catenary" is stated to not work.
  • Another participant suggests that engineering analysis methods can be applied to problems involving sheets of material with physical properties, indicating that distortion requires stretching.
  • A request for sources on engineering analysis methods is made, indicating interest in further exploration of the topic.
  • A link to a Wikipedia page on plate theory is provided as a resource for further reading.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of certain solutions and methods, with no consensus reached on the best approach or the validity of specific solutions.

Contextual Notes

The discussion includes assumptions about the physical properties of materials and the mathematical formulations used, which may not be universally applicable without further context or clarification.

Who May Find This Useful

Individuals interested in minimal surfaces, mathematical modeling in physics, engineering analysis of materials, and those exploring the intersection of theoretical and applied mechanics may find this discussion relevant.

DuckAmuck
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Minimal surfaces are sort of the "shortest path" but in terms of surface shapes.
So I figured I could characterize the shape of a hammock by adding the influence of gravity, much like you can get the shape of a catenary cable (y=cosh(x)).

The equation of motion I get from the Lagrangian is:
z_x^2 + z_y^2 + 1 = z ( z_{xx} (z_y^2 + 1) + z_{yy} (z_x^2 +1) - 2 z_x z_y z_{xy} )
where z is the height of a point on the surface mapped to (x,y).

Of course, this is likely to have non-unique solutions just like other minimal surfaces.
One of the solutions I found is a cone:
z = \sqrt{x^2 + y^2}
What does *not* work as a solution is a "2-d catenary", which is what I initially suspected as solution
z = cosh(x)cosh(y)
Anyone else attempt this kind of problem? What were your findings? I'm basically just plugging things into the equation of motion and seeing if they work.
 
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You can do these types of problem for sheets of material with real physical properties using standard engineering analysis methods .

No initially flat sheet with edge restraints can distort into any other shape without some stretching of the material .
 
Would you mind linking me to a good source for this kind of engineering analysis methods?

Nidum said:
You can do these types of problem for sheets of material with real physical properties using standard engineering analysis methods .

No initially flat sheet with edge restraints can distort into any other shape without some stretching of the material .
 

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