How to Calculate the Radii of Curvature for a 3D Flexible Chain?

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Discussion Overview

The discussion revolves around calculating the radii of curvature for a 3D flexible chain, specifically a polymer chain, using known coordinates in three-dimensional space. Participants explore methods to extend curvature calculations from 2D to 3D, addressing challenges and proposing potential approaches.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant seeks guidance on calculating the radius of curvature for a 3D flexible chain using known x, y, and z coordinates.
  • Another participant questions the clarity of the initial request regarding extending the concept of radius of curvature to three dimensions.
  • A reference to curvature of space curves is provided, suggesting a potential resource for understanding the topic.
  • The original poster clarifies their problem by specifying they have six points in 3D space and proposes using sets of three points to draw circles that approximate the curvature.
  • The original poster expresses uncertainty about how to derive a circle from three points in 3D space that lie in the same plane.
  • Participants are invited to share alternative methods for computing curvature in this context.

Areas of Agreement / Disagreement

The discussion remains unresolved, with participants expressing different levels of understanding and clarity regarding the problem. Multiple approaches to calculating curvature in 3D are suggested, but no consensus is reached on a specific method.

Contextual Notes

Participants have not yet established the necessary mathematical framework or assumptions for calculating curvature in three dimensions, and the discussion lacks specific definitions or methods that could be universally applied.

chandan
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Dear all,

I was wondering how the radii of curvature can be calculated of a flexible chain (polymer chain). I have the x,y and z values of the polymer chain. For a 2D chain, I can calculate the curvature radii (http://www.intmath.com/applications-differentiation/8-radius-curvature.php). I am unable to extend it to 3D. Any help or guidance is appreciated.
 
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It's not clear what you mean when you want to extend radius of curvature to 3D.
 
Thanks for response SteamKing and micromass. Sorry for the unclear post.
Let me pose the problem in a little different manner.

Suppose, I have 6 points. Its coordinates x, y, and z are known. Say, (x1,y1,z1), (x2,y2,z2), …, (x6,y6,z6).
The aim is to compute its curvature.

One possible way, I can think is to consider the 3 points, and draw a circle that closely passes through these points. And then draw a circle for the next 3 set of points.

Now, these 3 points are lying in a plane. And I have x, y and z coordinates of these points. I do not know how to obtain a circle from these points. The circle also lies in the same plane.
Any suggestion on these would be very helpful.

If anyone can share other ways to compute the curvature, it would be fruitful.

Chandan
 

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