Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Dissipation constant should be scaled with mass instead of lengths #81

Closed
armantekinalp opened this issue May 11, 2022 · 2 comments · Fixed by #87
Closed

Dissipation constant should be scaled with mass instead of lengths #81

armantekinalp opened this issue May 11, 2022 · 2 comments · Fixed by #87
Assignees
Labels
bug Something isn't working
Milestone

Comments

@armantekinalp
Copy link
Contributor

armantekinalp commented May 11, 2022

Describe the bug
In Elastica dissipation constant (nu) is defined as per unit length and its unit is kg/(m.s). However, this assumes that rods are uniform. However, in the case of tapered rods dissipation constant should also be scaled with the area. Otherwise for two elements that have same velocity but different mass we apply same dissipation force.

How to fix

  1. Define the dissipation constant as 1/s .
  2. In allocate function, scale the user defined nu with element mass and store it.
  3. Remove multiplication by lengths while computing the dissipation forces and torques.

@armantekinalp armantekinalp added the bug Something isn't working label May 11, 2022
@armantekinalp armantekinalp added this to the Version 0.3 milestone May 11, 2022
@bhosale2 bhosale2 self-assigned this May 12, 2022
@bhosale2 bhosale2 linked a pull request May 12, 2022 that will close this issue
@bhosale2
Copy link
Collaborator

bhosale2 commented May 12, 2022

Hi @armantekinalp some suggestions based on changes in elasticapp.

  1. The name of the parameter must first be changed to damping_rate owing to its nature and units 1/s.
  2. Instead of multiplying in allocate by mass, we should set it as it is there, and for velocity and omega multiply by mass and J / e, respectively, when computing damping forces and torques.
  3. A note should be made in the example cases for damping, where we need to rescale these values to match the old implementation effect.

@bhosale2 bhosale2 linked a pull request May 17, 2022 that will close this issue
bhosale2 added a commit that referenced this issue Jun 1, 2022
@bhosale2
Copy link
Collaborator

bhosale2 commented Jun 1, 2022

Closed by #87.

@bhosale2 bhosale2 closed this as completed Jun 1, 2022
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
bug Something isn't working
Projects
None yet
Development

Successfully merging a pull request may close this issue.

2 participants