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deformation of a moving submerged object

Posted Jun 12, 2012, 1:18 a.m. EDT Fluid & Heat, Computational Fluid Dynamics (CFD), Mesh, Studies & Solvers, Structural Mechanics Version 4.2a 2 Replies

Saman Kumar
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Hi All,

I'm a beginner of the Comsol. I have to model the deformation of a submerged flexible object. I use FSI model, but I'm wondering that the motion and deformation of this circular object can be modeled or not. I f any one have a clue. please help me. so far I developed a model to analyse the deformation of an fixed object, but it does not show any deformation.
Please help me.

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2 Replies Last Post Jun 12, 2012, 5:38 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Jun 12, 2012, 1:46 a.m. EDT
Hi

first I would advise to read carefully a few times the different docs, as FSi is already complex physics and there are many things to learn.

a few tips:
use Parameters for contant values and not Variables, use variables for things that might change during the simulation or depend on the simulation results

Point constraints are tricky, try using as far as possible boundary constraints (your fixed "point" replace it by a small circle and fix the boundary of the circle

You are in 2D, be aware that this means flow between two plates 1 meter deep (nothing wrong with that but its not 100% as a round "tube/pipe"

Mesh, try the default physics meshing, as yours has no boundary layer and will not easy the convergence of the solver

You have noslip conditions, this mans that the flow has "0" velocity at the walls, but you impose a flat inlet velocity, its better to use a parabolic velocity profile or a laminar inflow

turn on the "defomration" node to see your "solid" deform

Check the Reanold cell number, just to be sure you are in a good laminar regime (the case I see but it's good practice anyhow)

--
Good luck
Ivar
Hi first I would advise to read carefully a few times the different docs, as FSi is already complex physics and there are many things to learn. a few tips: use Parameters for contant values and not Variables, use variables for things that might change during the simulation or depend on the simulation results Point constraints are tricky, try using as far as possible boundary constraints (your fixed "point" replace it by a small circle and fix the boundary of the circle You are in 2D, be aware that this means flow between two plates 1 meter deep (nothing wrong with that but its not 100% as a round "tube/pipe" Mesh, try the default physics meshing, as yours has no boundary layer and will not easy the convergence of the solver You have noslip conditions, this mans that the flow has "0" velocity at the walls, but you impose a flat inlet velocity, its better to use a parabolic velocity profile or a laminar inflow turn on the "defomration" node to see your "solid" deform Check the Reanold cell number, just to be sure you are in a good laminar regime (the case I see but it's good practice anyhow) -- Good luck Ivar
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Jun 12, 2012, 5:38 p.m. EDT
Yes it can be modeled. Your model is actually deforming but very little since the pressure is much lower than Young’s modulus. The point constraint you have is problematic as Ivar described. It also does not remove all 3 rigid body modes in a 2D analysis, so add more constraints. Also for better accuracy and ease of convergence include a boundary layer mesh.

Nagi Elabbasi
Veryst Engineering
Yes it can be modeled. Your model is actually deforming but very little since the pressure is much lower than Young’s modulus. The point constraint you have is problematic as Ivar described. It also does not remove all 3 rigid body modes in a 2D analysis, so add more constraints. Also for better accuracy and ease of convergence include a boundary layer mesh. Nagi Elabbasi Veryst Engineering

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