Dear Friends
I want to study the flow around cylinders in FLUENT/CFX.
Kindly tell me how to model the flexible cylinder. So far, I was just analyzing the flow around stationary cylinder, but in literature, there is a lot of study on flexible or elastic cylinders. However, I could not find the option to make the cylinder flexible or elastic.
Dear Niaz,
Your question is referred to what is known as Fluid Structure Interaction (FSI) modeling. There are two approaches: (a) 1-way (only fluid affects the solid interface); (b) 2-way coupled (both fluid motion and solid deformation affect each other).
In the first one, you need to compute the flow field as if the solid is rigid and find out the velocity and stress field on the solid surface to proceed to calculate in a second stage the deformation of the solid in the Computational Solid Mechanics solver.
The second approach, is more precise and realistic as it requires the fluid boundaries to update as the solid deforms and therefore, the code has to solve iteratively until it reaches an equilibrium or quasi-equilibrium condition.
In current version of ANSYS-CFD (both Fluent and CFX) this coupled approach can be set up easily via Workbench. In very old versions, perhaps before V5.6, I don´t recall exactly, the coupling had to be done via Fortran subroutines in CFX, but now it´s direct and you just need to prescribe the model flow-stream properly (given that you have the license for ANSYS for Solid Mechanics also of course).
Check this tutorial sequence (1/3 is this and look for more with keyword ¨Two-way FSI with ANSYS¨):
https://www.youtube.com/watch?v=jNjYuw9mznA
I hope it helps.
Regards,
Luis
Dear Niaz,
Your question is referred to what is known as Fluid Structure Interaction (FSI) modeling. There are two approaches: (a) 1-way (only fluid affects the solid interface); (b) 2-way coupled (both fluid motion and solid deformation affect each other).
In the first one, you need to compute the flow field as if the solid is rigid and find out the velocity and stress field on the solid surface to proceed to calculate in a second stage the deformation of the solid in the Computational Solid Mechanics solver.
The second approach, is more precise and realistic as it requires the fluid boundaries to update as the solid deforms and therefore, the code has to solve iteratively until it reaches an equilibrium or quasi-equilibrium condition.
In current version of ANSYS-CFD (both Fluent and CFX) this coupled approach can be set up easily via Workbench. In very old versions, perhaps before V5.6, I don´t recall exactly, the coupling had to be done via Fortran subroutines in CFX, but now it´s direct and you just need to prescribe the model flow-stream properly (given that you have the license for ANSYS for Solid Mechanics also of course).
Check this tutorial sequence (1/3 is this and look for more with keyword ¨Two-way FSI with ANSYS¨):
https://www.youtube.com/watch?v=jNjYuw9mznA
I hope it helps.
Regards,
Luis
Another simple approach, if you are not keen on FSI is moving mesh approach. Create good structure mesh using Blocking technique. would recommend to start with 2D mesh for trial and apply small steps to move your boundary during your computation. same algorithm can be applied for complex 3D mesh. refer below discussion on Piston moving Dynamic mesh approach.
http://www.cfd-online.com/Forums/star-ccm/75483-moving-piston.html
you may study this
http://pubs.rsc.org/en/content/articlelanding/2010/lc/c003627g#!divAbstract
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