1. Modelling FSI problems in ANSYS Fluent via UDF

2. Fluid-Structure Interaction (FSI)
A Fluid-Structure Interaction model is needed when:
there are heavy fluid actions on
deforming boundaries
it is not possible to neglect
deformations
phenomena are coupled and it is not
possible to study the problem
separating the structural and fluid
effects
e.g. Hemodynamics FSI problem

3. Benefits of FSI Simulation
Investigate if problems are coupled
Determine global performance difference comparing with the rigid case
Analyze local flow field changes
Analyze structural dynamic behaviour
Structural verification
Investigate if problems are physically stable/unstable and determine transition conditions

4. The Proposed Product
The Product aim is to allow FSI problems simulation entirely within ANSYS Fluent
A dedicated FEM solver has been developed by means of UDF coding as plug in for ANSYS Fluent
Dedicated Graphical User Interface (GUI) and Text User Interface have been developed
The Product has been tested, validated and used to simulate practical and industrial cases

5. Our Strategy New: The product allows to set structure material
More Time Steps ? NO
POST -
PROCESSING
CFD Mesh
CFD Materials
CFD Iterations
CFD BCs
FEM Materials
FEM BCs
Next Timestep
New:
The product allows to
set structure material
properties and constraints
in the ANSYS FLUENT
code.
Convergence ? NO
INITIALIZATION
Remeshing /
Smoothing
Pressures, shear
stresses and
contact forces
Displacements
FEM Mesh is built
FEM Iteration
New geometry
from CFD one

6. Product Features General robust FEM solver implemented
Structural simulations in the range of small and large displacements, including non linear and contact problems
2D model for beams with implicit and explicit FEM approach
3D model for shells structure with implicit and explicit FEM approach
Parallel implementation
Static and dynamic transient analysis
Multiphase and turbulence ANSYS Fluent model
Post-processing with ANSYS Fluent

7. Product strengths High efficiency Very light General purpose
The result is a very light code that leaves almost
unaffected the global CPU time
High efficiency
Very light
General purpose
ANSYS Fluent users oriented
There are no interpolation errors
No other software knowledge is required
Highly customizable for client-oriented solutions, services and consultancy.

8. Graphical User Interface
Dedicated GUI in ANSYS Fluent

9. The CFD point of view
Very often FSI problems are analysed by a structural point of view simulating the fluid with too simplified models
The present approach uses the CFD point of view (ANSYS Fluent users point of view), focusing on how the interaction with the structure influences the fluid behaviour
The CFD user is now allowed to set structure material properties and constraints in order to easily simulate its presence in a very family way
The knowledges of other software packages are not required

10. Example of 3D model for shells structure (1)
FSI Interaction between a rectangular curtain and an air flow in a room.
This is an example in which
because there are heavy fluid actions on the curtain surface
and so it is necessary to consider its deformations
it is not possible to study the problem separating
structural and fluid effects
WINDOW
DOOR
CURTAIN

11. Example of 3D model for shells structure (2)
HW & SW configuration
Hardware:
2 AMD Opteron 2,2GHz Processor
16Gb RAM
Software:
OS Linux Fedora 6
ANSYS Fluent Version
Version: 3ddp
Structural analysis solver used:
Explicit

12. Example of 3D model for shells structure (3)
Case 1:
The curtain has the top edge constrained. It’s moved by the air flow
entering from the window and subjected to its dead load.

13. Example of 3D model for shells structure (4)
Case 2:
In this case the event of failure of curtain support is investigated.
The curtain is pushed by the air flow entering from the window and
it’s free to fall because the top edge constraint is missing.

14. Example of related areas
Hemodynamics and FSI Fluid-Structure Interaction
In this branch of medicine is necessary to consider the interaction
between the flowing blood and the vessels walls in order to investigate
and study many hemodynamics problems.
HW & SW configuration
Hardware:
2 AMD Opteron 2,2GHz Processor
16Gb RAM
Software:
OS Linux Fedora 6
ANSYS Fluent Version
Version: 3ddp
Structural analysis solver used:
Implicit solver working with MSC.NASTRAN solver

15. Example of hemodynamics problem (1)
The following picture represents the model of a Systemic-to-pulmonary
shunt that is a surgical procedure to treat complex congenital heart
defects.
It consists of an interposing tube between the sub-clavian artery and
the right pulmonary artery. In this case
it’s important to analyze the pressure drop across the shunt
which is affected by the blood pressure combined
with the distensibility of the shunt.

16. Example of hemodynamics problem (2)
SHUNT

17. University of Rome Tor Vergata
Contact
University of Rome Tor Vergata
Dept. Mechanical Engineering
Via del Politecnico,1 – Rome, ITALY
Tel: Dr. Marco E. Biancolini