FSI the intelligent way

Not just the physics; a different level of ease of use and productivity through the Integral approach

ICSM++, ICFD++ and MetaFSI provide a general Fluid Structure Interaction capability. MetaFSI utilizes different grids suitable for each computational domain and ensures accurate transfer of loads from the ICFD++ boundaries to the corresponding ICSM++ boundaries. The structural mesh need not be exactly co-located with the fluid mesh. MetaFSI’s mesh morphing capability has been developed and evolved using real-world test cases and provides a robust mesh morphing scheme. Each user interface is specifically designed to allow the user to set up a complex multi-physics problem in a simple way.

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  • What is MetaFSI?
  • Why MetaFSI?
  • Features
  • Capabilities
  • Validation

MetaFSI is:

  • Metacomp’s in-house Fluid-Structure Interaction (FSI) suite of tools
  • Designed specifically to work seamlessly with ICFD++ and ICSM++ to carry out FSI analysis
  • Also works with MSC Nastran

Why MetaFSI?

  • Easiest way to integrate a tightly coupled fluid-structure interaction with CFD++ and CSM++ or external code like MSC Nastran
  • Advanced User Interface easily allows transfer of loads and displacements between ICFD++ and ICSM++ / Nastran
  • Fast setup and testing of mesh morphing
  • Morph the CFD++ mesh based on received CSM displacements

MetaFSI

is a key component in enabling tightly coupled fluid-structure interaction with ICFD++ and ICSM++ (or MSC Nastran)

Primary functions of MetaFSI

  • Transfer loads and displacements between ICFD++ and ICSM++/Nastran
  • Setup and test mesh morphing
  • Morph the ICFD++ mesh based on received CSM displacements
  • MetaFSI is available in two versions

MetaFSI built-in to ICSM++

  • Automatically activated when selecting the FSI option in ICSM++
  • Appears as a new page in ICSM++ AUI environment
  • Enables tightly coupled FSI setup process with easy and consistent user experience

MetaFSI stand-alone version

  • Enables users of MSC Nastran to run FSI analysis by coupling with ICFD++
  • Nearly identical capabilities and set-up process as the built-in version

Advanced User Interface

  • Part of Metacomp’s Integral Computational Multi-Physics (ICMP) framework
  • Single environment for mesh generation, CFD, structural analysis and visualization of results
  • Design elements and UI consistent between all ICMP-based products
  • Intuitive and simple guided problem set-up process
  • Powerful and user-friendly at the same time!

Mesh morphing

Propagate displacements at the wetted boundaries into the ICFD++ volume

Compute 3D displacements by interpolation:

  • 3D Radial Basis Function (RBF) based interpolation functions
  • Robust algorithm using RBFs with global support

Move grid points using computed interpolant

  • Substantially reduce computational effort by limiting active morphing region
  • Grid points outside user-defined active morphing region remain stationary
  • E.g.: Morphing grid points in far field regions can be insignificant

Works with dissimilar meshes

  • Allows for non-matching ICFD++ and ICSM mesh surfaces
  • Exchange CSM displacements, CFD loads by nearest-neighbor interpolation
  • Transfer preserves total load and center of pressure
  • Use AUI to visualize and inspect degree of collocation between grids

Works with ICFD++ and ICSM++ / MSC Nastran 

For ICSM++

  • Integral advanced user interface (AUI)
  • Visualize ICSM++ and ICFD++ boundaries
  • Force and moments transfer
  • Utilizes rotational DOF
  • Displacement relaxation is available
  • Normal modes based coupling

For MSC Nastran

  • Stand-alone AUI
  • Only forces transfer
  • Roatations not used
  • No displacement relaxation options
  • SOL400 only

Modal analysis

  • Pre-computes morphed mesh for each mode shape
  • Constructs linear combinations of these meshes for each time step
  • Significantly reduces computational cost for transient analyses
  • Mode automatically activated when running modal analysis in CSM++
  • Benefit of the ICMP approach!

Additional capabilities

  • Independent physics options in CFD++ and CSM++/ MSC Nastran
  • Implicit (sub-iterations) or explicit coupling
  • Serial or parallel mesh morphing
  • Sockets-based communication between CFD++ and CSM++
  • Load transfer from surfaces to lines (e.g.: wing surface to beam model)

 

  • HIRENASD Model
  • FSI2 Benchmark
  • HA145 Model
  • Lid-Driven Cavity

HIRENASD Model 

Geometry: 

  • 3-D aeroelastic wing with generic fuselage model
  • Imported into CSM++ from existing NASTRAN model (AePW)
  • Element types: parabolic tetrahedrons, point masses and rigid elements (NASTRAN RBE2s)
  • Material: 18Ni maraging steel
  • Load: Excitation @78.9 Hz by axial forces producing internal force couples
  • Pressure taps at 7 spanwise locations
  • Multiple accelerometers
  • Steady State: M = 0.8, Re = 7 million, α = 1.5o, q/E = 0.22
  • Transient: M = 0.8, Re = 7 million, α = 1.5o, q/E = 0.22, 78.9 Hz excitation, 2.4 mm amplitude at accelerometer 15

Results:

 

Mode Experiment NASTRAN CSM++
1st Bending 26.015 25.550 25.732
2nd Bending 78.635 80.245 80.588
1st Lead-Lag - 106.193 106.991
3rd Bending 166.250 160.349 160.385
4th Bending 245.002 241.995 240.846
1st Torsion 265.885 271.884 268.391

FSI 2 Benchmark Model

Geometry and Results:  

About the model: 

  • 2D numerical benchmark proposed by Turek and Hron (2006)
  • Incompressible laminar channel flow
  • Cylinder is slightly off-center along vertical axis
  • Deflections at the trailing edge compared
  • Requires use of IQN displacement relaxation

HA145 - Subsonic Wing

Geometry:

  • Subsonic 15o sweptback wing - MSC Nastran flutter example
  • Experimental flutter result by Tuovila and McCarty (1955): M = 0.45
  • Nastran doublet-lattice method: M = 0.455
  • ICFD++/ICSM++/MetaFSI:M = 0.475
  • Subsonic wing with sharp edges requires finer CFD mesh

Results: 

Lid-driven Cavity

Model and Results: 

  • Oscillating top wall
  • Very flexible bottom
  • Requires large strain elements
  • Frequencies agree well
  • Some variation in periodic steady state deflection values