Defining local mechanical properties

[marisa bazzi]

Hey,

My question is about defining/inputting properties for the wall in FSI. The way it is done now, we use a single set of parameters to define the mechanical properties for the entire domain. Is there a way where I could input the mechanical properties for each mesh element, or Gauss point, therefore creating a more heterogeneous character for the tissue?

Thanks,
Marisa

[Vijay Vedula]

Hello Marisa,

svFSI allows you to input multidomain properties. For example, you can create multiple domains in your mesh by tagging elements with a domain ID and export them as a vtp or vtu file. The file should have a element variable named as DOMAIN_ID and should be of integer type. You can then load the domain file into svFSI using the keyword "Domain file path" in the "Add mesh" section as,

Code: Select all

Add mesh: msh {
   Mesh file path (vtu): mesh/mesh-complete.mesh.vtu
   Add face: epi_base {
      Face file path (vtp): mesh/mesh-surfaces/epi_base.vtp
   }
   Add face: epi_mid {
      Face file path (vtp): mesh/mesh-surfaces/epi_mid.vtp
   }
   Add face: epi_apex {
      Face file path (vtp): mesh/mesh-surfaces/epi_apex.vtp
   }
   Add face: endo_lv {
      Face file path (vtp): mesh/mesh-surfaces/endo_lv.vtp
   }
   Add face: endo_rv {
      Face file path (vtp): mesh/mesh-surfaces/endo_rv.vtp
   }
   Domain file path: mesh/domains.vtu
}

The above example is for a heart which has three domains in the myocardium - endocardial layer, mid-myocardial layer and epicardial layer, each one tagged with a domain ID ranging from 1-3 varying smoothly across the thickness of the heart. Later, you can set properties for these domains in the equation section as,

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Add equation: CEP {
...
   Domain: 1 {
   < domain 1 properties >
   }

   # Myocardium
   Domain: 2 {
   < domain 2 properties >
   }

   # Epicardium
   Domain: 3 {
   < domain 3 properties >
   }
...
}

However, this method works for less than 32 domains in your model. If you wish to prescribe a more smoother, nodal level variation of tissue properties, svFSI allows you to do for the coupled-momentum-method problem alone (CMM). It is provided as input as,

Code: Select all

Add equation: cmm {
...
   Variable wall properties: wall {
      Wall properties file path: svFSI_wall-properties.vtp
   }
...
}

where, the the code looks for properties such as elasticity modulus and thickness in the vtp file.

This feature is not available for FSI but can be easily added if we understand your problem needs. The reason is that, for FSI, one can also simulate complex material models and such a local level variation of properties is generally not studied or available readily.

Hope this helps.

Thanks,
Vijay

[Tanmay Shidhore]

Hi Vijay,

Is there a tutorial project/documentation available on multi-domain meshing? Thanks.