CMM simulation with variable hyperelastic anisotropi wall material properties

[Ione Ianniruberto]

Hi everyone,

I'm working on a project and I want to perform an FSI (CMM) simulation of the aorta.

I would like to set hyperelastic and anisotropic wall material properties, particularly using the Holzafell-Gasser-Odegn costituitive model with two families of fiber. I would like to set different constitutive parameters in three different regions of the aorta specifically: the ascending aorta, the aortic arch and the descending aorta.

Is there a way to include this material description in the simulation? if not is it possible to do something similar with ALE method?

Moreover, here https://github.com/SimVascular/svFSI-Tests at this link a fiber.vtu files containg information about fiber directions are mentioned, however these file are not avaible at the link. Where can I find them?

Thanks for the assistance,

Ione

[David Parker]

HI Ione,

You can create regions with different constitutive models using Domains (see https://github.com/SimVascular/svFSI/bl ... r.inp#L282).


Moreover, here https://github.com/SimVascular/svFSI-Tests at this link a fiber.vtu files containg information about fiber directions are mentioned, however these file are not avaible at the link. Where can I find them


It's not clear to me which fiber files you are referring to. The only fiber files I see are here https://github.com/SimVascular/svFSI-Te ... ve/mesh/P1.

Cheers,
Dave

[Ione Ianniruberto]

Hi thanks for your answer,

so is it possible to define different domains also if I am using the CMM method? Because reading the svFSI_master.inp file it seems that different domains can be defined only if the ALE method is used.

In the CMM instruction I found this instead: MM" or "Coupled Momentum" BC type, then that face will be treated as a linear elastic membrane interacting with the flow. So using CMM it is not possible to define hyperelastic and anisotropic property, right?

Regarding the fiber file, I want to define the wall properties using the constitutive model of Holzafell-Gasser-Odgen. This material definition requires a fiber file: "For this model to be used, two families fibers must be loaded in "Add mesh". Fiber directions may be loaded for some material models. Fiber direction must be stored at the element level using the data array name, "FIB_DIR", in the vtu format. Fiber direction file path:/mesh/fibers_longitudinal.vtu fiber direction file path: ./mesh/fibers_sheet.vtu." (this file is different from the one you tolsd me). I would like to know how this file should be made.

Thanks again,

Ione

[David Parker]

Hi Ione,

so is it possible to define different domains also if I am using the CMM method? Because reading the svFSI_master.inp file it seems that different domains can be defined only if the ALE method is used.

In the CMM instruction I found this instead: MM" or "Coupled Momentum" BC type, then that face will be treated as a linear elastic membrane interacting with the flow. So using CMM it is not possible to define hyperelastic and anisotropic property, right?

Correct, the you will need to use ALE to simulate a vessel with a hyperelastic material model.

Regarding the fiber file, I want to define the wall properties using the constitutive model of Holzafell-Gasser-Odgen. This material definition requires a fiber file: "For this model to be used, two families fibers must be loaded in "Add mesh". Fiber directions may be loaded for some material models. Fiber direction must be stored at the element level using the data array name, "FIB_DIR", in the vtu format. Fiber direction file path:/mesh/fibers_longitudinal.vtu fiber direction file path: ./mesh/fibers_sheet.vtu." (this file is different from the one you tolsd me). I would like to know how this file should be made.

The file given in the Fiber direction file path command is VTK VTU-format file containing a CellData DataArray named FIB_DIR containing 3D vectors defined for each element in the mesh. For cardiac tissues these files are created using some sort of rule-based method (see https://simvascular.github.io/documenta ... -fiber-gen). I'm not sure how to create them for arterial tissue.

Note that you can use the Fiber direction: command to define a constant fiber direction (see https://simvascular.github.io/documenta ... -fiber-gen and https://github.com/SimVascular/svFSI-Te ... /svFSI.inp).

Cheers,
Dave