Fluid Structure Interaction modelling is classified into two types,

  1. Monolithic approach
  2. Non-partitioned approach

Let us look at the various other approaches to model FSI.,

  1. Body fitted method
  2. Immersed boundary method
  3. Mesh free method

One other way to look at the classification is method of modelling the fluid-structure interface,

  1. Strong method (conformal meshes)
  2. Weak or Nitsche method (non-conformal meshes)

😶 I have been using the monolithic + boundary-fitted + fully coupled with quasi-direct coupling

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Fluid mechanics often focuses on studying fluids within a specified domain, unless the importance lies in a tracer particle, such as in drug distribution. When conducting fluid dynamics simulations, we typically ignore the details of the fluid that exits the domain. However, this is not the case with solids, as they do not undergo significant deformations or flow. Hence, studying solid mechanics using eulerian approach is vague.

One possible way to model a solid material is using the lagrangian domains. Solids when modelled in lagrangian framework, move with the material and the mesh deforms along with the material. However, when a structure interacts with a fluid, we need to use a different approach called ALE (Arbitrary Lagrangian-Eulerian) framework. The ALE framework is a combination of both Lagrangian and Eulerian approaches, which allows us to model the deformation of the mesh along with the material, while also allowing the fluid to flow in and out of the domain. This approach is commonly used in fluid-structure interaction problems, where the deformation of the solid affects the fluid flow and vice versa.

In ALE we model fluid solid interaction as follows,

  1. We solve mesh motion problem and move the mesh. (mesh motion problem)
  2. Now, we solve fluid solid problem on the deformed mesh. (moving domain problem)

In ALE, the mesh motion field is simply displacement of solid in solid domain, but is is different in fluid domain. Mesh motion in fluid domain is not integral of velocity field.

Mesh motion in fluid domain does not make any physical sense. But it does in mathematical sense.

In mathematical sense, it is like providing convection effects to fluid in Eulerian formulation. [sentence unclear]