### Tech Briefs

One-Way Coupled Fluid-Structure Interactions

In many FSI analyses the deformation of the solid is so small that its influence on the
fluid flow is negligible. Therefore, only the fluid stresses need to be applied onto the
structure and no iteration between the fluid model and the solid model is necessary. We
illustrate the one-way coupling FSI capability of ADINA using the already familiar manifold
model shown above and presented in the September 28, 2004 News.
The fluid inside the manifold is oil (ρ = 1000 kg / m^{3};
μ = 0.2 Pa·s) with Re = 2000. The pressure at the three
outlets is 1 MPa. The manifold is made of steel pipes
(E = 200 GPa; ν = 0.3) with a thickness of 2 cm. The fluid mesh
has 648,684 tetrahedral elements (2,594,736 equations) and the solid model was discretized
with 20,017 4-node shell elements. The fluid model was solved first, and then the solid
model was solved applying the fluid stresses obtained in the fluid solution.
It is worth noting the difference between the solid and fluid meshes. ADINA automatically performs all the interpolations necessary
to apply the fluid stresses in a consistent manner onto the solid
structure,
so that there are no restrictions on the type of elements and meshes used in the solid and fluid
models.

The animation below shows the displacements, magnified 50 times, on the solid structure. In the next figure, the effective stresses on the structure are shown. Since the maximum effective stress is 350 MPa (yield stress is 207 MPa), a bilinear elasto-plastic material model was used for the steel
manifold.