The Fluid Structure Interaction (FSI) model in FLOW-3D version 10.0 provides a coupled solution to the fluid dynamics as well as solid mechanics. For fluid structure interactions as well as thermal stress evolution, fluid pressures, thermal gradients and body forces contribute to deformations in the solid. The deformations are then fed back into the fluid flow. The fluid computations are performed on a finite difference Cartesian mesh and the strain-stress equations are solved on a Finite Element (FE) body fitted mesh. The user can generate FE meshes for any complex shape, whether produced from CAD geometry stereolithography (STL) files or via FLOW-3D’s geometry input. The FE mesh generator makes use of the standard FLOW-3D Cartesian mesh as the starting point. The shapes of the elements that contain the solid surface then conform to capture the interface of the solid. The FE mesh is generated with little to no input from the user. However, the user has the option of generating elaborate and complex FE meshes.
Local refinement of the FLOW-3D mesh improves the level of details that appear in the finite element mesh.
Plot (a) shows the part as produced by FLOW-3D's stereolithography (STL) file viewer. Plot (b) shows a sample
result of a coarse FE mesh, while plot (c) shows how fine detail can be resolved in the FE mesh by increasing
the local resolution of the containing Cartesian mesh.
Sluice gates on a spillway deform due the hydrostatic pressure from the fluid behind them.
The displacements in the sluice gates are magnified by 50,000 times for visualization.
The elastic properties necessary to solve the solid mechanics problem can be defined as temperature dependent. Flow Science has partnered up with Material Property Database (MPDB) to offer access to thousands of solid materials and their temperature dependent properties. The output variables to analyze the solution to the solid mechanics aspect of the simulations are:
- full stress tensor
- full strain tensor
- deformations in three dimensions
- normal displacement
- volume expansion
- mean isotropic stress
- von Mises stress