An elastic membrane and wall model has been developed to provide a limited Fluid-Structure Interaction (FSI) capability in FLOW-3D. In the model, deformation of an elastic membrane or an elastic wall impacts the adjacent fluid flow, while fluid pressure, in turn, affects the deformation. These interactions are described in the code in a fully coupled fashion.
The main assumption of the model is that the deformations are small, i.e., the deflections are much smaller than the size of the deforming object (for elastic membranes) or the characteristic lengths of fluid flow and wall thickness (for elastic walls), allowing for a few useful simplifications. The geometries of membranes and elastic walls are assumed to be time-invariant, while the effects of their deformation on fluid flow are described with volume sources and sinks distributed along the fixed fluid-structure interface. With the further assumption that the pressure force is uniformly distributed on the membrane surface, analytical solutions rather than structural analysis algorithms are used to determine the membrane deformation.
There are many potential applications for the model in microfluidic systems, e.g., chemical analysis systems, medical microdosage systems and inkjet devices. The model can be used to simulate flow in piezoelectric valveless pumps which convert membrane vibrations into a pumping action. The model can also be used to simulate droplet formation for piezoelectric inkjet printheads where a membrane or an elastic tube deforms under the force of a piezoelectric actuator to produce a droplet of ink.