Analytical and Numerical Investigation of the Fluid Structure Interaction of an Elastic Beam in a Water Channel

The interaction between fluids and solids is becoming increasingly important in the design and analysis of machines, buildings and systems. Due to the fluid-mechanical phenomenon of turbulence and the associated flow and vortex shedding, the fluid structure interaction must be considered, for example, in aircraft wings, civil engineering (e. g. television towers or bridges), the rotor blades of wind turbines or in the field of sensor technology. Due to the increasing computing power, increasingly complex tasks can be calculated with the help of numerical simulations.

In this paper, a plastic plate has been defined as test case and has been analyzed in different ways with the methods of the fluid structure interaction (FSI), i. e. with analytical, numerical and experimental approaches.  For this purpose, the plastic plate has been fixed on one side in a water channel and the flow around it and the plate deflection have been measured. The deformation of the plate due to the flow load around it has been analyzed for varied flow velocities.

First, the plate deformation has been estimated based on the analytical equations from structural mechanics and an assumed stagnation pressure on the plate surface. Additionally, the drag coefficient from experimental data of the literature was used to estimate the force on and the bending of the plate. Then two numerical simulations with different FSI coupling methods have been performed with Ansys Workbench 2020 R1. On the one hand, a one-way coupling analysis has been performed in which the pressure field was calculated from the CFD simulation and then transferred to the mechanical analysis. On the other hand, a two-way coupling computation has been performed, which also takes transient effects into account. For this purpose, the flow field and the pressure field have been exchanged iteratively between the fluid and the mechanical solver. This coupling approach is general and corresponds to reality since large deformations and non-linearities are considered. However, this approach always requires a very computation intensive, non-stationary calculation. Finally, experimental measurements have been conducted at the water channel at the Laboratory of Fluid Mechanics and Turbomachinery at Coburg University of Applied Sciences and Arts. The deformation of the plastic plate has been determined using an optical measuring method.

The results obtained from these parameter studies have then been evaluated and compared in order to determine the accuracy of each analysis methodology. The elaborated results have been discussed and analyzed in detail.