Buoyant Rods for Guiding Fish Past Turbines : An Examination of Material Properties and Fluid Structure Interaction

This thesis examines a newly developed barrier to guide fish past turbine water intakes of hydro power plants, consisting of buoyant, “dancing” foam rods attached to the bottom of the water stream. Material properties of the wet foam is examined through density measurements and uniaxial tensile testing. Fluid structure interaction (FSI) of a foam rod in water flow is characterized experimentally, and a numerical model is developed to simulate the FSI. An average density of 566 kg/m^3 and Young’s modulus of 0.553 MPa where obtained for the wet foam. Through experimental FSI characterization, a dominating oscillation frequency of 0.89 Hz, and average amplitude of 48 mm for the rod tip where obtained. The FSI simulation captured the over all dynamics of the FSI, with a tip oscillation frequency of 0.78 Hz and an average amplitude of 53 mm for the rod tip. However, in the simulation, spanwise drifting occurred. Additionally, axial rotation was significantly larger, and bending significantly smaller compared to the experimental results. To improve accuracy of the simulation in future work, the effects of a thicker first layer in the boundary layer mesh, higher stiffening factor for the mesh deformation, and of surface roughness should be studied. To ensure accurate buoyancy in the simulation, validation of the wet foam density to might also be of interest. To examine the difference in bending, validation of Young’s modulus and experimental flow characterization might be relevant. Even so, satisfactory consistency between experimental and numerical results regarding bending might be hard to achieve, due to the heterogeneity of the foam.