Optimal Kinematics for Energy Harvesting using Favorable Wake-Foil Interactions in Tandem Oscillating Hydrofoils

Pitching and heaving oscillating hydrofoils for energy harvesting can be arranged in tandem configurations that may lead to increased system efficiency. Finding the optimal kinematics for maximum efficiency is necessary in order to make this technology viable for widespread use. The efficiency increase in tandem arrays results from favorable wake-foil interactions between the trailing foil and the wake behind the leading foil. The energy extraction performance of a tandem array of flat plate oscillating hydrofoils is studied experimentally in a water flume at Re = 30k. The leading foil's motion was prescribed to produce a wake within specific regimes, and force and flow measurements of the trailing foil were acquired for varying kinematics. Heave amplitude and inter-foil phase have significant influence on energy extraction, with optimum heave values adapting to structural changes in the wake from the leading foil. Performance is less sensitive to the trailing foil pitch. Velocity fields around the trailing foil, measured using PIV for different parameters are also measured and will be discussed.