Experimental reconstruction of the local flow field in a Wells turbine using a three-dimensional pressure probe

Abstract

Among the various solutions suggested for wave energy harvesting, the ones based on the oscillating water column (OWC) principle are considered as the most promising, due to their constructive simplicity and reliability. These systems convert sea wave energy into pneumatic energy in the form of a bi-directional airflow that can conveniently turned into mechanical energy by a Wells turbine. Since their introduction, Wells turbines have been studied extensively in order to characterize their performance. Most of the experimental studies have focused on global machine performance analyses, while the studies focusing on local performance analyses are limited. This work presents a detailed experimental investigation of a small-scale Wells turbine coupled to an OWC simulator. The turbine aerodynamic characteristic has been identified with global measurements, while a miniaturized aerodynamic probe has been used to evaluate local performance, by reconstructing the three-dimensional flow field upstream and downstream of the turbine during a complete regular wave period. Local analyses aid to explain global turbine performance, highlighting the main differences between inflow and outflow phases. Moreover, they allow to describe the variation in loading along the blade radius, and to evaluate the blade design law, which justifies the limited Wells turbine aerodynamic performance.