In-situ orifice calibration for reversing oscillating flow and improved performance prediction for oscillating water column model test experiments

Abstract

Performance characterization of oscillating water column (OWC) wave energy converters (WEC) is commonly assessed by conducting physical scale model experiments of OWC models fitted with orifice plates to the air chamber to both; simulate the power take off (PTO), and measure the air flow rate. Generally it is assumed that a single calibration factor can be used for bi-directional air flow measurement, however this paper shows the assumption can be in-accurate and that it is necessary to have separate inflow and outflow calibration factors. This paper presents (i) a novel method for in-situ calibration of an orifice and (ii) a simple algorithm to reduce noise during air flow reversal (low air chamber pressure differential). Application of this technique results in more accurate flow rate prediction and consequently, better prediction of the power absorbed by the power take-off for OWCs.