Numerical investigation of dynamic characteristics of BBDB in the time domain using the REEF3D CFD model

Abstract

This study employs the REEF3D numerical model to simulate and validate the motion behavior of the Backward Bent Duct Buoy (BBDB) in two and three dimensions, providing a reliable tool for advancing BBDB research and development. A time-domain approach is applied to analyze the interactions among fluid, the BBDB structure, mooring lines, and airflow during a single motion cycle. The study compares energy extraction between 2D and 3D configurations and evaluates energy conversion efficiency under short-period and long-period wave conditions. The results show that the floating OWC-type BBDB converts energy by expelling air during wave crests and drawing in air during wave troughs, with air expulsion lasting approximately 50 % longer than intake. The energy extraction efficiency in 3D is 1 %-22 % higher than in 2D, primarily due to higher fluid velocity within the BBDB dent and greater pressure differences in the air chamber under 3D conditions, both of which are critical for enhancing energy conversion.