Field measurement and numerical study of tidal current turbulence intensity in the Kobe Strait of the Goto Islands, Nagasaki Prefecture

Abstract

The present paper is focused on evaluating the turbulence conditions in a marine nature channel, since this is one of the key factors when designing tidal energy converters. The location selected for this study is the Kobe Strait, a narrow channel between Wakamatsu and Nakadori Islands in Goto Archipelago (Nagasaki Prefecture). The field measuring campaign was carried out from February 27to March 14, 2015, using an Acoustic Doppler Current Profiler working with an 8 Hz sampling rate. Turbulence conditions for different depth layers in the measuring point are evaluated and defined in terms of turbulence intensity, integral time scale and integral length scale. The Kobe Strait hydrodynamics were simulated by an FVCOM numerical model, which was validated with velocity and water elevation measured data. This model was used to evaluate the relative vorticity reality over the area of the study. Finally, due to the large-scale dimension of turbulence in the measuring point, a new formula relating turbulence intensity and vorticity is proposed and utilized to estimate the turbulence intensity conditions in the Kobe Strait.