Assessment of Flow Characteristics at Two Locations in an Energetic Tidal Channel

Abstract

Inflow turbulence can impact a turbine’s power performance and load conditions and also affects wake recovery. At array scale, changes in flow conditions across a site impact the energy yield, performance and load conditions of turbines. Understanding the variation of flow conditions in time and space at deployment sites is therefore important to the tidal stream energy industry. Tidal flow field data of sufficient detail to allow turbulence characterisation remains relatively scarce. Traditional three or four beam Acoustic Doppler Current Profilers (ADCPs), which are commonly used for tidal flow resource characterisation, are limited by their spatial and temporal resolution and by the assumption of flow homogeneity across their beams. Higher resolution methods of measurement should therefore be implemented. This paper presents flow measurements that were conducted concurrently from two moored platforms in Strangford Narrows, an energetic tidal channel, separated by approximately 500 m. Between the two locations a rocky outcrop exists in the channel and the characteristics of the flow vary significantly. Two collocated instruments were used to measure the flow characteristics at each location: a five beam ADCP (Nortek Signature 1000) and an ADV (Nortek Vector). This paper compares both the flow characteristics at each location and the turbulence measurements using the different instrumentation types. The combination of instrumentation enables improved characterisation of the flow.