Comparison of dense optical flow and PIV techniques for mapping surface current flow in tidal stream energy sites

Abstract

Marine renewable energy site and resource characterisation, in particular tidal stream energy, require detailed flow measurements which often rely on high-cost in situ instrumentation which is limited in spatial extent. We hypothesise uncrewed aerial vehicles (UAV) offer a low-cost and low-risk data collection method for tidal stream environments, as recently techniques have been developed to derive flow from optical videography. This may benefit tidal and floating renewable energy developments, providing additional insight into flow conditions and complement traditional instrumentation. Benefits to existing data collection methods include capturing flow over a large spatial extent synchronously, which could be used to analyse flow around structures or for site characterisation; however, uncertainty and method application to tidal energy sites is unclear. Here, two algorithms are tested: large-scale particle image velocimetry using PIVlab and dense optical flow. The methods are applied on video data collected at two tidal stream energy sites (Pentland Firth, Scotland, and Ramsey Sound, Wales) for a range of flow and environmental conditions. Although average validation measures were similar (~ 20–30% error), we recommend PIVlab processed velocity data at tidal energy sites because we find bias (underprediction) in optical flow for higher velocities (> 1 m/s).

PIV-MyoMonitor: an accessible particle image velocimetry-based software tool for advanced contractility assessment of cardiac organoids

“…Therefore, the accuracy of analysis may be compromised in situations involving abrupt changes in the shape of objects and the pixel intensity comprising the object. Additionally, it can struggle to accurately track the movement of objects in videos when they overlap and are hard to be distinguished from the background ( McIlvenny et al, 2023 ). Consequently, applying optical-flow-based method may pose challenges in analyzing 3D tissue models due to the deformation of cell shapes during contraction and the overlapping of cells.…”

Comparison of Schlieren-based techniques for measurements of a turbulent and wavy free surface

“…Their chosen algorithm is the Horn & Schunk (Horn & Schunck, 1981b). To our knowledge, the comparison of the Farneback algorithm to crosscorrelation has been performed just once (McIlvenny et al, 2022). We therefore compare the displacement field output between the Farneback algorithm and cross-correlation.…”

River Surface Velocimetry Based on Virtual River Dataset and Modulated-RAFT

“…Besides, we also introduced two extra optical flow model for comparison. The first one is Horn-Schunck (HS) [28], which is a traditional mechanism based method and widely used in RSV estimation recently [29]- [31]. The second one refers to the method proposed in [17], which is called as ARAFT in this paper and works similarly like our method.…”