Fish swimming kinematics in the wake of a vertical axis turbine

The swimming kinematics of juvenile rainbow trout (Oncorhynchus mykiss) were experimentally evaluated in the flow field around a three-bladed vertical axis turbine (VAT). Fish were tested under two discharge conditions, with stationary VAT or rotating at optimum tip speed ratio. PIV measurements were used to measure the hydrodynamics, and the fish kinematics including centre of mass, head and tail position and orientation, and swimming speed were studied using an open-source motion tracking algorithm.

The flow field was characterized by flow acceleration on either side of the turbine, shear layers interfacing the free stream flow and the wake, and a low momentum region that was asymmetric relative to the rotor’s centerline. Fish reaction to the flow changes induced by the turbine blockage and rotation did not significantly vary among the test cases, where fish swam in the vicinity of the turbine, navigated the flow past the turbine from wake to upstream of the turbine, but remained predominantly in the low momentum wake for increased energy conservation. Future work will relate the fish motion to the local flow properties upstream and in the turbine wake.