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The RETERO project develops modern and scientific new methods with the aim of significantly reducing and, in the long term, completely replacing fish experiments for assessing the risk of turbine passages. The Institute of Hydraulic Engineering and Technical Hydromechanics at the Technische Universität (TU) Dresden was provided with an artificial surrogate fish (artificial lateral line probe) called iRon from the Centre of Biorobotics at Taltech, to measure and provide further insights of a fish´s point of view. Additionally, a 3D-hydronumerical model was done, to replicate the iRon with digital methods.
For this purpose, the probe was placed in a closed channel at ethohydraulic relevant zones in the Hubert-Engels-Laboratory of the TU Dresden. With the measured data, comparable parameters between laboratory and 3D-hydronumerical model were generated to demonstrate the pressure environment of the flow around fish-like bodies in various ways.
For numerical modelling the software OpenFOAM® with its pimpleFoam Solver was used. The general hydraulic performance of the channel is described applying an analytical approach, that was checked against hydraulic measurements. The resulting flow parameters on the system line of the channel was then used to validate the 3D-hydronumerical model. The sensor fish was then placed at the same ethohydraulic relevant positions in the numerical model.
The investigations show that measured pressures and derived variables in the flow around the body depend on flow parameters such as the Reynolds number and the angle of attack. The analysis of the laboratory test and the numerical evaluation lead to plausible results in the context of previous research. In particular, a pressure coefficient calculated in the numerical evaluation can be quantitatively compared with value ranges of former publications.
In addition, a spatial visualization of the derived pressure parameters of the laboratory and 3D-numerical models is created, that illustrates the hydraulic phenomena of water flowing around fish. The so called extrapolated pressure coefficient, which combines laboratory and numerical values, is introduced as a comparative quantity. This work provides mathematical-numerical approaches for force calculation across the profile surface of a streamlined body and presents the pressure state of the surrounding flow area in a new visual form. Ultimately, the methodology will provide in future iterations a way to quantify the swimming capacity of fish in real time.