Abstract
Vortex rope causes instabilities in hydro-turbines and marine turbines. It is an important issue in the utilization of ocean energy. The flow energy dissipation (FED) is one of instability problems of turbines. The FED of vortex rope can be evaluated by the entropy production rate (EPR) according to the second law of thermodynamics. The EPR will provide a visualization of the energy change and make a better understanding of the vortex rope. In this study, a swirl generator is studied by analyzing FED and vortical flow pattern with embedded Large Eddy Simulation. By comparing Liutex method with FED's sub items, it is found that the vortex rope will not produce large energy loss. The high FED is mainly produced at the vortex rope boundary where the vortex rope interacts most strongly with the surrounding fluid. Voigt line-shape function is used to quantitatively describe the vortex rope and partition the draft tube. Transition region represents the region where the interaction mainly occurred. Transition region accounts for a higher proportion than other regions. This study provides an effective way in understanding the mechanism of FED in vortex rope and can be used to eliminate vortex rope in hydro-turbines and marine turbines.
Published Version
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