Application of Entropy Production Theory for Evaluating the Performance of a Gorlov Hydrokinetic Turbine

Abstract

The main objective of this investigation is to evaluate the relationship between the Entropy Generation Rate (EGR) and the performance of a Gorlov Hydrokinetic Turbine (GHT). Experimental and numerical research is conducted on a fully submerged GHT in an open channel. The numerical results of the power coefficient are validated using experimental data. ANSYS CFX 23.1 is applied for CFD simulation of the two-phase, transient and turbulent flow around the GHT in the open channel. \(k - \omega\) SST and the homogeneous multiphase model are the tools that are utilized for modeling turbulence and the two-phase flow. The numerical results are used for calculating the turbulent, direct and total EGR in the open channel and also the rotating domain around the rotor. The results show that the 95% of the total entropy is produced by the turbulence. Comparing the variations of \(C_{P}\) and the integral of the total EGR at one rotation of the turbine showed that the minimum (or maximum) generated entropy is not in correspondence with the maximum (or minimum) power coefficient. This phenomenon is due to the fact that the maximum \(\frac{Lift}{{Drag}}\) (or the \(C_{P\max }\)) occurs at a bigger attack angle in comparison to the minimum drag force at which the total EGR is minimum. Evaluating EGR contours on a plane crossing the mid-section of the rotor and on the surfaces of the blades showed that the leading edge, the separated boundary layer region, and the wake zone near the trailing edge are the main sources of entropy generation in the rotating domain.