Conceptual duct shape design for horizontal-axis hydrokinetic turbines

Abstract

In the present paper, conceptual duct shape design for kinetic energy extraction with hydrokinetic turbines is discussed. The goal is to find a single-passage axisymmetric geometry that holds stable flow with maximum kinetic energy flux at duct throat. For finding the optimum duct shape, the fluid flow was numerically simulated in a wedge shaped space with Flow-Simulation Software. In a multi-stage conceptual design, tabulated configurations were employed to study each geometrical characteristic separately. These include curvature of profile camber, trailing edge shape, profile tip shape, and duct exit cross sectional area. The revolved profile of each duct consists of a well constrained composite curve with few degrees of freedom. The Sketcher environment of SolidWorks Software provides a feasible method of rebuilding constrained curves. Duct shape optimization was performed based on successive flow simulation and approximation of optimum geometric dimension at optimum flow condition. The drag coefficients were compared with available experiments. Based on the numerical simulations with needle shaped leading edge, the duct throat velocity can be increased. Inversely, the flow blockage can reduce the kinetic energy flux at duct throat. The optimum duct shape has shown the greatest frictional drag coefficient and the minimum flow separation.