An Equivalent Circuit Model for the Reconfigurable Ducted Turbine Array Concept

Abstract The reconfigurable ducted turbine array concept is an energy harvesting method proposed to reduce the so-called levelized cost of energy extracted from naturally occurring flows (e.g., from wind and water currents.) Duct augmentation is proposed to achieve higher power coefficient than the Betz limit for open turbines, among other (e.g., structural) reasons. Ducted or shrouded hydrokinetic turbines with a contracted throat area can be used to eliminate blade tip vortex, and to potentially increase the flow velocity at the rotor cross-section, consequently speeding up the rotor to improve electro-magnetic efficiency. In a recent paper by the authors, an equivalent circuit model for a single duct was proposed to understand the effects of geometric design variables of the duct. These variables are contraction ratio, aspect ratio, hub-to-throat ratio, etc. The parameterized circuit model was used to study the flow behavior of the ducted geometry in terms of equivalent resistances. The current paper presents an extended equivalent circuit model by adding the effects of turbulence, gravity, and hydrostatic pressure. The unknown parameters of the equivalent circuit model are identified using three-dimensional computational fluid dynamics simulations, and by curve fitting using the least squares method. The circuit model is then used to identify design variables that result in desirable flow behavior from duct augmentation.