Computational Study of the Interaction Between Hydrodynamics and Rigid Body Dynamics of a Darrieus Type H Turbine

Abstract

The present study discusses two-dimensional numerical simulations of a cross-flow vertical-axis marine (Water) turbine (straight-bladed Darrieus type) with particular emphasis on the turbine unsteady behavior. Numerical investigations of a model turbine were undertaken using commercial computational solvers. The domain and mesh were generated using a glyph script in POINTWISE-GRIDGEN, while the simulations were performed in ANSYS-FLUENT v14. For the simulation, a sliding mesh technique was used in order to model the rotation of the turbine; a shear stress transport k–ω turbulence model was used to model the turbulent flow. In order to simulate the interaction between the dynamics of the flow and the Rigid Body Dynamics (RBD) of the turbine a User Define Function (UDF) was generated. The primary turbine operational variables of interest were the evolution of torque, power, and runaway speed. Numerical results show that as the freestream velocity is increased, the runaway angular speed of the turbine increases, which is consistent with the observation that the frequency of oscillation of the angular velocity (in the quasi steady-state) increases as the freestream velocity also increases. For a given turbine, it was observed that the increment in the moment of inertia of the turbine does not influence the average value of the runaway angular velocity (quasi-steady state) but causes an increase in the time taken for achieving this quasi steady-state.