In order to make clear the hysteresis behavior of biplane Wells turbine performance in deep stall condition, numerical investigations were made for the hysteretic characteristics in deep stall condition of biplane Wells Turbine. The numerical investigation was made by an unsteady three-dimensional Navier-Stokes numerical simulation. The calculated turbine unsteady performance show two characteristic loops. A counterclockwise hysteresis loop is observed in the unstalled condition and a clockwise hysteresis loop is observed in the deep stall condition. By dividing the torque and total pressure drop coefficient values between the one for upstream blade and the one for downstream one, it is found that the clockwise hysteresis loop can be seen only for the downstream blade.
In the past two decades, worldwide efforts have been devoted to the development of energy conversion from ocean waves. One of the most applicable devices for wave energy is the combination of an Oscillating Water Column (OWC) as a primary converter and a self-rectifying air turbine as a secondary one (Fig.1).
The Wells turbine is one of the most suitable air turbines for energy conversion from oscillating air flow. A lot of researches have been made for the Wells turbine and it has been found that the Wells turbine has hysteretic characteristics in an unsteady flow in unstalled condition (Inoue et al. (1987), Setoguchi et al. (1990) and Alcorn&Beattie (1998). These hysteretic characteristics should be clarified for the better design of the system for wave power conversion.
Dynamic stall of an airfoil is well known as an unsteady aerodynamic phenomenon which has hysteretic characteristics, and a lot of researchers have reported many kinds of aspects of dynamic stall of an airfoil (Ericsson&Reding (1987), Shida et al. (1987), Carr (1988) and Leishman (1990)).
