Computational Tool for a Mini-Windmill Study with SOFT

In this paper, we present a parallel computational framework for the completely automated design of a Vertical Axis Fluid Turbine (VAFT). Simulation, Optimum design, Fabrication and Testing (SOFT) of the VAFT is integrated into a hardware/software environment that can fit into a small office space. The components of the four steps design loop are as follows Simulation: We use a parallel CFD algorithm to run a direct simulation of the fluid structure interaction problem. We derive from that computation the torque and the average rotation speed for a given friction coefficient on the rotor shaft and an average flow speed. Our objective is to get the most power out of the windmill, consequently the highest rotation speed possible. Optimization: We optimize the shape of the blade section with a genetic algorithm and/or a surface response. The evaluation of the objective function (average rotation speed) corresponds to the direct simulation of the Navier Stokes flow interacting with the rotating turbine, until reaching a stationary regime. Because this simulation is compute-intensive, we distribute the evaluation of the objective function for the different shapes (gene or parameter combinations) on a network of computers using an embarrassingly parallel algorithm. Fabrication: The optimization procedure results in a supposedly optimum shape in the chosen design space. This shape is sent to a 3-D printer that fabricates the real turbine. This turbine is set up such that it can be easily mounted on a standard base equipped with an electric alternator/generator. Testing: The windmill is tested in a mini wind tunnel. The electric output is measured and a video camera can directly monitor the windmill rotation through the transparent wall of the wind tunnel. This information can be analyzed by the computer system and comparison with the simulation is assessed. Figure 1 gives a graphical overview of the SOFT concept.

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