Numerical Simulation of Water Flow through a Nano-Hydraulic Turbine of Waterfall-Type by Particle Method

This study simulates the flow through an impulse-type small-scale hydraulic turbine utilizing a waterfall of extra-low head. The two-dimensional Moving Particle Semi-implicit (MPS) method is employed for the simulation. The fluid is discretized by particles, and the flow is computed by the Lagrangian calculation for the particle motion. When the distance between the particles discretizing the waterfall of a width , , is set at , the flow can be simulated with the sufficiently high spatial resolution, and the rotor performance can also be favorably predicted. The present simulation also successfully analyzes the effect of the rotational speed of rotor on the flow and the turbine performance. 1. Introduction Hydropower is one of the promising renewable energy resources. It is converted to electric energy through hydraulic turbines. In Japan in 2010, approximately 10% of all supplying electric energy is provided by hydraulic power generations. The percentage is expected to increase steadily on the basis of a government policy promoting the development of renewable energy. As large-scale hydroelectric plants require huge dams and long conduits, the places for the construction are hardly remained. Thus, expectations for the development of a small-scale hydropower, of which output is less than 1000？kW, have been increasing. When natural disaster occurs, the large-scale centralized hydraulic power plants may lose the power supplying ability due to the collapse of the power grid. Since the small-scale hydropower, existing in small-scale rivers, irrigation canals, and industrial drainages, distributes widely in Japan, it realizes the small-scale distributed power generation. The small-scale hydropower can contribute the local production for local consumption of electric power, which is more resistant to disaster. Consequently, the development is also of great worth from the viewpoint of constructing a disaster-resistant society. To exploit effectively the small-scale hydropower, various types of hydraulic turbine have been presented [1–5]. Ikeda et al. [6] developed an impulse-type hydraulic turbine utilizing waterfalls of extra-low head which is 2？m or less in small rivers and agricultural canals and so forth. The nano-hydraulic turbine, of which output power is less than several kW, can be easily carried to the places where they are necessary, and produces electric power easily without damaging the environment. Ikeda et al. [6] investigated the power characteristic of the turbine through a laboratory experiment and made clear the flow inside the rotor by the