西尾 悠

<p>Behavior of a fluttering flag in a uniform flow is simulated by a three-dimensional incompressible SPH method under impermeable and permeable conditions. A permeable flag model is newly proposed on the basis of a spring-mass model. By comparing the oscillating motions of impermeable and permeable flags, it is found that amplitude of oscillation of the permeable flag is smaller than the impermeable flag. Besides, only the region near the free end oscillates under the permeable condition.</p>

<p>New airfoils for straight wing vertical axis wind turbine are designed using a genetic algorithm and two-dimensional vortex method aimed at improving the starting performance or the efficiency at a given rotational speed. Compared to a basic airfoil of NACA0018, these characteristics are improved in the optimized airfoils. It is also found that the change in the location of the aerodynamic center contributes to the increase of torque.</p>

<p>Three-dimensional simulation using an incompressible SPH method is carried out to investigate the scattering behavior of a liquid film flow spreading from the edge of a rotating disk. Computational domain is limited to a fan-shaped region near the edge of the disk using a periodic boundary condition in order to reduce the computational cost while keeping the spatial resolution as high as possible. The numerical results qualitatively agree with the experimental results though the number of ligaments is 1/2 to 1/3 of the experimental values. It is also found that droplets of nearly uniform diameters can be obtained by properly placing radial grooves at the edge.</p>

<p>Wind tunnel experiment is carried out to measure the unsteady torque generated by each blade of a straight-bladed vertical axis wind turbine using strain gauges. The results show that the measurement system measures correct torques when the wind turbine is not rotating. However, there is still a room for improvement when the wind turbine is rotating.</p>

Two-dimensional numerical simulation is carried out to investigate the leading edge receptivity of a at-plate boundary layer. It is shown that velocity fluctuations inside the boundary layer at an elliptic leading edge is suppressed by changing the local viscosity limited to velocity fluctuations. The amplitude of the velocity fluctuation in the boundary layer increases rapidly right after the junction between the elliptic leading edge and the at plate, which also depends on the frequency of the vortical disturbances given upstream.

Wind tunnel experiment is carried out to investigate the noise suppression effect of a small bump on the cavity bottom floor. The bump is placed 60% of the cavity length away from the upstream edge of the cavity. The results show that the noise suppression effect is large when the geometry of the obstacle is closer to a least-complicated two-dimensional rectangular cylinder.