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This study experimentally investigates aerodynamic characteristics and flow fields of a smooth owl-like airfoil without serrations and velvet structures. This biologically inspired airfoil design is intended to serve as the main-wing for low-Reynolds-number aircrafts such as micro air vehicles. Reynolds number dependency on aerodynamics is also evaluated at low Reynolds numbers. The results of the study show that the owl-like airfoil has high lift performance with a nonlinear lift increase due to the presence of a separation bubble on the suction side. A distinctive flow feature of the owl airfoil is a separation bubble on the pressure side at low angles of attack. The separation bubble switches location from the pressure side to the suction side as the angle of attack increases and is continuously present on the surface within a wide range of angles of attack. The Reynolds number dependency on the lift curves is insignificant, although differences in the drag curves are especially pronounced at high angles of attack. Eventually, we obtain the geometric feature of the owl-like airfoil to increase aerodynamic performance at low Reynolds numbers.

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Marine resource survey by an underwater vehicle is expected. To realize cheap self-positioning for the underwater vehicle, we have been developing on the acoustic positioning system which is low cost and easy to maintain. The acoustic positioning system has four hydrophones which consists of molding commercially available MEMS micro phones with pressure-resistant resin, an audio device, and a micro controller. To evaluate the system, positioning experiments was performed in the small tank. In the experiments, the system detected delay time among four hydrophones, however its positioning was not good accuracy. In the future, we will improve the accuracy of positioning by interpolating data and considering the effect of baseline.