Akira Sakurai

WAKE INTERFERENCE OF A ROW OF NORMAL FLAT PLATES ARRANGED SIDE BY SIDE IN A UNIFORM FLOW

The wake characteristic of groups of normal flat plates, consisting of two, three, or four plates placed side by side with slits in between, have been investigated experimentally. When the ratio of the slit width to the plate width (slit ratio) was small, the gap flows were observed to be biased either upward or downward in a stable way, leading to multiple, stable flow patterns for a single slit-ratio value. Some regularities were recognized in the gap-flow directions and the appearance of the flow patterns. The plates on the biased side showed high drag and regular vortex shedding, while those on the unbiased side showed the opposite. The origin of the biased flow has also been investigated with water-tank experiments, numerical calculations and wind-tunnel experiments. The-results showed that the origin of biasing is strongly related to the vortex shedding of each plate of a row.

Measurements of heat-transfer coefficients in the interaction regions between oblique shock waves and turbulent boundary layers with a multi-layered thin film heat transfer gauge.

A new type of thin film heat transfer gauge is applied to the measurements of heat-transfer coefficients in the interaction regions of oblique shock waves and fully developed turbulent boundary layers. It has been developed for the measurements of heat flux with high spatial resolution and fast response for wind tunnels with long flow duration. Experiments have been performed under the conditions of Mach number=4, total pressure=1.2MPa, Tw/T0=0.59-0.65, Reynolds number=1.3-1.5×107, and incident shock angles from 17.8 degrees to 22.8 degrees. Flow fields are visualized by the Schlieren technique. Both distributions of surface pressure and heat-transfer coefficient are measured throughout the interaction regions by scanning the shock generator parallel to the free stream. Owing to the high spatial resolution of the new sensor, complicated features of the aerodynamic heating in the interaction regions are revealed.

Automatic generation of UAV configuration by using Evolutionary Algorithm

This paper presents an automatic design method of UAV configurations using EA (Evolutionary Algorithm). Aerodynamic configuration as well as the design variables which include the parameters necessary for sizing are optimized. In automatic generation of configuration, the four principal components are defined and the combination of them are randomly selected. The design variables are optimized evaluating an objective function which reflects design requirements and the limits. Some examples show that the possibility to design a unique UAV which cannot be designed easily by human designers.

Hierarchical flight management and control of autonomous UAVs based on evolutionary coumputation and total energy concept

This paper presents a hierarchical flight management and control system for UAVs. The system composed of three layers, i.e. command interpreter layer, path planner layer, and auto-pilot layer. Path planner layer which plans a UAV’s path before flight and during flight is focussed in this paper, and it is done in two steps. Macroscopic path planning is done using evolutionary computation, and microscopic planning is done applying total energy concetp especially in terminal phase and emergency landing. In the former, waypoints are directly determined by evolutionary computaion featuring unified way of handling static and dynamic obstacles, and insertion and deletion of the waypoins. In the latter, microscopic path is determined based on total energy concept which is the sum of the potential and kinetic energy, and remaining fuel as energy. Some example off-line calclation results applying these concepts are also presented.