Design, wind tunnel test, computational fluid dynamics (CFD) analysis, and flight test data analysis are conducted for the propeller of EAV-3, which is a solar-powered high-altitude long-endurance unmanned aerial vehicle developed by Korea Aerospace Research Institute. The blade element momentum theory, in conjunction with minimum induced loss, is used as a basic design method. Airfoil data are obtained from CFD analysis, which takes into account the low Reynolds number effect. The response surface is evaluated for design variables by using design of experiment and kriging metamodel. The optimization is based on desirability function. A wind tunnel test is conducted on the designed propeller. Numerical analyses are performed by using a commercial CFD code, and results are compared with those obtained from the design code and wind tunnel test data. Flight test data are analyzed based on several approximations and assumptions. The propeller performance is in good agreement with the numerical and measurement data in terms of tendency and behavior. The comparison of data confirms that the design method, wind tunnel test, and CFD analysis used in this study are practically useful and valid for the development of a high-altitude propeller.

Stability of a supersonic boundary layer over two-dimensional smooth humps with their heights considerably smaller than the local boundary layer thickness is studied by using parabolized stability equations (PSEs). Influence of humps on linear and non-linear evolution of first mode oblique wave in Mach 1.6 boundary layers is investigated. Overall destabilization influence of the hump is confirmed for both linear and non-linear cases. For the case of linear stability, an overall effect of the hump on destabilization is found to be similar to the case of subsonic boundary layer. However, in contrast to the subsonic case, considerable increase of growth rates realized in the fore part of the hump is found to contribute significantly to the overall destabilization in supersonic boundary layer. Oblique breakdown is investigated for the case of non-linear stability study. When compared to the case of flat plate, all the characteristic stages of the oblique breakdown are found to appear at a far more upstream position due to the hump. Results of parametric studies to examine the effect of hump height, location, etc. on stability characteristics are also given. Influence of dip instead of hump is also found to be very significant

A wind tunnel experiment was conducted to measure the flow over a suction side of a DAE51 airfoil at low Reynolds numbers using particle image velocimetry (PIV). Five chord Reynolds numbers ranging from 39,000 to 118,000 were investigated at angles of attack ranging from 0° to 10° at an interval of 1°. The locations of laminar separation, transition onset, transition end, and reattachment were identified by examining the measured averaged and RMS velocity data. The locations determined from the PIV data were in very good agreement with the features of measured surface pressure distribution. A large amplification of the RMS velocity leading to transition of a separated shear layer was observed centered at the inflection point of the averaged velocity profile, which indicates the important role of inflectional instability on the transition onset. The behaviors of those locations with respect to the Reynolds number and angle of attack were analyzed. For a fixed Reynolds number, the size of the separation bubble decreases quickly, and the bubble moves upstream as the angle of attack increases. The transition onset location moves upstream with increasing Reynolds number and angle of attack. The transition length becomes shorter as the Reynolds number increases. The lowest angle of attack at which a separation bubble is formed on the airfoil surface depends significantly on the Reynolds number. The movement of the separation point with respect to the Reynolds number indicates a different tendency depending on the presence of the separation bubble.