The authors had analytically deduced the pressure coefficient at the trailing edge of Joukowski wing with Kutta's condition as functions of angle of attack, camber and wing thickness. It had been cleared that stagnation point and singular point are simultaneously disappeared with Kutta's condition at the trailing edge using Joukowski translation. This paper describes the pressure coefficient near the trailing edge of several Karman-Trefftz wings with Kutta's condition as functions of summit angle of trailing edge. As a result, when the trailing edge angle has less than ten degrees, it is physically meaningless that theoretical pressure coefficient increases suddenly near the trailing edge. Furthermore, the authors propose a method using a very thin plate to improve airfoil performance at the trailing edge.
Horizontal axis type sail-wing windmills were common in ancient Mediterranean region as the power source for milling and drainage. Typical shape of their wings was triangle characterized by light weight and simple structure. The lightness of the wings contributed to reduce the centrifugal force which damages the blades, and the simplified structure made their construction and repair easy. Due to these merits this type of windmill can be an ideal power source even in present developing countries from a standpoint of appropriate technology. These years, many micro-scale wind turbines are installed as independent power sources for street lights, signs, or just as monuments in urban areas. Among such trends, sail-wing windmills are revaluated in the modem society because of their safety, reduced noise and attractive appearance. One of the authors had conducted a study on a triangle type of sail-wing windmill, however, there is no systematic study on various sail-wing shapes until now. Therefore, in the present study, the authors classified the sail-wings into three types and evaluated their aerodynamic performance to find the optimal shape and configuration experimentally in wind tunnel. The results show that the inversely tapered sail-wing has the maximum power coefficient and over speed governing characteristics.
In the present study, the hub-height wind speed ratios for 16individual wind directional groups were estimated by the RIAM-COMPACT for Noma Wind Park, Kagoshima Prefecture. Next, the validity of the proposed estimation technique for the actual wind was examined. For this procedure, field observational data from one year period between April, 2004 and March, 2005 were used. Inthiscase, the mean error on the estimation accuracy was less than 10% and less than 5% for the monthly and annual average wind speeds, respectively. to the results for the annual average wind speed, the differcnce in the seleqted refbrence points (Wind Turbines #4 and #6) had little difference in the mean error on the estimation accuracy of the annual energy output. both refbrence points, the mean error was with in 10%.
The present paper reports performance measurements of a 300kW prototype wind turbine developed by Komai Tekko Inc., including new technical approach of site calibration technique. The site locates in the seaside industrial district facing Bay of Tokyo and there are many obstacles which potentially cause flow distortion. In Europe a wind turbine performance measurement is usually proceeded by an independent organization/institute, but there is no such an organization in Japan.Therefore, under cooperation among Komai Tekko Inc., Kyushu University, HIKARUWIND. LAB and AIST, the wind turbine performance measurement was conducted based on IEC standard combined with site calibration technique. Particularly, we applied two-dimensionalbinned site calibration methodology using flow correction factors which depend not only on wind direction but also on wind speed.
Turbulence is known to affect both fatigue loads and performance of wind turbines.Present study shows a procedure to measure turbulence intensity at the rotor center of downwind turbines in power production. Average and standard deviation of the nacelle wind speed were corrected by the correlation between nacelle and rotor center, which is provided by field tests. Furthermore, the standard deviation was corrected by the nacelle fore-aft vibration. Here, CFD did not show the interference from blades affect to fluctuation of nacelle wind speed. Present procedure was validated through field tests of SUBARU80/2.0 2MW downwind turbine. The result indicates that downwind turbines have potential to validate performance and fatigue strength considering turbulence intensity in power production as well as wind speed distribution.