Aerodynamics performance of glider GL-1 based on computational fluid dynamics in optimum flight conditions

Glider GL-1 is designed as a national glider of Indonesia for aero sport gliding activity and fall into category of 15 meters class by FAI (world's air sport federation). In preliminary design phase, design requirements are derived from thermal updraft condition of Indonesia which lead to maximum rate of descent of 3 m/s and maximum turning radius of 150 m. GL-1 has wing area of 12 m² and wing aspect ratio of 17. Wing span of GL-1 is 14.283 m with length of fuselage is 6.795 m. Performance study in preliminary design gives two optimum flight conditions for GL-1 to glide, which is maximum range condition and maximum endurance condition. In maximum range condition, with maximum aerodynamics efficiency between 24 to 30, GL-1 has a velocity of 20 – 25 m/s with density of 1.225 kg/m3. In maximum endurance condition, GL-1 has a velocity of 17 – 20 m/s with the same density and minimum rate of descent between 0.66 – 1.1 m/s. Reynolds number is between 1 – 1.5 million. This paper present CFD simulation result for both optimum flight conditions predicted in preliminary design that carried out at velocity of 25 m/s for maximum range condition and 17.5 m/s for maximum endurance condition. By using full-glider meshing with total element of about 11 million, a maximum aerodynamics efficiency of 21 is obtained for maximum range condition with lift coefficient of 0.91. While minimum rate of descent for maximum endurance condition of 0.87 m/s is obtained.