Effect on Aerodynamic Efficiency of Cascade Fin Due to Presence of Locally Swept Planar Members at Subsonic Speed

Grid fin is the unconventional aerodynamic control and stabilizer surface used on several aerospace applications in place of a conventional single planar surface. it consists of intersecting planar surfaces arranged inside an outer frame. The best thing about grid fin is that it has better performance at a higher angle of attack (high control effectiveness) because of the reduction in flow separation. hence grid fins are a befitting candidate for control surfaces on highly maneuverable vehicles. It produces a lower hinge moment, which reduces the size of the actuator as well as the overall weight of the air vehicle. The reason behind the lower hinge is that it has a small chord length, so less displacement of the center of pressure along the chord. The only undesirable aerodynamic characteristic of the grid fin, is its high drag penalty especially at transonic speed due to flow getting choked inside the cells. The simplified configuration of the grid fin is named Cascade fin, there are only parallel lifting surfaces arranged between two sidewalls that lead to lower drag. Aerodynamic efficiency is an important parameter of any aerodynamic body. An improvement of this characteristic would lead to the reduced power consumption of air vehicles and mitigated fuel consumption. This paper includes studies carried out for improving aerodynamics efficiency (CL / CD) and reducing the drag of the existing configuration of cascade fin by virtue of introducing a locally swept alteration for the planar members of the baseline cascade fin. The study makes use of numerical investigations to decipher the aerodynamic differences at subsonic speed (40 m/s) with 0° to 45° angle of attack variation at intervals of 5°. The swept angle (Λ) is taken as 60°. Present numerical study shows that locally swept planar affected the aerodynamics efficiency with minor changes in the stall characteristics (stall angle). The percentage gain in average aerodynamic efficiency is about 12.09% as taken at all angles of attack.