Aerodynamic characteristics and laminar bubble separation study on a generic light aircraft model

Abstract

This paper presents the aerodynamic characteristics, flow separation and laminar bubble analysis of a generic UTM-LST light aircraft model at low Reynolds number. The complex interaction between flow separation and laminar bubble is unclear to date. The model has overall length of 1.3m and wingspan of 1.5m and has been designed for wind tunnel experiments in Universiti Teknologi Malaysia Low Speed Wind Tunnel, Aerolab. The aircraft model is equipped with several control surfaces such as ailerons, rudder, elevators and flaps. The experiments were conducted at the speed of 35 m/s corresponding to Reynolds number of 0.515 x 106 and at angles of attack ranging from 0° to 16°. The experiments were performed at several pitching and yawing configurations. In order to investigate the effects of control surfaces, several control surfaces were changed during the experiments; for this paper, however, only elevator changes will be highlighted. Three measurement techniques were employed during the experiments; the first one was the Steady balance, the second was the surface pressure while the last one was the tuft flow experiment. The main observation from steady balance data was that the aircraft possesses longitudinal static stability for all test cases. The main observation from the surface pressure measurement and tuft experiments is that the laminar bubble separation occurred at lower angles of attack of the wing. This separation is seen to be travelling towards the leading edge as the angle of attack is increased and eventually results in flow separation.