Comparative study on the aerodynamic performance of airfoil with boundary layer trip of various geometrical shapes

Abstract

Performance of small scale wind turbine (SSWT) and miniature aerial vehicles (MAV) is always effected with Laminar separation bubble. The problem of a laminar separation bubble on the upper surface of an E216 airfoil operated at low Reynolds number (Re=100000) is investigated numerically. Incompressible steady two-dimensional simulation is carried out with Transition γ − Reθ turbulence model on the airfoil with a boundary layer trip (BLT). The performance of two different types of trips, namely, isosceles triangular (IT) and right-angled triangular (RA) is compared with that of the airfoil with a rectangular (RT) trip. The trip locations used are, 17% of the chord for location-1 and 10% of the chord for location-2 from the leading edge of the airfoil, while the trip heights selected are 0.3 mm, 0.5 mm, 0.7 mm, and 1 mm. Results showed that the boundary layer trip significantly affected the laminar separation and improved the aerodynamic performance of the airfoil. Maximum improvement in drag by 17.41% and corresponding lift to drag ratio by 10.86% are obtained for the isosceles trip at location-2 for the angle of attack of 6°. There is no observable advantage for isosceles and right-angled triangular trips over rectangular trips. Considering the geometrical complexity in fabrication, the rectangular trip is recommended.

Experimental investigation on the unsteady surface pressure fluctuation patterns over an airfoil

“…In order to achieve a turbulent flow over the airfoil, or at least over the trailing edge, and to mimic the conditions at high Reynolds number flow that the actual wings experience, a tripping tape is utilized to force an early (forced) transition to the turbulent regime over the airfoils in experiments [36][37][38][39][40]. Despite its utilization in almost all experiments, the number of investigations addressing the effect on mean quantities is limited [41][42][43] and frequency dependent effect does not exist. The tripping is specifically crucial in aeroacoustic measurements, where the instabilities prior to transition lead to Tollmien-Schlichting (T-S) waves.…”

Laminar Separation Bubble and Flow Topology of NACA 0015 at Low Reynolds Number

“…This model is not depending on nonlocal terms and the intermittency is modified to allow better prediction of separation-induced transition [26,32,36]. Additionally, the model predicts the formation and structure of the separated bubble well [37][38][39]. Above all, the model is mostly used for external flow measurements at relatively high Reynolds number (Re ≈ 10 6 ) and finite low Reynolds number [28].…”