Unsteady effects in flows past stationary airfoils with Gurney flaps due to unsteady flow separations at low Reynolds numbers
Journal Title: INCAS BULLETIN - Year 2015, Vol 7, Issue 4
Abstract
This paper presents the analysis of the unsteady flows past stationary airfoils equipped with Gurney flaps at low Reynolds numbers, aiming to study the unsteady behavior of the aerodynamic coefficients due to the flow separations occurring at these Reynolds numbers. The Gurney flaps are simple but very efficient lift-increasing devices, which due to their mechanical simplicity are of particular interest for the small size micro-air-vehicles (MAV) flying at low speed and very low Reynolds number. The unsteady aerodynamic analysis is performed with an efficient time-accurate numerical method developed for the solution of the Navier-Stokes equations at low Reynolds numbers, which is second-order-accurate in time and space. The paper presents solutions for the unsteady aerodynamic coefficients of lift and drag and for the lift-to-drag ratio of several symmetric and cambered airfoils with Gurney flaps. It was found that although the airfoil is considered stationary, starting from a relatively small incidence (about 8 degrees) the flow becomes unsteady due to the unsteadiness of the flow separations occurring at low Reynolds numbers, and the aerodynamic coefficients display periodic oscillations in time. A detailed study is presented in the paper on the influence of various geometric and flow parameters, such as the Gurney flap height, Reynolds number, airfoil relative thickness and relative camber, on the aerodynamic coefficients of lift, drag and lift-to-drag ratio. The flow separation is also studied with the aid of flow visualizations illustrating the changes in the flow pattern at various moments in time.
Authors and Affiliations
Dan MATEESCU
BOOK REVIEWS: Quantitative Methods (Second Part) Probability Calculation, Issues of Numerical Computation, Linear Programming, The Method of the Critical Path, Financial Mathematics Metode cantitative (Volumul II) Calculul probabilitatilor, Elemente de calcul numeric, Programare lineara, Metoda drumului critic, Matematici financiare Sorin BERBENTE, Corneliu BERBENTE Editura BREN, Seria “Busi
Dynamic study of the virtual prototype of the IAR-99 SOIM Aircraft
This paper contains a dynamic study of the IAR-99 SOIM aircraft using ADAMS, multibody dynamic solutions. First, the analysis of the whole airplane is envisaged and then the analysis of the flight control system and the...
SIMULAND - A CODE TO ANALYZE DYNAMIC EFFECTS DURING LANDING
The landing gear of an aircraft is part of the aircraft structure. It is the most critical part of the flight mission and also the component that will likely cause the most problems in the aircraft design. The landing ge...
Some Aspects Regarding “Sense and Avoid” Requirements for UAV Integration in the National Air Space
The purpose of this article is to show the importance of mission planning in a fully automatic flight and the critical role of implementing Sense & Avoid (S&A) procedures at different categories of UAVs. Modern o...
Numerical Methods for Transverse Vibration Analysis of Straight Euler and Timoshenko Beams
This paper presents a short review of numerical methods used for lateral vibration analysis in the case of straight Euler and Timoshenko beams. A particular integral method is described with more details. This approximat...