CONTROL OF FLOW SEPARATION OVER NACA 0015 AIRFOIL USING SYNTHETIC JET ACTUATORS

Mechanical

Abstract

In this paper the concept of active flow control using an array of synthetic jet actuators has been investigated. Synthetic jets are the one type of actuators that will be used in this research to introduce important modification to the pressure distribution levels that appear over the lifting surface of airfoil model when the flow separation exists. Two synthetic jet actuators arrays were used; the first one placed at 3% c and the second array located at 6% c on the upper surface of a NACA0015 airfoil. The experiments are conducted at Re=455000 in 8 different angles of attack 0º to 15º using the wind tunnel at University of Diyala. The first part of this paper concentrates on making comparison of the collected experimental data of the pressure distribution over NACA0015 airfoil at Re = 4.4x105 at angle of attack varied from 0.0 to 20 degrees without synthetic jet actuators (baseline case study) and previous experimental results as a baseline validation of the onset of flow separation location. Figure 3 and 4 clearly showed that the pressure distribution and the calculated lift were converged in the stall region at high angle of attack.
In the second part of this study we had utilized a NACA0015 airfoil of 300 mm chord length with a rounded leading edge of 20 mm diameter. 18 discrete synthetic jet actuators with 1.2 mm diameter is distributed along the lifting surface of the wing. This distribution is used to investigate the effect of jets and vertical structures on the characteristics of pressure coefficients (Cp) and flow separation over the airfoil. Pressure and lift coefficients have been measured and calculated by using surface pressure measurements technique that uses 29 pressure tapings over the lifting surface of the wing. A piezo-ceramic diaphragms technology of 15mm diameter have been used in the experiments and excited at a variety of frequencies (resonant frequency and vortex shedding separated flow frequency) in order to get the effective interaction between the synthetic jets and separated boundary layer which is the most significant parameter of producing the vertical structure that affects the flow separation. The results showed that at 3% c SJA location, the best enhancement in the lift was seen at Vp-p of 8 which increased by about 0.1. However, the overall results showed that maximum enhancement in lift of about 0.2 at 6% c.