Universitat Politècnica de Catalunya, Spain
Ing. Xavier Guerrero has obtained at the age of 21 his Bachelor degree in Aeronautical Engineering at ETSEIAT-UPC. Dr. Ing. JM Bergadà. Mechanical Engineer (1990), PhD in Mechanical Engineering (1996). From 1990 to 2010 his research field was Fluid Power, having spent over 10 years 2000-2010, collaborating with the Mechanical Engineering department at Cardiff University UK. During the last 5 years 2010-2015, his research focuses on theoretical and computational Fluid Mechanics. He has over 25 years of experience at UPC Fluid Mechanics Department. Dr. David del Campo Aerospace Engineer. PhD in Fluid Mechanics. Lecturer at the School of Mechanical and Aerospace Engineering of the Technical University of Catalonia (Terrassa, Spain). His main research area is Computational Fluid Dynamics applied to flow control devices. Dr. Vanessa Del Campo has been working for the Aerospace Department at the UPC (Barcelona) for more than six years. PhD on experimental Aerodynamics and Wind Turbines, carried out at Rutgers University (USA) and TUDelft (Holland). She is actually investigating flow control devices within the Research Group L’Aire. She studied Aerospace Engineering at the UPM (Madrid) and RWTH (Aachen).
This paper presents the effects of using a Zero Net Mass Flux actuator (ZNMF) on a baseline 21-percent thick NACA 4421 airfoil for stall delay. The first part of the study presents the comparison of the CFD simulations with the available experimental data of the airfoil without considering the actuation of ZNMF. A very good agreement of the CFD simulations was obtained for the lift curve, therefore validating the CFD model used. The original lift curve presented a stall around 13º angle of attack, this is why a range of angles of attack (α) near this value were studied at 7º ≤𝛼 ≤ 14º. In the second part of the study, the ZNMF was set up in the airfoil. The slot position was located at 17% of the chord, while its length was established in 2 mm. The ZNMF performance was studied at three different frequencies (𝑓=45 𝐻𝑧,250 𝐻𝑧,500 𝐻𝑧), the lower one corresponds to the shedding frequency when the angle of attack was 7º. During the study the following parameters were kept constant, Reynolds number based on the chord length was 𝑅𝑒=3•106, velocity ratio was 𝑉𝑚𝑒𝑎𝑛𝑈∞=0.701, and momentum coefficient based on the half period mean velocity, was 𝑐𝜇=0.03%. The results show a separation point downstream displacement of 4% versus the original position, whenever the frequency was 45 Hz, the rest of the frequencies studied produced an upstream displacement of the separation point. In addition, when studying the lift coefficient under dynamic conditions, it was observed that the oscillation amplitude suffered a small decrease when the ZNMF actuation frequency was 45 Hz.