In a turbomachine rotor, the gap between the rotor tip and the stationary casing creates tip-leakage vortices. These vortices act like a blockage to the incoming passage flow and effectively reduce the pressure ratio across the rotor stage, cause unsteadiness and vibration of the rotor tip, and lead to aerothermal losses due to complex secondary flows. Hence, mitigating the strength of these vortices is important for increasing the efficiency of a turbomachine. In this work, a simple actuation strategy was investigated with steady actuation of dielectric-barrier-discharge (DBD) plasma actuators. Investigation primarily involves the straight actuation which was operated in a steady as well as a minor comparison to a segmented actuator scheme to show the benefit of the straight actuation. The tip-leakage vortices were formed in the tip-gap of a single NACA-65 airfoil of chord 10 cm mounted in a suction-type wind tunnel with static tip-gap height between the airfoil and the floor. In the tip gap of the test section of the airfoil, DBD actuators were placed along the chord of the airfoil in the tip-gap. The major objective of this research was to investigate the effectiveness of steady forcing on the tip-leakage vortex. Stereo-particle image-velocimetry (SPIV) was used to measure the flow field around the tip gap under the base line and the forcing case. A numerical study was conducted by using RANS computations with a transition model for different forcing configurations. Results from this simulation indicated that when the tip gap was 2% of the chord and free stream velocity of 2.7 m/s, the strength of the tip leakage vortex was significantly attenuated for a blowing ratio of approximately 1. This attenuation was the result of a reverse flow in the tip gap where a standing vortex was found to form in the simulation. Comparing the base line with the steady forcing cases demonstrates the success the DBD actuators to mitigate the TLV.
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Master of Science in Mechanical Engineering (M.S.M.E.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Mechanical Engineering; Thermo-Fluids Track
Length of Campus-only Access
Masters Thesis (Campus-only Access)
Anzalotta, Christian, "Active Control of Tip Leakage Vortex using DBD Plasma Actuators" (2021). Electronic Theses and Dissertations, 2020-. 641.