M.Sc Thesis

M.Sc StudentTreizer Alexander
SubjectGeneration of Energy by the Active Control of Flow over a
Cylindrical Pendulum
DepartmentDepartment of Mechanical Engineering
Supervisor PROF. David Greenblatt
Full Thesis textFull thesis text - English Version


A novel method of wind-energy generation was studied, where flow-control-induced oscillations were produced by means of dynamic boundary layer separation and attachment. Proof-of-concept wind tunnel experiments at subcritical Reynolds numbers were performed on a one-degree-of-freedom pivoted cylindrical body where pulsed dielectric barrier discharge (DBD) plasma actuators were used to control separation. In the first part of the study, static deflection experiments were performed to determine the maximum imposed aerodynamic loads as a function of control parameters and these were complimented with flow-field measurements using two-dimensional particle image velocimetry. Periodic forcing of the unloaded system was achieved by open-loop periodic modulation of the actuator. Large amplitude oscillations were observed when the modulation frequency was close to the system natural frequency. Estimation of the transient loads occurring during dynamic separation and attachment was performed using a system identification technique. In the second part of the study, a nonlinear load, typical of a positive displacement air pump, was attached to the system and calibrated. Using phase-locked actuation, simultaneous pressure and angular displacement measurements were performed to determine the integrated mean system power. Peak measured power coefficients were relatively small, namely 1. 2 %, but linear model estimates indicated values up to 2.1%. The differences were attributed mainly to load non-linearity, violation of the small angle approximation and natural system damping. Despite these modest results, the system is amenable to up-scaling because lateral force coefficients can be increased and the power coefficient increases with the square-root of the system dimensions.