Nishino, TakafumiFisher Fernandez, Jaime Rodrigo2022-09-292022-09-292018-03https://dspace.lib.cranfield.ac.uk/handle/1826/18488Control of the separation and reattachment of the boundary layer has been the focus of research for a wide range of engineering applications, and it is known that a synthetic jet can be used as an active flow control device for such issues. This work presents a numerical analysis of the potential benefits of changing the inflow and outflow directions of a synthetic jet separately. The basic concept of this new flow control approach, named Bi-Directional synthetic jet (BDSJ), is to induce the Coanda effect due to the jet outflow directed downstream, and change accordingly the inflow direction for an efficient and directed suction of the boundary layer. A widely-used reference case (so-called NASA 2-D Hump) is used to validate the numerical model and to compare results. Three well known Reynolds-averaged Navier-Stokes (RANS) turbulence models are employed and they all show similar trends. Eleven different angles are tested for the inflow and outflow directions of the synthetic jet; the most effective configuration is then compared with the classical synthetic jet and Directed synthetic jet. It is shown that the best BDSJ configuration results in a shorter separation bubble length over the hump, suggesting the potential of BDSJ as a future active flow control device. This work also attempts to answer the question; "How a Bi-directional synthetic jet, influences the aerodynamic coefficients on a aerofoil". Simulations are carried out on an NACA 23012 at a Reynolds number of Re =2.19 • 10⁶, where a two-dimensional structured mesh is used to evaluate the impact of the amplitude and frequency of the Bidirectional synthetic jet on the aerofoil performance over a wide range of angles of attack. Three different jet oscillating frequencies are considered as well as three blowing ratios. The phase difference between the inflow and outflow jets, the position and the configuration of the jet exits are also evaluated. The results suggest that the amplitude of the jet is a key parameter to increase the lift coefficient and a gap between the inflow and outflow jet exits could positively influence the lift coefficient if the central location of the jets coincides with the separation point. On the other hand, the jet frequencies and the phase at which the jets operate do not seem to influence the aerofoil performance significantly. Finally, some guidelines and recommendations are provided to develop further the actual Bi-directional synthetic jet which may lead to its optimal design and manufacture.en© Cranfield University, 2015. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.Active flow controlaerodynamicsboundary layerdrag reductionlift enhancementsynthetic jetThesis