This document is a technical report of a master thesis project relevant to flight performance optimization strategy. The project is titled as ”Towards flow separation control at the lip of a ducted propeller”. The project might be applicable to both ducted propeller or propeller over-the-wing configuration under high angle of attack. Flow separation occurs due to strong adverse pressure gradients caused by the viscous interaction between a moving fluid and the surface of a body immersed in the flow. The larger the separation region is, the larger the pressure drag on the body. The goal of the project is to investigate the effectiveness of a near-wall blowing jet method to reduce, or even completely prevent, the flow separation region at the lip of a ducted propeller. The blowing jet is investigated based on an active and passive air supply approach. The analysis has been performed on a rotating propeller in close proximity to a uniform cross-section wing model. The propeller-wing configuration is designed such that the closest proximity is achieved at the mid-span of the wing. This choice is made to minimize the 3D-effects of the flow such as wingtip vortices and boundary layer influence developing on the mounting parts and the wind-tunnel walls. Hence, the representation of a ducted propeller condition is approximated only at the mid-span of the wing. The propeller performance has been estimated by Blade Element Momentum theory (BEM) analysis. As the proximity of the propeller tip to the wing surface suppresses the blade tip vortices, and hence, increases the loading of the propeller towards the tip, the Prandtl tip loss correction is ignored to obtain the resulting pressure jump. Numerical simulations are then performed to estimate the separation point at different angles of attack. The computational domain approximates the intended experimental setup to validate the results. The freestream velocity has been selected to be 20 m/s, while the advance ratio of propeller is set to be 1.4. Compared were the results of the SST k−ω and Spalart-Allmaras turbulent models. Experimental validation of the results has been performed in the SLT wind-tunnel facility of the Low- Speed Laboratory of TU Delft. The effectiveness of the blowing jet has been analyzed in terms of the blowing coefficient which is a measure of the momentum of the blown air. The influence of the blowing coefficient on the flow field has been evaluated while the propeller is active and inactive at freestream velocity of 10 and 20 m/s. Total pressure probe readings and tufts flow visualization were considered for estimation the resulting velocity development under various blowing coefficients. Additionally, the flow field has been experimentally quantitatively visualized by using planar Particle Image Velocimetry (PIV) technique showing the impact on the blowing coefficient on the velocity field region upstream the propeller. The results of the project match with found literature that the low-blowing coefficient increases the separation region, rather than suppressing it. The exact mechanism description behind this is still unknown to the found literature, but it is suggested that the addition of low air momentum near the wall reduces the boundary layer’s momentum, inducing thickness growth and destabilization of the boundary layer, making it more susceptible to earlier separation. Based on the obtained data, the threshold where the blowing switches from detrimental to beneficial for flow separation is found to decrease with decreasing either the angle of attack or the freestream velocity. This is suggested to occur as the adverse pressure gradient over the lip under these conditions is weakened, reducing the momentum required from the blown jet to suppress flow separation. The passive air supply of the blowing jet was attempted to be provided by a flow channel collecting mass-flow downstream of the propeller and recirculating it back to the blowing slot. However, the designed channel showed no capability of flow separation suppression, indicating that the inflow velocity is highly disturbed by the flow development at the inlet location. Hence, no effective solution for a passive flow control could be found. Several recommendations are provided aiming for increasing the accuracy of future research. They concern both the numerical and experimental approach in this project, along with the propeller performance estimation.