# Flow Control, Active and Passive Applications
## 2 Book Contents  
The articles presented in this book are related to novel flow control technologies and are divided into four main categories. The first one presents several **Passive Flow Control** (PFC) applications, which highlights the current relevance of passive methodologies. PFC is used to improve the performance of axial compressors by reducing the generation of shedding vortices at the trailing edge of a blade. This was initially investigated by [PERSON] et al. [1]. Flow field improvements in highly loaded compressors and aeroengines are studied numerically by [PERSON] et al. [2] and [PERSON] et al. [3], respectively. In both cases, it was observed that appropriate three-dimensional blading resulted in an increase in static pressure and a reduction in the influence of secondary flows. A flapping bionic wavy leading edge wing is studied by [PERSON] et al. [4], and they realized that it generated a higher lift than conventional airfoils. The passive flow-control application section is closed by the transient analysis undertaken on cruise missiles' submerged inlet by [PERSON] and [PERSON] [5]. The use of a distributed submerged inlet proved to have clear advantages compared to the conventional inlet. Closely related to passive flow control applications is the section related to **surface micro-machining**, where micro-texturing is employed by [PERSON] et al. [6], to reduce the drag and modify the cavity area in hydrostatic bearings. Micro-groves are used by [PERSON] et al. [7], to reduce the drag in an Unmanned Aerial Vehicle's (UAV's) fixed wing. The next section presents several **Active Flow Control** (AFC) investigations. In theresearch by [PERSON] et al. [8], the effectiveness of a pulsating jet is compared with a steady blowing jet, aiming to control the flow on a turbine airfoil trailing edge. Several injection frequencies were evaluated, and they demonstrated that pulsating forcing is more effective than steady actuation. A parametric optimization considering three AFC parameters on an NACA-8412 airfoil at an Angle of Attack (AoA) pf 15 degrees and Reynolds number of 68.5\({}^{\circ}\)10\({}^{3}\) is undertaken by [PERSON] and [PERSON] [9]. The effectiveness of using plasma actuators on an NACA 0015 airfoil at pre-stall AoA at a Reynolds number of 63000 is analyzed by [PERSON] et al. [10]. An optimized design of a slat channel configuration, aiming to increase the lift of a given airfoil profile, is presented by [PERSON] and [PERSON] [11]. In fact, this final paper opens the door to the final chapter, which is **Optimization Techniques** (OT). At present, in many applications and especially those involving AFC technology, it is necessary to optimize the parameters to minimize the energy used for the application while maximizing the outcome. In AFC applications, five parameters need to be optimized, and despite the fact that parametric optimizations can be quite useful, the use of optimizers based on Genetic Algorithms (GA) or gradient-based methods appear to be a much more precise way to accurately tune the required parameters. This is the direction of the work conducted by [PERSON] et al. [12]. In this research, the performance of GA and gradient-based methods is compared when these methods applied to an SD7003 airfoil to tune the AFC parameters. A hybrid evolutionary optimization method (HCGA) in combination with a CFD solver, is presented in the work of [PERSON] et al. [13], as a decision-maker design tool for aerodynamic shape design. The final contribution of this book was made by [PERSON] and [PERSON] [14], who present a review of the different flow control techniques used for gust load alleviation.