Flow control is a technical means of manipulating the behaviors and characteristics of fluid flows. The ultimate goal is to enhance or modify flow properties, such as velocity, pressure, and turbulence intensity, in order to achieve specific engineering objectives. Flow control can be broadly classified into two categories: passive and active. Passive flow control is generally simpler and more cost-effective than active control, but it may have limited effectiveness and may not be suitable for all types of flows. Active flow control, while more complex and often more expensive, can achieve higher levels of flow manipulation and may be applied to a wider range of flows.

The science behind Flow control is multidisciplinary and refers to aspects of fluid mechanics, materials science, control theory, and numerical modeling. The techniques of flow control have important applications in various fields, including aerospace, automotive, civil, and biomedical engineering, and can help to improve efficiency, to reduce energy consumption, to increase performance, and to improve safety and reliability.

This Special Issue from new open-access journal Aerospace Research Communications showcases recent advances and challenges in the fundamental understanding and practical implementation of flow control techniques.

Topics of interest for this Special Issue included but were not limited to:

- Active and passive flow control techniques, including micro-riblets, coatings, plasma actuation, synthetic jets, and vortex generators;
- Control of turbulence and transition to turbulence, including laminar-to-turbulent transition control, drag reduction, and mixing enhancement;
- Flow control in complex geometries and unsteady flows, including boundary layer separation control, flow-induced vibration suppression, and flow oscillations control;
- Flow control under extreme conditions, such as hypersonic flights, space or Martian environments;
- Flow control for drag reduction and energy savings, including aerodynamic drag reduction, hydrodynamic drag reduction, and thermal management;
- Flow control in biomedical and environmental applications, including drug delivery systems, blood flow control, and pollutant dispersion control; and so on.

Theoretical, numerical, and experimental studies were all welcome, as were reviews and case studies that presented successful flow control implementations. The articles should provide new insights into flow control phenomena, contribute significantly to the development of effective flow control strategies, and demonstrate their potential impact on engineering applications. Additionally, submissions highlighted interdisciplinary research work by combining flow control with other fields, such as machine learning, control theory, and materials science.

Special Issue cover photo taken from SSECOID project: "Stability and Sensitivity Methods for Flow Control and Industrial Design", Grant agreement No 955923. MARIE SKŁODOWSKA-CURIE ACTIONS Innovative Training Networks (ITN).

Keywords: Flow control, Drag reduction, Flow separation, Energy saving, Open access