Active Flow Control Technologies for Energy and Propulsive Systems

Dear Colleagues,

The topic of this Special Issue concerns the latest developments and investigations in the fields of flow control with a focus on the Energy and Propulsive Engineering applications.

Boundary layer separation entails great energy losses and limits the performance of most flow related devices. It imposes severe limitations not only on the design but it also affects the operation and performance of the devices. Therefore, the control of boundary layer separation or at least its alleviation is warranted.

Active flow control (AFC) is a fast-growing multi-disciplinary science and technology aimed at altering a natural flow state or development path into a more desired state.

These methods are used majorly to achieve transition delay, drag reduction, lift enhancement, turbulence management, separation postponement, noise suppression, etc. The potential benefits of flow control may include improved performance, affordability, fuel consumption economy, and environmental compliance.

The synergy of flow and noise control technologies is relevant to air vehicles, for example, in wake deficit reduction, reduced distortion at the engine inlet, laminar flow control, as laminar flow has less structural vibration induced noise.

In the aerospace field, the flow control has a significant impact on the aerodynamic design as well as on the propulsion systems (such as jet engines and rockets) of future aerospace vehicles. Regarding engine components, flow control in turbomachinery is needed to increase efficiency of thrust and power generation while reducing environmental footprints. Efficient combustor designs and stable compressor flows using flow control are needed for such purposes.

In recent years, attention has been also focused on the control and suppression of combustion instabilities by actively and continuously perturbing certain combustion parameters in order to interrupt the growth and persistence of resonant oscillations.

Implementing active flow control methods permits also to improve the performance of wind turbines.

Remarkable developments in control theory have considerably expanded the selection of available tools which may be applied to regulate physical systems. These techniques show great benefits for several applications in fluid mechanics, including the delay of flow transition, and thus of turbulence.

Manufacturing processes have been developed in recent years to create the micro-electro-mechanical systems that have been used as sensors for pressures, temperatures, mass flows, speeds measurements, and sound detection, and as actuators for the diagnosis and control of turbulent shear flows.

Active flow control research is characterized by a highly multi-disciplinary approach including theoretical, computational and experimental fluid dynamics, aerodynamics, physics, chemistry and propulsion.

Although many flow control technologies have been identified and researched at the basic level for many decades few have ever reached maturity and full-scale deployment on a commercial product.

Potential topics include, but are not limited to:

• Accurate and efficient active and passive flow control devices for aeronautical applications

• Sensor-actuator integrated systems, with a possible focus on MEMS devices

• Smart structures combined with drag reduction techniques

• Laminar flow and engine integration technologies

• Synergy of active or passive flow and noise control technologies

• Flow control in propulsive systems

• Experimental characterization and reliable numerical simulation of flow field in the presence of actuators

• Innovative air vehicle shapes and configurations (including morphing configurations) that have the potential to improve laminar flow and load controls 

Prof. Antonio Ficarella
Prof. Maria Grazia De Giorgi
Guest Editors

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