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Actuators
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Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition
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Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition

A special issue of Actuators (ISSN 2076-0825). This special issue belongs to the section "Control Systems".

Deadline for manuscript submissions: 30 June 2026 | Viewed by 8285

Special Issue Editors

Prof. Dr. Hui Tang

E-Mail Website
Guest Editor
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
Interests: flow control; fluid-structure interaction; AI for fluid dynamics
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Xin Wen

E-Mail Website
Guest Editor
School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Interests: active flow control; data mining and data fusion in fluid mechanics
Special Issues, Collections and Topics in MDPI journals
Dr. Feng Ren

E-Mail Website
Guest Editor
School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China
Interests: active flow control; flow-structure interaction; flow-induced acoustics; computational flow dynamics
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Active flow control (AFC) utilizes local active perturbations to induce global flow field changes that result in a net improvement in performance. For decades, it has been a vibrant research area with potential applications in a wide variety of problems of academic and industrial interest. Recent developments in actuation technologies and computational/experimental methods, along with the re-booming of machine learning techniques, have made it possible for AFC to be more efficient, robust, and intelligent. In 2021 and 2023, we proposed two Special Issues to showcase and discuss new advances in AFC. Eleven and twelve excellent papers were collected respectively that pushed the boundaries of this research area, both in fundamentals and in applications. Following its success, we would like to continue the efforts here by calling for the third edition of this Special Issue. The topics of interest include, but are not limited to, the following:

  • Design and development of novel actuators for AFC;
  • Theoretical/computational/experimental studies on AFC;
  • New control strategies in AFC;
  • Machine-learning-guided AFC;
  • New AFC applications.

Prof. Dr. Hui Tang
Prof. Dr. Xin Wen
Dr. Feng Ren
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Actuators is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • active flow control
  • sensors and actuators
  • control of flow instability
  • flow separation control
  • mixing control
  • turbulence control
  • flow-induced vibration control
  • aeroacoustics control

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Related Special Issues

Published Papers (6 papers)

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Research

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20 pages, 3437 KB  
Article
Deep Reinforcement Learning-Guided Bio-Inspired Active Flow Control of a Flapping-Wing Drone for Real-Time Disturbance Suppression
by Saddam Hussain, Mohammed Messaoudi, Nouman Abbasi and Dajun Xu
Actuators 2026, 15(5), 231; https://doi.org/10.3390/act15050231 - 22 Apr 2026
Viewed by 515
Abstract
Flapping-wing drones (FWDs), owing to their compact size and operation in cluttered and unsteady airflow environments, encounter significant aerodynamic and stability challenges. Studies of avian flight reveal that falcons and other raptors actively deflect their covert feathers to mitigate gusts and maintain stable [...] Read more.
Flapping-wing drones (FWDs), owing to their compact size and operation in cluttered and unsteady airflow environments, encounter significant aerodynamic and stability challenges. Studies of avian flight reveal that falcons and other raptors actively deflect their covert feathers to mitigate gusts and maintain stable flight. Drawing inspiration from this mechanism, this study presents a peregrine falcon-inspired Active Flow Control Unit (AFCU) integrated with a Deep Deterministic Policy Gradient (DDPG)-based deep reinforcement learning (DRL) controller for real-time disturbance attenuation. The AFCU employs mechanical covert feathers (MCFs) that actuate to dissipate gust loads during high wind conditions. A reduced-order bond graph model that encapsulates the nonlinear interaction between the primary wing and the feather-based active flow control surfaces is created which is used as a dynamic training environment for the DDPG agent. Utilizing closed-loop interactions, the successfully obtained learned policy produces optimal actuator forces to reduce feather-displacement error and aerodynamic load variations. The designed controller stabilizes the internally unstable open-loop AFCU, attaining near-zero steady-state error and settling times under 1.6 s for gust magnitudes ranging from 12.5 to 20 m/s. Simulations further illustrate a reduction of up to 50% in gust-induced loads compared to traditional approaches. This integration of bio-inspired design with learning-based active flow control offers a viable avenue for the development of highly adaptive and gust-resilient flapping-wing aerial systems. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)
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13 pages, 3991 KB  
Article
Active Flow Control by Coanda Actuators for Aerodynamic Drag Reduction in a European-Type Truck
by R. Bardera, J. C. Matías-García, E. Barroso-Barderas, J. Fernández-Antón and A. A. Rodríguez-Sevillano
Actuators 2025, 14(11), 556; https://doi.org/10.3390/act14110556 - 13 Nov 2025
Cited by 1 | Viewed by 1366
Abstract
Heavy vehicles present high aerodynamic drag. This results in significant fuel consumption and, consequently, high emissions of harmful substances. This study examines the variation in aerodynamic drag in a European-type truck with different trailer configurations. Passive flow control by geometry modifications of the [...] Read more.
Heavy vehicles present high aerodynamic drag. This results in significant fuel consumption and, consequently, high emissions of harmful substances. This study examines the variation in aerodynamic drag in a European-type truck with different trailer configurations. Passive flow control by geometry modifications of the rear part of the trailer and active flow control using the Coanda effect were tested, with the aim of improving the aerodynamic efficiency of the vehicle. To achieve this, a modular structure of a 1:30 scaled truck was designed to enable different trailer configurations. Drag measurements were performed with a two-component external balance, and PIV tests were conducted to correlate the drag reduction with the aerodynamic changes behind the trailer. Passive control reduced drag by up to 5.7%, and active flow control reduced it by up to 12.6% compared to the unmodified base trailer. PIV flow visualization confirms that blowing effectively reduces the recirculation zone behind the trailer. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)
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19 pages, 8125 KB  
Article
Flow Separation Delay Mechanism and Aerodynamic Enhancement via Optimized Flow Deflector Configurations
by Shengguan Xu, Siyi Wang, Hongquan Chen, Jianfeng Tan, Wei Li and Shuai Yin
Actuators 2025, 14(9), 428; https://doi.org/10.3390/act14090428 - 31 Aug 2025
Cited by 1 | Viewed by 1342
Abstract
This study explores the critical role of the flow deflector in suppressing boundary layer separation and enhancing aerodynamic efficiency through systematic geometric parameterization and computational analysis. By defining eight key design variables, this research identifies optimal configurations that significantly delay flow separation at [...] Read more.
This study explores the critical role of the flow deflector in suppressing boundary layer separation and enhancing aerodynamic efficiency through systematic geometric parameterization and computational analysis. By defining eight key design variables, this research identifies optimal configurations that significantly delay flow separation at high angles of attack. Computational Fluid Dynamics (CFD) simulations reveal that optimized deflector geometries enhance suction peaks near the airfoil leading edge, redirect separated flow toward the upper surface, and inject momentum into the boundary layer to generate a more positive lift coefficient. The numerical results demonstrate that the optimized design achieves a 58.4% increase in lift coefficient and an 83.3% improvement in the lift–drag ratio by effectively mitigating large-scale vortical structures inherent in baseline configurations. Sensitivity analyses further highlight threshold-dependent “sudden-jump” behaviors in lift coefficients for parameters such as element spacing and deflection angles, while thickness exhibits minimal influence. Additionally, pre-stall optimizations show that strategically aligned deflectors preserve baseline performance with a 0.4% lift gain, whereas misaligned configurations degrade aerodynamic efficiency by up to 9.1%. These findings establish a direct correlation between deflector-induced flow redirection and separation suppression, offering actionable insights for passive flow control in stalled regimes. This research advances fundamental understanding of flow deflector-based separation management and provides practical guidelines for enhancing aerodynamic performance in aerospace applications. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)
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24 pages, 6389 KB  
Article
Local Heat Transfer Analysis of Dual Sweeping Jet, Double Sweeping Jets, and Double Circular Jets Impinging at a Flat Surface
by Muhammad Zubair, Feng Ren and Xin Wen
Actuators 2025, 14(3), 109; https://doi.org/10.3390/act14030109 - 21 Feb 2025
Viewed by 1391
Abstract
A sweeping jet is commonly preferred over a steady jet owing to its ability to better cool the region away from the strong core of an impinging jet. For industrial applications, it is important to study the thermal fields of oscillating jets in [...] Read more.
A sweeping jet is commonly preferred over a steady jet owing to its ability to better cool the region away from the strong core of an impinging jet. For industrial applications, it is important to study the thermal fields of oscillating jets in a multi-jet configuration to focus on the region that falls between the two consecutive fluidic oscillators and, hence, suggest a mechanism to uniformly cool the targeted flat surface. A comparative experimental study of dual sweeping jets (DSJs), double sweeping jets (DbSJs), and double circular jets (DbCJs) was conducted at different jet-to-plate spacings, various Re numbers, and three aspect ratios. The multi-circular and sweeping jets were impinged on a flat hot surface, which was heated at a constant flux of current, and thermocouples were employed to efficiently collect the time-averaged heat transfer distribution along the sweeping and transverse directions. It was determined that heat transfer, in terms of the Nusselt number, generally increased with increasing Re number and reduced the jet-to-wall spacing for the DSJ, DbSJ, and DbCJ, with some minor exceptions. The relative performance of these fluidic devices suggested that the best performance of DSJ was at small spacing and higher Re, DbSJ at moderate spacing and lower Re, and DbCJ at moderate spacing and moderate Re. The mutual comparison showed that along the sweeping motion, in the central region, DbCJ was better than both DSJ and DbSJ; in the right region, DSJ performance was far better than DbCJ and DbSJ; in the left region, DSJ was better than DbSJ when comparing the respective centers of DSJ and DbSJ. The dominance of DSJ over DbSJ at the centers of their respective bodies even extends in the transverse direction. Finally, for higher aspect ratios, the DSJ performed better in the outer regions, while the DbSJ performed well in the central region. Similarly, for both DSJ and DbSJ unanimously, the effect of changing the aspect ratio is interesting as initially, the Nu values increase for a higher aspect ratio, but by increasing the AR further, it causes a divergence of the fluidic volume from the central region to the surrounding region. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)
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23 pages, 8016 KB  
Article
Flow Characteristics of a Dual Sweeping Jet Impinging on a Flat Surface
by Muhammad Zubair and Xin Wen
Actuators 2025, 14(2), 101; https://doi.org/10.3390/act14020101 - 19 Feb 2025
Cited by 2 | Viewed by 1244
Abstract
The dual sweeping jet (DSJ)-producing fluidic oscillator is a novel device developed by sharing a feedback channel between two standard fluidic oscillators. This device produces a pair of sweeping jets in the outer domain and has the potential to be used for the [...] Read more.
The dual sweeping jet (DSJ)-producing fluidic oscillator is a novel device developed by sharing a feedback channel between two standard fluidic oscillators. This device produces a pair of sweeping jets in the outer domain and has the potential to be used for the better and uniform treatment of impinged surfaces. Therefore, it is important to investigate the extent of the synchronicity of these jets at different Re numbers and various aspect ratios in outer domains, and to comprehend their internal switching mechanism simultaneously. The time-averaged flow fields demonstrated that, at lower Re numbers, both sweeping jets were symmetric about their centerlines and the cores were strong. The strength of the cores deteriorated at higher Re numbers, and the flare regions became wider and stronger. Moreover, the transverse velocities pulled the sweeping jets away from the origin and a high upwash flow formed in-between the jets. The phase-averaged flow fields vividly illustrated the sharing mechanism between the two power nozzles through the formation of left- and right-loops consecutively in the shared feedback channel. These primary loops generated an auxiliary mechanism on both sides of a fluidic oscillator, which actually controlled the synchronicity of the two sweeping jets in the outer domain. Additionally, they also showed that both jets are properly synchronized and have strong cores at lower Re numbers. However, at higher Re numbers, greater velocities were found in the switching and sweeping mechanisms which caused asynchrony between the sweeping jets but nonetheless impinged a larger area and covered the region in-between the jets properly. The power nozzles were also found to self-feed themselves due to the hindrance at the ‘outer shoulders’ of this fluidic oscillator and hence caused the premature formation of a recirculation bubble of vorticity between the power nozzle and its respective outer island. Lastly, the aspect ratio analysis revealed that the asynchrony of DSJ at higher Re numbers can be mitigated by reducing the aspect ratio. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)
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Review

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55 pages, 6845 KB  
Review
Microfluidic Droplet Splitting in T-Junction: State of the Art in Actuation and Flow Manipulation
by Xiena M. Salem, Laisha Y. Rincones, Esperanza Moreno, Richard O. Adansi, Sohail M. A. K. Mohammed, Md Mahamudur Rahman and Piyush Kumar
Actuators 2026, 15(2), 96; https://doi.org/10.3390/act15020096 - 3 Feb 2026
Cited by 1 | Viewed by 1448
Abstract
Droplet-based microfluidics has emerged as a powerful platform for precise fluid manipulation in biomedical, chemical, and material science applications. Among various geometries, T-junction microchannels are widely utilized for droplet generation and splitting due to their simplicity and reliability. This review provides a comprehensive [...] Read more.
Droplet-based microfluidics has emerged as a powerful platform for precise fluid manipulation in biomedical, chemical, and material science applications. Among various geometries, T-junction microchannels are widely utilized for droplet generation and splitting due to their simplicity and reliability. This review provides a comprehensive overview of droplet splitting mechanisms in T-junction microfluidic systems, with particular emphasis on the role of actuation methods in enhancing control and functionality. We first discuss the fundamental physics governing droplet behavior, including the influence of capillary and viscous forces, flow regimes, and geometric parameters. Passive strategies based on flow rate tuning and channel design are outlined, followed by an in-depth examination of active actuation techniques: thermal, electrical, magnetic, acoustic, and pneumatic and their effects on droplet dynamics. In addition, the review highlights computational modeling approaches and experimental tools used to characterize and predict splitting behavior. Finally, we explore the current challenges and future directions in integrating multifunctional actuation systems for real-time, programmable droplet control in lab-on-a-chip platforms. This article serves as a foundational resource for researchers aiming to advance microfluidic droplet manipulation through actuator-enabled strategies. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications—3rd Edition)
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