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Control of Dynamic Flow Fields
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Control of Dynamic Flow Fields

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F: Electrical Engineering".

Deadline for manuscript submissions: closed (31 July 2021) | Viewed by 28705

Special Issue Editor

Dr. Taku Nonomura

E-Mail Website
Guest Editor
Department of Aerospace Engineering, Graduate School of Engineering, Tohoku University, Sendai, Miyagi, Japan
Interests: aerospace engineering; fluid dynamics; aeroacoustics; flow control; reduced order modeling
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

For several decades, the control of dynamic flow fields has been investigated by experiments and numerical simulations, but applications-based advanced flow control such as active and reactive flow control, which seems to be more effective, has been limited. There have been difficulties owing to (1) a lack of knowledge of complex fluid dynamics, (2) the high cost of simulations for the state-space model, and (3) the absence of appropriate flow sensor and control devices that work with small latency. However, recently high-fidelity experiments and numerical simulations have been made available for (1) a more detailed understanding of the flow fields to address and (2) reduced order modeling or machine learning to run the model simulating the simplified flow that the model has been developed to resolve. In addition to these resolutions, (3) the appropriate flow control devices with small latency, such as plasma actuators and synthetic jets, have become available. Based on the three advances mentioned above, now is a great opportunity to advance research on the control of dynamic flow fields. To accelerate the efforts on the control of dynamic flow fields, we would like to organize the Special Issue "Control of Dynamic Flow Fields", in Energy. This Special Issue welcomes, but is not limited to, papers related to any of the three kinds of efforts for flow control:

(1) A detailed analysis of dynamic flow control based on high-fidelity experiments and numerical simulations, such as

  • Advanced measurements, such as dynamic particle image velocimetry, for controlled flow fields;
  • High-fidelity simulations, such as direct numerical simulations or large-eddy simulations for controlled flow fields.

(2) Reduced order modeling or machine learning to run advanced flow control algorithms such as

  • Modal decompositions for modeling controlled flow fields based on the data-driven approach;
  • Discourteous Galerkin projection for modeling based on the analytical approach;
  • Machine learning such as deep neural networks for flow control algorithms.

(3) Dynamic flow control results using advanced flow control devices, such as plasma actuators such as

  • Active flow control using plasma actuators;
  • Active flow control using synthetic jets.

Prof. Dr. Taku Nonomura
Guest Editor

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Keywords

  • dynamic flow fields
  • numerical simulations
  • active and reactive flow control
  • complex fluid dynamics
  • plasma actuators
  • synthetic jets
  • machine learning

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Published Papers (9 papers)

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Research

17 pages, 1616 KiB  
Article
Dynamic Stall Control around Practical Airfoil Using Nanosecond-Pulse-Driven Dielectric Barrier Discharge Plasma Actuators
by Yuto Iwasaki, Taku Nonomura, Koki Nankai, Keisuke Asai, Shoki Kanno, Kento Suzuki, Atsushi Komuro, Akira Ando, Keisuke Takashima, Toshiro Kaneko, Hidemasa Yasuda, Kenji Hayama, Tomoka Tsujiuchi, Tsutomu Nakajima and Kazuyuki Nakakita
Energies 2020, 13(6), 1376; https://doi.org/10.3390/en13061376 - 16 Mar 2020
Cited by 12 | Viewed by 2996
Abstract
The flow control effects of a nanosecond-pulse-driven dielectric barrier discharge plasma actuator (ns-DBDPA) in dynamic stall flow were experimentally investigated. The ns-DBDPA was installed on the leading edge of an airfoil model designed in the form of a helicopter blade. The model was [...] Read more.
The flow control effects of a nanosecond-pulse-driven dielectric barrier discharge plasma actuator (ns-DBDPA) in dynamic stall flow were experimentally investigated. The ns-DBDPA was installed on the leading edge of an airfoil model designed in the form of a helicopter blade. The model was oscillated periodically around 25% of the chord length. Aerodynamic coefficients were calculated using the pressure distribution, which was obtained by the measurement of the unsteady pressure by sensors inside the model. The flow control effect and its sensitivity to pitching oscillation and ns-DBDPA control parameters are discussed using the aerodynamic coefficients. The freestream velocity, the mean of the angle of attack, and the reduced frequency were employed as the oscillation parameters. Moreover, the nondimensional frequency of the pulse voltage, the peak pulse voltage, and the type and position of the ns-DBDPA were adopted as the control parameters. The result shows that the ns-DBDPA can decrease the hysteresis of the aerodynamic coefficients and a flow control effect is obtained in all cases. The flow control effect can be maximized by adopting the low nondimensional frequency of the pulse voltage. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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20 pages, 1341 KiB  
Article
Stall Control by Plasma Actuators: Characterization along the Airfoil Span
by Giulia Zoppini, Marco Belan, Alex Zanotti, Lorenzo Di Vinci and Giuseppe Campanardi
Energies 2020, 13(6), 1374; https://doi.org/10.3390/en13061374 - 16 Mar 2020
Cited by 6 | Viewed by 2752
Abstract
A dielectric barrier discharge actuator (DBD) is considered and studied as a stall recovery device. The DBD is installed on the nose of a NACA0015 airfoil with chord × span 300 × 930 mm. The geometry of the exposed electrode has periodic triangular [...] Read more.
A dielectric barrier discharge actuator (DBD) is considered and studied as a stall recovery device. The DBD is installed on the nose of a NACA0015 airfoil with chord × span 300 × 930 mm. The geometry of the exposed electrode has periodic triangular tips purposely designed for the case under study. Wind tunnel tests have been carried out over a range of airspeeds up to 35 m/s with a Reynolds number of 700 k. The flow morphology has been characterized by means of the particle image velocimetry technique, obtaining velocity fields and pressure coefficients. By exploring different planes along the model span, the three-dimensional effect of the DBD has been reconstructed, identifying the flow region mainly sensitive to the plasma actuation. Finally, the actuator effectiveness has been quantified accounting for the power consumption data, leading to defining further design improvements in view of a better efficiency. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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24 pages, 3495 KiB  
Article
Designs of Feedback Controllers for Fluid Flows Based On Model Predictive Control and Regression Analysis
by Yasuo Sasaki and Daisuke Tsubakino
Energies 2020, 13(6), 1325; https://doi.org/10.3390/en13061325 - 12 Mar 2020
Cited by 7 | Viewed by 2553
Abstract
Complexity of online computation is a drawback of model predictive control (MPC) when applied to the Navier–Stokes equations. To reduce the computational complexity, we propose a method to approximate the MPC with an explicit control law by using regression analysis. In this paper, [...] Read more.
Complexity of online computation is a drawback of model predictive control (MPC) when applied to the Navier–Stokes equations. To reduce the computational complexity, we propose a method to approximate the MPC with an explicit control law by using regression analysis. In this paper, we extracted two state-feedback control laws and two output-feedback control laws for flow around a cylinder as a benchmark. The state-feedback control laws that feed back different quantities to each other were extracted by ridge regression, and the two output-feedback control laws, whose measurement output is the surface pressure, were extracted by ridge regression and Gaussian process regression. In numerical simulations, the state-feedback control laws were able to suppress vortex shedding almost completely. While the output-feedback control laws could not suppress vortex shedding completely, they moderately improved the drag of the cylinder. Moreover, we confirmed that these control laws have some degree of robustness to the change in the Reynolds number. The computation times of the control input in all the extracted control laws were considerably shorter than that of the MPC. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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16 pages, 3883 KiB  
Article
Separated Flow Control of Small Horizontal-Axis Wind Turbine Blades Using Dielectric Barrier Discharge Plasma Actuators
by Hikaru Aono, Hiroaki Fukumoto, Yoshiaki Abe, Makoto Sato, Taku Nonomura and Kozo Fujii
Energies 2020, 13(5), 1218; https://doi.org/10.3390/en13051218 - 6 Mar 2020
Cited by 12 | Viewed by 3884
Abstract
The flow control over the blades of a small horizontal-axis wind turbine (HAWT) model using a dielectric barrier discharge plasma actuator (DBD-PA) was studied based on large-eddy simulations. The numerical simulations were performed with a high-resolution computational method, and the effects of the [...] Read more.
The flow control over the blades of a small horizontal-axis wind turbine (HAWT) model using a dielectric barrier discharge plasma actuator (DBD-PA) was studied based on large-eddy simulations. The numerical simulations were performed with a high-resolution computational method, and the effects of the DBD-PA on the flow fields around the blades were modeled as a spatial body force distribution. The DBD-PA was installed at the leading edge of the blades, and its impacts on the flow fields and axial torque generation were discussed. The increase in the ratios of the computed, cycle-averaged axial torque reasonably agreed with that of the available experimental data. In addition, the computed results presented a maximum of 19% increase in the cycle-averaged axial torque generation by modulating the operating parameters of the DBD-PA because of the suppression of the leading edge separation when the blade’s effective angles of attack were relatively high. Thus, the suppression of the leading edge separation by flow control can lead to a delay in the breakdown of the tip vortex as a secondary effect. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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20 pages, 12056 KiB  
Article
Effects of Jet Induced by String-type Plasma Actuator on Flow Around Three-Dimensional Bluff Body and Drag Force
by Takatoshi Matsubara, Yoshiki Shima, Hikaru Aono, Hitoshi Ishikawa and Takehiko Segawa
Energies 2020, 13(4), 872; https://doi.org/10.3390/en13040872 - 17 Feb 2020
Cited by 3 | Viewed by 2698
Abstract
An experimental investigation of active flow control on a three-dimensional (3D) curved surface bluff body was conducted by using a string-type plasma actuator. The 3D bluff body model tested in this study was composed of a quarter sphere and a half cylinder, and [...] Read more.
An experimental investigation of active flow control on a three-dimensional (3D) curved surface bluff body was conducted by using a string-type plasma actuator. The 3D bluff body model tested in this study was composed of a quarter sphere and a half cylinder, and the Reynolds number based on the diameter of half cylinder was set at 1.3 × 104. The modulation drive was adopted for flow control, and the control effects of variations in dimensionless burst frequency (fm+) normalized by the width of the model and freestream velocity were studied. Velocity distributions analyzed by particle image velocimetry showed that the recirculation region behind the model shrank due to the flow control. The static pressure distributions on the back surface of the model tended to decrease under any fm+ set in this study, especially in the ranges of 0.40 ≤ fm+ ≤ 0.64. The drag coefficient reached its maximum value under the similar ranges of fm+. Although the aerodynamic wake sharpening was observed due to the flow control, the entrainment of separated flow into the back surface of the model was enhanced. This scenario of wake manipulation was considered to be responsible for increasing drag acting on the model. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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12 pages, 2377 KiB  
Article
A Hybrid Model for Lift Response to Dynamic Actuation on a Stalled Airfoil
by Xuanhong An, David R. Williams and Maziar S. Hemati
Energies 2020, 13(4), 855; https://doi.org/10.3390/en13040855 - 15 Feb 2020
Viewed by 2146
Abstract
The current research focuses on modeling the lift response due to dynamic (time-varying) “burst-type” actuation on a stalled airfoil. Here, the “burst-type” actuation refers to the synthetic jet (generated from the actuator) that is used for flow separation mitigation. Dynamic “burst-type” actuation exhibits [...] Read more.
The current research focuses on modeling the lift response due to dynamic (time-varying) “burst-type” actuation on a stalled airfoil. Here, the “burst-type” actuation refers to the synthetic jet (generated from the actuator) that is used for flow separation mitigation. Dynamic “burst-type” actuation exhibits two different characteristic dynamic behaviors within the system; namely, the high-frequency and low-frequency components. These characteristics introduce modeling challenges. In this paper, we propose a hybrid model composed of two individual sub-models, one for each of the two frequencies. The lift response due to high-frequency burst actuation is captured using a convolution model. The low-frequency component due to nonlinear burst-burst interactions is captured using a Wiener model, consisting of linear time-invariant dynamics and a static output nonlinearity. The hybrid model is validated using data from wind tunnel experiments. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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23 pages, 19844 KiB  
Article
Effects of Input Voltage and Freestream Velocity on Active Flow Control of Passage Vortex in a Linear Turbine Cascade Using Dielectric Barrier Discharge Plasma Actuator
by Takayuki Matsunuma and Takehiko Segawa
Energies 2020, 13(3), 764; https://doi.org/10.3390/en13030764 - 9 Feb 2020
Cited by 6 | Viewed by 4560
Abstract
Passage vortex exists as one of the typical secondary flows in turbomachines and generates a significant total pressure loss and degrades the aerodynamic performance. Herein, a dielectric barrier discharge (DBD) plasma actuator was utilized for an active flow control of the passage vortex [...] Read more.
Passage vortex exists as one of the typical secondary flows in turbomachines and generates a significant total pressure loss and degrades the aerodynamic performance. Herein, a dielectric barrier discharge (DBD) plasma actuator was utilized for an active flow control of the passage vortex in a linear turbine cascade. The plasma actuator was installed on the endwall, 10 mm upstream from the leading edge of the turbine cascade. The freestream velocity at the outlet of the linear turbine cascade was set to range from UFS,out = 2.4 m/s to 25.2 m/s, which corresponded to the Reynolds number ranging from Reout = 1.0 × 104 to 9.9 × 104. The two-dimensional velocity field at the outlet of the linear turbine cascade was experimentally analyzed by particle image velocimetry (PIV). At lower freestream velocity conditions, the passage vortex was almost negligible as a result of the plasma actuator operation (UPA,max/UFS,out = 1.17). Although the effect of the jet induced by the plasma actuator weakened as the freestream velocity increased, the magnitude of the peak vorticity was reduced under all freestream velocity conditions. Even at the highest freestream velocity condition of UFS,out = 25.2 m/s, the peak value of the vorticity was reduced approximately 17% by the plasma actuator operation at VAC = 15 kVp-p (UPA,max/UFS,out = 0.18). Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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15 pages, 5661 KiB  
Article
Thermal Fluctuation Characteristics around a Nanosecond Pulsed Dielectric Barrier Discharge Plasma Actuator using a Frequency Analysis based on Schlieren Images
by Takahiro Ukai and Konstantinos Kontis
Energies 2020, 13(3), 628; https://doi.org/10.3390/en13030628 - 2 Feb 2020
Cited by 18 | Viewed by 3533
Abstract
A thermal fluctuation driven by a burst plasma discharge is experimentally investigated using a frequency analysis based on the Schlieren images. The burst plasma discharge is controlled by an interval frequency fint = 200 Hz and a pulse frequency fB = [...] Read more.
A thermal fluctuation driven by a burst plasma discharge is experimentally investigated using a frequency analysis based on the Schlieren images. The burst plasma discharge is controlled by an interval frequency fint = 200 Hz and a pulse frequency fB = 3.6 kHz as well as the duration time of the burst event: Ton. A burst feature is defined as a burst ratio BR = Ton/(1/fint). The burst plasma discharge generates a burst-induced hot plume growing above a ground electrode. In a high burst ratio, which is BR = 0.45 and 0.57, the burst-induced hot plume is formed as a wave thermal pattern that is mainly fluctuated at the interval frequency of 200 Hz. Additionally, a maximum fluctuation spot of 200 Hz appears near the edge of an exposed electrode in a low burst ratio, whereas it moves towards the ground electrode in the high burst ratio. The possible scenario is that a relatively strong ionic wind and/or an induced jet generated in the high burst ratio might cause the movement of the maximum fluctuation spot. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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18 pages, 8201 KiB  
Article
Feedback Control for Transition Suppression in Direct Numerical Simulations of Channel Flow
by Yiyang Sun and Maziar S. Hemati
Energies 2019, 12(21), 4127; https://doi.org/10.3390/en12214127 - 29 Oct 2019
Cited by 5 | Viewed by 2497
Abstract
For channel flow at subcritical Reynolds numbers ( R e < 5772 ), a laminar-to-turbulent transition can emerge due to a large transient amplification in the kinetic energy of small perturbations, resulting in an increase in drag at the walls. The objectives of [...] Read more.
For channel flow at subcritical Reynolds numbers ( R e < 5772 ), a laminar-to-turbulent transition can emerge due to a large transient amplification in the kinetic energy of small perturbations, resulting in an increase in drag at the walls. The objectives of the present study are three-fold: (1) to study the nonlinear effects on transient energy growth, (2) to design a feedback control strategy to prevent this subcritical transition, and (3) to examine the control mechanisms that enable transition suppression. We investigate transient energy growth of linear optimal disturbance in plane Poiseuille flow at a subcritical Reynolds number of R e = 3000 using linear analysis and nonlinear simulation. Consistent with previous studies, we observe that the amplification of the given initial perturbation is reduced when the nonlinear effect is substantial, with larger perturbations being less amplified in general. Moreover, we design linear quadratic optimal controllers to delay transition via wall-normal blowing and suction actuation at the channel walls. We demonstrate that these feedback controllers are capable of reducing transient energy growth in the linear setting. The performance of the same controllers is evaluated for nonlinear flows where a laminar-to-turbulent transition emerges without control. Nonlinear simulations reveal that the controllers can reduce transient energy growth and suppress transition. Further, we identify and characterize the underlying physical mechanisms that enable feedback control to suppress and delay laminar-to-turbulent transition. Full article
(This article belongs to the Special Issue Control of Dynamic Flow Fields)
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