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Hanifi, Ardeshir, DocentORCID iD iconorcid.org/0000-0002-5913-5431
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Publications (10 of 100) Show all publications
Borodulin, V. I., Ivanov, A. V., Kachanov, Y. S., Mischenko, D. A., Örlü, R., Hanifi, A. & Hein, S. (2019). Experimental and theoretical study of swept-wing boundary-layer instabilities. Unsteady crossflow instability. Physics of fluids, 31(6), Article ID 064101.
Open this publication in new window or tab >>Experimental and theoretical study of swept-wing boundary-layer instabilities. Unsteady crossflow instability
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2019 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 31, no 6, article id 064101Article in journal (Refereed) Published
Abstract [en]

Extensive combined experimental and theoretical investigations of the linear evolution of unsteady (in general) Cross-Flow (CF) and three-dimensional (3D) Tollmien-Schlichting (TS) instability modes of 3D boundary layers developing on a swept airfoil section have been carried out. CF-instability characteristics are investigated in detail at an angle of attack of -5 degrees when this kind of instability dominates in the laminar-turbulent transition process, while the 3D TS-instability characteristics are studied at an angle of attack of +1.5 degrees when this kind of instability is predominant in the transition process. All experimental results are deeply processed and compared with results of calculations based on several theoretical approaches. For the first time, very good quantitative agreement of all measured and calculated stability characteristics of swept-wing boundary layers is achieved both for unsteady CF- and 3D TS-instability modes for the case of a boundary layer developing on a real swept airfoil. The first part of the present study (this paper) is devoted to the description of the case of CF-dominated transition, while the TS-dominated case will be described in detail in a subsequent second part of this investigation.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-255496 (URN)10.1063/1.5094609 (DOI)000474440800020 ()2-s2.0-85067248795 (Scopus ID)
Note

QC 20190919

Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-09-19Bibliographically approved
Kleine, V., Kleusberg, E., Hanifi, A. & Henningson, D. S. (Eds.). (2019). Tip-vortex instabilities of two in-line wind turbines. Institute of Physics (IOP)
Open this publication in new window or tab >>Tip-vortex instabilities of two in-line wind turbines
2019 (English)Conference proceedings (editor) (Refereed)
Place, publisher, year, edition, pages
Institute of Physics (IOP), 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-251408 (URN)
Note

QC 20190619

Available from: 2019-05-14 Created: 2019-05-14 Last updated: 2019-06-19Bibliographically approved
Shahriari, N., Kollert, M. R. & Hanifi, A. (2018). Control of a swept-wing boundary layer using ring-type plasma actuators. Journal of Fluid Mechanics, 844, 36-60
Open this publication in new window or tab >>Control of a swept-wing boundary layer using ring-type plasma actuators
2018 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 844, p. 36-60Article in journal (Refereed) Published
Abstract [en]

Application of ring-type plasma actuators for control of laminar-turbulent transition in a swept-wing boundary layer is investigated thorough direct numerical simulations. These actuators induce a wall-normal jet in the boundary layer and can act as virtual roughness elements. The flow configuration resembles experiments by Kim et al. (2016 Technical Report. BUTERFLI Project TR D3.19, http://eprints.nottingham.ac.uk/id/eprint/46529). The actuators are modelled by the volume forces computed from the experimentally measured induced velocity field at the quiescent air condition. Stationary and travelling cross-flow vortices are triggered in the simulations by means of surface roughness and random unsteady perturbations. Interaction of vortices generated by actuators with these perturbations is investigated in detail. It is found that, for successful transition control, the power of the actuators should be increased to generate jet velocities that are one order of magnitude higher than those used in the experiments by Kim et al. (2016) mentioned above.

Place, publisher, year, edition, pages
Cambridge University Press, 2018
Keywords
boundary layer control, boundary layer stability, transition to turbulence
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-227547 (URN)10.1017/jfm.2018.195 (DOI)000448727700001 ()2-s2.0-85044771928 (Scopus ID)
Funder
Swedish e‐Science Research Center
Note

QC 20180517

Available from: 2018-05-17 Created: 2018-05-17 Last updated: 2018-11-14Bibliographically approved
Dadfar, R., Hanifi, A. & Henningson, D. S. (2018). Control of instabilities in an unswept wing boundary layer. AIAA Journal, 56(5), 1750-1759
Open this publication in new window or tab >>Control of instabilities in an unswept wing boundary layer
2018 (English)In: AIAA Journal, ISSN 0001-1452, E-ISSN 1533-385X, Vol. 56, no 5, p. 1750-1759Article in journal (Refereed) Published
Abstract [en]

Linear control theory is used to construct an output feedback controller to attenuate the amplitude of the Tollmien–Schlichting waves inside the boundary layer developing over an unswept wing. The analysis is based on direct numerical simulations. The studied scenario includes the impulse response of the system to a generic disturbance in the freestream, which triggers a Tollmien–Schlichting wave packet inside the boundary layer. The performance of a linear quadratic Gaussian controller is analyzed to suppress the amplitude of the Tollmien–Schlichting wave packet using a row of sensors and plasma actuators localized at the wall. The target of the controller is chosen as a subset of proper orthogonal decomposition modes describing the dynamics of the unstable disturbances. The plasma actuators are implemented as volume forcing. To account for the limitations of the plasma actuators concerning a unidirectional forcing, several strategies are implemented in the linear quadratic Gaussian framework. Their performances are compared with that for classical linear quadratic Gaussian controller. These controllers successfully reduced the amplitude of the wave packet.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics Inc., 2018
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-228955 (URN)10.2514/1.J056415 (DOI)000432661400005 ()2-s2.0-85046622897 (Scopus ID)
Funder
Swedish e‐Science Research Center
Note

QC 20180530

Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2018-06-25Bibliographically approved
Morra, P., Sasaki, K., Cavalieri, A., Hanifi, A. & Henningson, D. S. (2018). Control of streaky disturbances in the boundary layer over a flat plate. In: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018: . Paper presented at 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018, 9 September 2018 through 14 September 2018. International Council of the Aeronautical Sciences
Open this publication in new window or tab >>Control of streaky disturbances in the boundary layer over a flat plate
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2018 (English)In: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018, International Council of the Aeronautical Sciences , 2018Conference paper, Published paper (Refereed)
Abstract [en]

The present work considers control of perturbations in the boundary layer over a flat plate by means of adaptive methods. In particular, we focus our attention on a control law based on a multi-input-multi-output (MIMO) filtered-x least-mean-square (fxLMS) adaptive algorithm. The studies are performed through direct numerical simulations. The perturbation field studied here mimics those generated by freestream turbulence with different amplitude and scales. Plasma actuators and shear-stress sensors are considered to mimic a real case scenario.

Place, publisher, year, edition, pages
International Council of the Aeronautical Sciences, 2018
Keywords
Adaptive control, Feedforward control, Flow control, Streaks, Adaptive algorithms, Boundary layers, MIMO systems, Shear stress, Wave plasma interactions, Adaptive methods, Filtered x least mean squares, Freestream turbulence, Multi input multi output, Real case scenarios, Shear-stress sensors
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-247422 (URN)2-s2.0-85060468653 (Scopus ID)9783932182884 (ISBN)
Conference
31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018, 9 September 2018 through 14 September 2018
Note

QC20190502

Available from: 2019-05-02 Created: 2019-05-02 Last updated: 2019-05-02Bibliographically approved
Borodulin, V. I., Ivanov, A. V., Kachanov, Y. S., Mischenko, D. A., Örlü, R., Hanifi, A. & Hein, S. (2018). Excitation of 3D TS-waves in a swept-wing boundary layer by surface vibrations and freestream vortices. In: AIP Conference Proceedings: . Paper presented at 19th International Conference on the Methods of Aerophysical Research, ICMAR 2018, 13 August 2018 through 19 August 2018. American Institute of Physics Inc.
Open this publication in new window or tab >>Excitation of 3D TS-waves in a swept-wing boundary layer by surface vibrations and freestream vortices
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2018 (English)In: AIP Conference Proceedings, American Institute of Physics Inc. , 2018Conference paper, Published paper (Refereed)
Abstract [en]

There are several kinds of velocity disturbances, which may affect the transition to turbulence in a swept wing boundary layer. Tollmien-Schlichting (TS) waves are among most important of them. The properties of TS waves and their potential competition with cross-flow waves on a swept wing are poorly studied in theoretical works and were not studied experimentally at all. This paper presents the method of excitation of fully controlled 3D TS waves via interaction of free-stream vortices and surface vibrations. The experimental approach developed here will be used for investigation of the corresponding receptivity problem.

Place, publisher, year, edition, pages
American Institute of Physics Inc., 2018
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-247077 (URN)10.1063/1.5065230 (DOI)000481675800152 ()2-s2.0-85056347707 (Scopus ID)9780735417472 (ISBN)
Conference
19th International Conference on the Methods of Aerophysical Research, ICMAR 2018, 13 August 2018 through 19 August 2018
Note

QC 20190503

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-09-05Bibliographically approved
Kachanov, Y. S., Borodulin, V. I., Ivanov, A. V., Mischenko, D. A., Örlü, R., Hanifi, A. & Hein, S. (2018). Generation of unsteady CF-instability modes by vibrational and vibration-vortex localized receptivity mechanisms. In: AIP Conference Proceedings: . Paper presented at 19th International Conference on the Methods of Aerophysical Research, ICMAR 2018, 13 August 2018 through 19 August 2018. American Institute of Physics Inc.
Open this publication in new window or tab >>Generation of unsteady CF-instability modes by vibrational and vibration-vortex localized receptivity mechanisms
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2018 (English)In: AIP Conference Proceedings, American Institute of Physics Inc. , 2018Conference paper, Published paper (Refereed)
Abstract [en]

The paper is based on results obtained within an international project 'RECEPT' of the European Framework Program FP7. The experiments were carried out in a three-dimensional boundary layer developing on an experimental model of a long-laminar-run swept airfoil (sweep angle of 35°). The model was mounted in a test section of the low-turbulence wind-tunnel MTL (KTH, Stockholm) at an angle of attack of -5°and equipped with sidewalls provided satisfaction of infinite-span conditions. The cross-flow (CF) instability modes were predominant in this case, while the Tollmien-Schlichting (TS) waves were suppressed by a favorable pressure gradient. The main measurements were carried out by means of hot-wire anemometry at conditions of excitation of fully controlled, unsteady surface and flow perturbations. These perturbations were excited by special sources: (1) a row of oscillating membranes and (2) a vibrating cwire, at frequencies of f s and f v , respectively. A very good, quantitative agreement between the measured and calculated (by linear stability theory based on PSE approach) amplification curves was found at surface frequency f s . However, the evolution of the CF-modes excited at difference combination frequency f sv- = f s - f v turned out to be very much different from the theoretical one. Thorough analysis of the obtained results has shown that the only explanation of these discrepancies can be associated with presence of a distributed receptivity mechanism due to scattering of freestream vortices on the CF-instability waves excited by surface vibrations. Another unusual and unexpected phenomenon found in the present experiments is associated with anomalous amplification of difference combination modes with the zero spanwise wavenumbers β′. This phenomenon was observed in the flow, which is stable with respect to both CF- and TS-waves having β′ = 0 for all frequencies. There is no explanation of this finding at present.

Place, publisher, year, edition, pages
American Institute of Physics Inc., 2018
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-247078 (URN)10.1063/1.5065088 (DOI)000481675800010 ()2-s2.0-85056317829 (Scopus ID)9780735417472 (ISBN)
Conference
19th International Conference on the Methods of Aerophysical Research, ICMAR 2018, 13 August 2018 through 19 August 2018
Note

QC 20190503

Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-09-05Bibliographically approved
Negi, P. S., Hanifi, A. & Henningson, D. S. (2018). LES of the unsteady response of a natural laminar flow airfoil. In: 2018 Applied Aerodynamics Conference: . Paper presented at 36th AIAA Applied Aerodynamics Conference, 2018, [state] GA, United States, 25 June 2018 through 29 June 2018. American Institute of Aeronautics and Astronautics
Open this publication in new window or tab >>LES of the unsteady response of a natural laminar flow airfoil
2018 (English)In: 2018 Applied Aerodynamics Conference, American Institute of Aeronautics and Astronautics, 2018Conference paper, Published paper (Refereed)
Abstract [en]

Large-eddy simulations are performed to investigate the dynamic response of a natural laminar flow airfoil undergoing harmonic pitch oscillations at a chord based Reynolds number of Rec= 750, 000. Large changes in the transition location are observed throughout the pitch cycles which leads to a non-linear response of the aerodynamic force coefficients. Preliminary results show that the evolution of the boundary layer over the airfoil can be modeled by using a simple phase-lag concept which implies that the boundary-layer evolution is quasi-steady in nature. A simple empirical model is developed based on this quasi-steady, phase-lag assumption which fits very well with the measured experimental data.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2018
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-234512 (URN)10.2514/6.2018-3824 (DOI)2-s2.0-85051738799 (Scopus ID)9781624105593 (ISBN)
Conference
36th AIAA Applied Aerodynamics Conference, 2018, [state] GA, United States, 25 June 2018 through 29 June 2018
Funder
VINNOVAEU, European Research CouncilSwedish e‐Science Research Center
Note

QC 20180907

Available from: 2018-09-07 Created: 2018-09-07 Last updated: 2018-09-07Bibliographically approved
De Aguiar Quintanilha Junior, H. R., Kataras, P. B., Theofilis, V. & Hanifi, A. (2018). Nonmodal stability analysis of the HIFiRE-5 elliptic cone model flow in different flight altitudes. In: 58th Israel Annual Conference on Aerospace Sciences, IACAS 2018: . Paper presented at 58th Israel Annual Conference on Aerospace Sciences, IACAS 2018, 14 March 2018 through 15 March 2018 (pp. 1543-1555). Israel Annual Conference on Aerospace Sciences
Open this publication in new window or tab >>Nonmodal stability analysis of the HIFiRE-5 elliptic cone model flow in different flight altitudes
2018 (English)In: 58th Israel Annual Conference on Aerospace Sciences, IACAS 2018, Israel Annual Conference on Aerospace Sciences , 2018, p. 1543-1555Conference paper, Published paper (Refereed)
Abstract [en]

Nonmodal instability analysis is carried out for a 2:1 elliptic cone with base flow conditions selected for a Ma=7 and two different ight altitudes, namely 33km and 21km with unit Reynolds number Re′ = 1.89 x 106 m-1 and Re′ = 1.015 x 107 m-1, respectively. The aim is to analyze the effects of transiently growing optimal disturbances and their possible relation to instability mechanisms that have been confirmed to exist in previous modal crossow. Local linear stability results obtained at several streamwise locations on the cone surface indicate that transient growth in the crossow region may be correlated to streamwise oriented structures having spanwise spacing of the same order of magnitude as which have long been known to exist in this flow.

Place, publisher, year, edition, pages
Israel Annual Conference on Aerospace Sciences, 2018
Keywords
Aerospace engineering, Cones, Reynolds equation, Reynolds number, Flight altitudes, Instability analysis, Instability mechanisms, Optimal disturbances, Oriented structure, Stability analysis, Streamwise locations, Transient growth, Stability
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-236404 (URN)2-s2.0-85048983459 (Scopus ID)
Conference
58th Israel Annual Conference on Aerospace Sciences, IACAS 2018, 14 March 2018 through 15 March 2018
Note

QC 20181031

Available from: 2018-10-31 Created: 2018-10-31 Last updated: 2018-10-31Bibliographically approved
Sasaki, K., Morra, P., Fabbiane, N., Cavalieri, A. V. G., Hanifi, A. & Henningson, D. S. (2018). On the wave-cancelling nature of boundary layer flow control. Theoretical and Computational Fluid Dynamics, 32(5), 593-616
Open this publication in new window or tab >>On the wave-cancelling nature of boundary layer flow control
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2018 (English)In: Theoretical and Computational Fluid Dynamics, ISSN 0935-4964, E-ISSN 1432-2250, Vol. 32, no 5, p. 593-616Article in journal (Refereed) Published
Abstract [en]

This work deals with the feedforward active control of Tollmien-Schlichting instability waves over incompressible 2D and 3D boundary layers. Through an extensive numerical study, two strategies are evaluated; the optimal linear-quadratic-Gaussian (LQG) controller, designed using the Eigensystem realization algorithm, is compared to a wave-cancellation scheme, which is obtained using the direct inversion of frequency-domain transfer functions of the system. For the evaluated cases, it is shown that LQG leads to a similar control law and presents a comparable performance to the simpler, wave-cancellation scheme, indicating that the former acts via a destructive interference of the incoming wavepacket downstream of actuation. The results allow further insight into the physics behind flow control of convectively unstable flows permitting, for instance, the optimization of the transverse position for actuation. Using concepts of linear stability theory and the derived transfer function, a more efficient actuation for flow control is chosen, leading to similar attenuation of Tollmien-Schlichting waves with only about 10% of the actuation power in the baseline case.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Boundary layer control, Flow control, Instability control, LQG controllers, Inversion controllers
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-235102 (URN)10.1007/s00162-018-0469-x (DOI)000443412500003 ()2-s2.0-85049125322 (Scopus ID)
Note

QC 20180917

Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2018-09-17Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-5913-5431

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