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Hanifi, Ardeshir, DocentORCID iD iconorcid.org/0000-0002-5913-5431
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Publications (10 of 109) 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
Negi, P., Hanifi, A. & Henningson, D. S. (2019). Global Stability of rigid-body-motion fluid-structure-interaction problems.
Open this publication in new window or tab >>Global Stability of rigid-body-motion fluid-structure-interaction problems
2019 (English)Report (Other academic)
Abstract [en]

A rigorous derivation and validation for linear fluid-structure-interaction (FSI) equations for a rigid-body-motion problem is performed in an Eulerian framework. We show that the “added-stiffness” terms arising in the formulation of Fanion et al. (2000) vanish at the FSI interface in a first-order approximation. Several numerical tests with rigid-body motion are performed to show the validity of the derived formulation by comparing the time evolution between the linear and non-linear equations when the base flow is perturbed by identical small-amplitude perturbations. In all cases both the growth rate and angular frequency of the instability matches within 0.1% accuracy. The derived formulation is used to investigate the phenomenon of symmetry breaking for a rotating cylinder with an attached splitter-plate. The results show that the onset of symmetry breaking can be explained by the existence of a zero-frequency linearly unstable mode of the coupled fluid-structure-interaction system. Finally, the structural sensitivity of the least stable eigenvalue is studied for an oscillating cylinder, which is found to change significantly when the fluid and structural frequencies are close to resonance.

Publisher
p. 38
Series
TRITA-SCI-RAP ; 2019:007
National Category
Fluid Mechanics and Acoustics Aerospace Engineering
Research subject
Aerospace Engineering
Identifiers
urn:nbn:se:kth:diva-262856 (URN)
Funder
Swedish National Infrastructure for Computing (SNIC)
Note

QC 20191025. QC 20191030

Available from: 2019-10-23 Created: 2019-10-23 Last updated: 2019-10-30Bibliographically approved
Quintanilha, H. J., Theofilis, V. & Hanifi, A. (2019). Global transient-growth analysis of hypersonic flow on the hifire-5 elliptic cone model. In: AIAA Scitech 2019 Forum: . Paper presented at AIAA Scitech Forum, 7-11 January 2019, San Diego, California. American Institute of Aeronautics and Astronautics Inc, AIAA
Open this publication in new window or tab >>Global transient-growth analysis of hypersonic flow on the hifire-5 elliptic cone model
2019 (English)In: AIAA Scitech 2019 Forum, American Institute of Aeronautics and Astronautics Inc, AIAA , 2019Conference paper, Published paper (Refereed)
Abstract [en]

Linear global non-modal instability analysis of the boundary layer over the Hypersonic International Flight Research Experimentation 5 (HIFiRE-5) rounded-tip 2:1 elliptic cone model is performed on a plane normal to the cone symmetry axis. The base flow has been computed using the US3D solver at Ma=7 and flight altitude of 33km and has been analyzed with respect to its modal instability in earlier work. The present objective is to interrogate the same flow regarding the existence of optimal transiently growing small-amplitude disturbances and correlate the latter with exponentially-growing modal instability mechanisms that have been confirmed to exist in this flow. Perturbation energy growth is calculated here using Singular Value Decomposition (SVD) of the linearized Navies-Stokes evolution operator: local transient growth analysis is performed by linearizing about an one-dimensional profile extracted from the base flow, while global non-modal analysis is performed by performing the SVD of the operator linearized about the full two-dimensional steady state on the plane. In both cases linear optimal perturbations are computed; local results are consistent with those of earlier analysis of the compressible flat-plate boundary layer, while global transient growth analysis results obtained herein reveal both symmetric and antisymmetric global modes emerging out of the temporal integration of the linearized operator in the limit of asymptotically large times. This scenario of emergence of modal perturbations in a non-modal analysis, in which no explicit assumption of harmonic time-dependence of linear perturbations has been made, is consistent with analogous findings in a number of incompressible flows and reconciles earlier modal and non-modal linear instability analysis results obtained on the HIFiRE-5 model configuration. � 2019 by German Aerospace Center (DLR). Published by the American Institute of Aeronautics and Astronautics, Inc.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics Inc, AIAA, 2019
Keywords
Aerodynamics, Aviation, Hypersonic boundary layers, Hypersonic flow, Incompressible flow, Linearization, Singular value decomposition, Stability, Transient analysis, Warships, American Institute of Aeronautics and Astronautics, Flat plate boundary layers, German aerospace centers, Harmonic time dependence, International flights, Linear instability analysis, Linear perturbations, Temporal integration, Modal analysis
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-262461 (URN)10.2514/6.2019-2148 (DOI)2-s2.0-85068893493 (Scopus ID)9781624105784 (ISBN)
Conference
AIAA Scitech Forum, 7-11 January 2019, San Diego, California
Note

QC 20191018

Available from: 2019-10-18 Created: 2019-10-18 Last updated: 2019-10-18Bibliographically approved
Brynjell-Rahkola, M., Hanifi, A. & Henningson, D. S. (2019). On the stability of a Blasius boundary layer subject to localised suction. Journal of Fluid Mechanics, 871, 717-741
Open this publication in new window or tab >>On the stability of a Blasius boundary layer subject to localised suction
2019 (English)In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 871, p. 717-741Article in journal (Refereed) Published
Abstract [en]

In this study the origins of premature transition due to oversuction in boundary layers are studied. An infinite row of circular suction pipes that are mounted at right angles to a flat plate subject to a Blasius boundary layer is considered. The interaction between the flow originating from neighbouring holes is weak and for the parameters investigated, the pipe is always found to be unsteady regardless of the state of the flow in the boundary layer. A stability analysis reveals that the appearance of boundary layer transition can be associated with a linear instability in the form of two unstable eigenmodes inside the pipe that have weak tails, which extend into the boundary layer. Through an energy budget and a structural sensitivity analysis, the origin of this flow instability is traced to the structures developing inside the pipe near the pipe junction. Although the amplitudes of the modes in the boundary layer are orders of magnitude smaller than the corresponding amplitudes inside the pipe, a Koopman analysis of the data gathered from a nonlinear direct numerical simulation confirms that it is precisely these disturbances that are responsible for transition to turbulence in the boundary layer due to oversuction.

Place, publisher, year, edition, pages
CAMBRIDGE UNIV PRESS, 2019
Keywords
boundary layer stability, transition to turbulence
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-264150 (URN)10.1017/jfm.2019.326 (DOI)000493076600011 ()2-s2.0-85066907512 (Scopus ID)
Note

QC 20191209

Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2019-12-09Bibliographically approved
Borodulin, V. I., Ivanov, A. V., Kachanov, Y. S., Mischenko, D. A., Örlü, R., Hanifi, A. & Hein, S. (2019). Receptivity coefficients of vortex-vibrational type at excitation of 3D Tollmien-Schlichting waves in a boundary layer on a swept wing. In: HIGH-ENERGY PROCESSES IN CONDENSED MATTER (HEPCM 2019): Proceedings of the XXVI Conference on High-Energy Processes in Condensed Matter, dedicated to the 150th anniversary of the birth of S.A. Chaplygin: . Paper presented at 26th All-Russian Conference on High Energy Processes in Condensed Matter: Dedicated to the 150th Anniversary of the Birth of S.A. Chaplygin, HEPCM 2019; Novosibirsk; Russian Federation; 3 April 2019 through 5 April 2019. American Institute of Physics (AIP), Article ID 030044.
Open this publication in new window or tab >>Receptivity coefficients of vortex-vibrational type at excitation of 3D Tollmien-Schlichting waves in a boundary layer on a swept wing
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2019 (English)In: HIGH-ENERGY PROCESSES IN CONDENSED MATTER (HEPCM 2019): Proceedings of the XXVI Conference on High-Energy Processes in Condensed Matter, dedicated to the 150th anniversary of the birth of S.A. Chaplygin, American Institute of Physics (AIP), 2019, article id 030044Conference paper, Published paper (Refereed)
Abstract [en]

The paper is devoted to the first results of an experimental quantitative study of the receptivity mechanism of a swept-wing laminar boundary layer related to scattering of 2D freestream vortices (with frequency fv) at 3D local surface vibrations (with frequency fs) resulting in an excitation of Tollmien-Schlichting (TS) waves (having combination frequencies f+ = fs+fv and f- = fs - fv). The experiments were carried out in a low-turbulence level wind tunnel on a high-precision experimental model of long-laminar-run swept airfoil (sweep angle of 35°) at a freestream speed of about 10 m/s. Controlled localized 3D surface vibrations and 2D freestream vortices were generated by special disturbance sources. Quantitative characteristics of the studied receptivity mechanism (receptivity coefficients) were estimated.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
Series
AIP Conference Proceedings, ISSN 0094-243X ; 2125
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-262562 (URN)10.1063/1.5117426 (DOI)2-s2.0-85070555367 (Scopus ID)9780735418653 (ISBN)
Conference
26th All-Russian Conference on High Energy Processes in Condensed Matter: Dedicated to the 150th Anniversary of the Birth of S.A. Chaplygin, HEPCM 2019; Novosibirsk; Russian Federation; 3 April 2019 through 5 April 2019
Note

QC 20191025

Available from: 2019-10-25 Created: 2019-10-25 Last updated: 2019-10-25Bibliographically 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
Kleine, V., Kleusberg, E., Hanifi, A. & Henningson, D. S. (2019). Tip-vortex instabilities of two in-line wind turbines. In: Wake Conference 201922–24 May 2019, Visby, Sweden: . Paper presented at Wake Conference 2019; Uppsala University's Gotland Campus, Visby; Sweden; 22 May 2019 through 24 May 2019. Institute of Physics Publishing (IOPP), 1256(1), Article ID 012015.
Open this publication in new window or tab >>Tip-vortex instabilities of two in-line wind turbines
2019 (English)In: Wake Conference 201922–24 May 2019, Visby, Sweden, Institute of Physics Publishing (IOPP), 2019, Vol. 1256, no 1, article id 012015Conference paper, Published paper (Refereed)
Abstract [en]

The hydrodynamic stability of a vortex system behind two in-line wind turbines operating at low tip-speed ratios is investigated using the actuator-line method in conjunction with the spectral-element flow solver Nek5000. To this end, a simplified setup with two identical wind turbine geometries rotating at the same tip-speed ratio is simulated and compared with a single turbine wake. Using the rotating frame of reference, a steady solution is obtained, which serves as a base state to study the growth mechanisms of induced perturbations to the system. It is shown that, already in the steady state, the tip vortices of the two turbines interact with each other, exhibiting the so-called overtaking phenomenon. Hereby, the tip vortices of the upstream turbine overtake those of the downstream turbine repeatedly. By applying targeted harmonic excitations at the upstream turbine's blade tips a variety of modes are excited and grow with downstream distance. Dynamic mode decomposition of this perturbed flow field showed that the unstable out-of-phase mode is dominant, both with and without the presence of the second turbine. The perturbations of the upstream turbine's helical vortex system led to the destabilization of the tip vortices shed by the downstream turbine. Two distinct mechanisms were observed: for certain frequencies the downstream turbine's vortices oscillate in phase with the vortex system of the upstream turbine while for other frequencies a clear out-of-phase behaviour is observed. Further, short-wave instabilities were shown to grow in the numerical simulations, similar to existing experimental studies [1].

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2019
Series
Journal of Physics: Conference Series, ISSN 1742-6588
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-262574 (URN)10.1088/1742-6596/1256/1/012015 (DOI)2-s2.0-85070017009 (Scopus ID)
Conference
Wake Conference 2019; Uppsala University's Gotland Campus, Visby; Sweden; 22 May 2019 through 24 May 2019
Note

QC 20191024

Available from: 2019-10-24 Created: 2019-10-24 Last updated: 2019-10-24Bibliographically 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
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ORCID iD: ORCID iD iconorcid.org/0000-0002-5913-5431

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