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Effects of Mach numbers on Magnus induced surface pressure

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Chinese Journal of Aeronautics 2020年第12期33卷 3058-3072页

作者： F.ASKArY M.r.soltani Department of Aerospace Engineering Sharif UniversityTehran P.O.B ***Iran Department of Aeronautics and Astronautics University of WashingtonSeattle BOX 352400USA

Experimental and numerical methods were used to investigate the Magnus phenomena over a spinning *** pressure force acting on the surface of a spinning projectile was measured for various cases by employing a relatively novel experimental technique.A set of miniature pressure sensors along with a data acquisition board,battery and storage memory were placed inside a spinning model and the surface pressure were obtained through a remotely controlled *** pressures of the model for both rotational and static conditions were obtained at two different free stream Mach numbers of 0.4 and 0.8 and at different angles of *** results showed the ability of this new test method to measure the very small Magnus force via surface pressures over the *** results provide a deep insight into the flow structure and illustrate changes in the cross-flow separation locations as a result of *** results were obtained by the numerical simulations and were compared with the experimental data.

关键词： Magnus effect Spinning projectile Surface pressure Wind tunnel

Entanglement in a two-spin system with long-range interactions

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Chinese Physics B 2016年第8期25卷 369-372页

作者： soltani M r Mahdavifar S Mahmoudi M Department of Physics College of Science Yadegar-e-Imam Khomeini (RAH) Shahre-Rey Branch Islamic Azad University Department of Physics University of Guilan

The quantum entanglement between two spins in the Ising model with an added Dzyaloshinsky–Moriya（DM） interaction and in the presence of the transverse magnetic field is studied. The exchange interaction is considered as a function of the distance between spins. The negativity as a function of magnetic field, exchange and DM interaction is *** effect of the distance between spins is studied based on the negativity. In addition, the effect of the thermal fluctuation on the negativity is also investigated.

关键词： entanglement Ising model DM interaction negativity long range interaction

Experimental study of the boundary layer over an airfoil in plunging motion

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Acta Mechanica Sinica 2012年第2期28卷 372-384页

作者： F.rasi Marzabadi M.r.soltani Aerospace research Institute TehranIran Department of Aerospace Engineering Sharif University of TechnologyTehranIran

This is an experimental study on the bound- ary layer over an airfoil under steady and unsteady conditions. It specifically deals with the effect of plunging oscil- lation on the laminar/turbulent characteristics of the bound- ary layer. The wind tunnel measurements involved surface- mounted hot-film sensors and boundary-layer rake. The ex- periments were conducted at reynolds numbers of 0.42 x 106 to 0.84 X l06 and the reduced frequency was varied from 0.01 to 0.11. The results of the quasi-wall-shear stress as well as the boundary layer velocity profiles provided impor- tant information about the state of the boundary layer over the suction surface of the airfoil in both static and dynamic cases. For the static tests, boundary layer transition occurred through a laminar separation bubble. By increasing the an- gle of attack, disturbances and the transition location moved toward the leading edge. For the dynamic tests, earlier transi- tion occurred with increasing rather than decreasing effective angle of attack. The mean angle of attack and the oscillating parameters significantly affected the state of the boundary layer. By increasing the reduced frequency, the boundary layer transition was promoted to the upstroke portion of the equivalent angle of attack, but the quasi skin friction coeffi- cient was decreased.

关键词： Boundary layer Unsteady - Plunging Wind tunnel Airfoil

Impact of reduced frequency on the time lag in pressure distribution over a supercritical airfoil in a pitch-pause-return motion

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Chinese Journal of Aeronautics 2019年第2期32卷 243-252页

作者： Haghighat Z.ESLAMI Ali r.DAVArI M.r.soltani Aerospace Division Department of Engineering Science and Research Branch Islamic Azad University Department of Aerospace Engineering Sharif University of Technology

Effects of reduced frequency, stop angle, and pause duration have been studied on a thin supercritical airfoil undergoing a pitch-pause-return motion, which is one of the classic maneuvers introduced by the AIAA Fluid Dynamics Technical Committee. Experiments were conducted in a low-speed wind tunnel at both a constant mean angle of attack and an oscillation amplitude with a reduced frequency ranging from 0.01 to 0.12. The desired stop angles of the airfoil were set to occur during the upstroke motion. The unsteady pressure distribution on the airfoil was measured for below, near, and beyond static stall conditions. results showed that the reduced frequency and stop angle were the dominant contributors to the time lag in the flowfield. For stop angles in both belowand post-stall regions, the time for the flowfield to reach its steady state conditions, known as the time lag, decreased as the reduced frequency was increased. However, in the static-stall region and for a certain value of reduced frequency, a resonance phenomenon was observed, and a minimum time lag was achieved. The pressure distribution in this condition was shown to be highly influenced by this phenomenon.

关键词： Dynamic stall Pitch pause return motion reduced frequency Static stall Time lag

MULTIPLIEr OPErATOrS AND EXTrEMAL FUNCTIONS rELATED TO THE DUAL DUNKL-SONINE OPErATOr

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Acta Mathematica Scientia 2013年第2期33卷 430-442页

作者： Fethi soltani Higher College of Technology and Informatics Street of the Employers 45Charguia 2 - 2035 TunisTunisia

We study the dual Dunkl-Sonine operator tSk,e on rd and give expression of tSk,t, using Dunkl multiplier operators on rd, Next, we study the extremal functions fλ, λ〉 0 related to the Dunkl multiplier operators, and more precisely show that {fλ}λ〉0 converges uniformly to tSk,e（f） as λ→0 Certain examples based on Dunkl-heat and Dunkt-Poisson kernels are provided to illustrate the results.

关键词： Dunkl transform dual Dunkl-Sonine operator multiplier operators extremalfunction

Experimental study on correlation between turbulence and sound in a subsonic wind tunnel

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Acta Mechanica Sinica 2010年第4期26卷 531-539页

作者： M.D.Manshadi K.Ghorbanian M.r.soltani Department of Aerospace Engineering Sharif University of Technology

In this paper, the effects of turbulence on sound generation and velocity fluctuations due to pressure waves in a large subsonic wind tunnel are studied. A trip strip located at different positions in the contraction part or at one position in the diffuser of a large wind tunnel is used to investigate the aforementioned phenomenon, and the results indicate that the trip strip has significant effects on sound reduction. The lowest turbulence intensity and sound are obtained from a trip strip with a diameter of 0.91 mm located either at X/L = 0.79 or at X/L = 0.115 in the wide portion of the contraction. Furthermore, the effect of monopole, dipole and quadrupole sources of aerodynamic noise at different velocities is investigated, and it is demonstrated that the contribution of the monopole is dominant, while the shares due to the dipole and quadrupole remain less important. In addition, it is found that the sound waves have a modest impact on the measured longitudinal turbulence and are generated essentially by eddies.

关键词： Wind tunnel. Turbulence Sound Quadrupole term - Correlation

Modeling and control for cooperative transport of a slung fluid container using quadrotors

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Chinese Journal of Aeronautics 2018年第2期31卷 262-272页

作者： Hassan SAYYAADI Ali soltani School of Mechanical Engineering Sharif University of Technology

In this paper, dynamic modeling and control problem for transfer of a sloshing liquid container suspended through rigid massless links from a team of quadrotors are investigated. By the proposed solution, pose of the slung container and fluid sloshing modes are stabilized appropriately. Dynamics of the container-liquid-quadrotors system is modeled by Euler-Lagrange *** slosh dynamics is included using multi-mass-spring model. According to derived model, a proper control law is designed for a system with three or more quadrotors. Implementing the proposed control law, quadrotors can control pose of the container, directions of the links and liquid sloshing modes simultaneously. Stability of closed loop system of tracking errors and sloshing modes are demonstrated using a theory of singularly perturbed systems and Lyapunov stability theorem. Also, the capability of the proposed feedback control laws in solving a formerly organized transport problem of a liquid filled container has been demonstrated in simulations. Moreover, priority of the proposed control scheme to an existing slung load controller in the literature is demonstrated.

关键词： Cooperative transport Dynamic modeling Liquid sloshing Lyapunov stability Pose control Quadrotors Slung load

SBr COMPOSITES rEINFOrCED WITH N-ISOPrOPYL-N'PHENYL-P-PHENYLENEDIAMINE-MODIFIED CLAY

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Chinese Journal of Polymer Science 2011年第2期29卷 191-196页

作者： Habibollah Baharvand Ghasem Naderi Sedigheh soltani Iran Polymer & Petrochemical Institute TehranP.O.Box 14965/115Iran

SBr compounds including the N-isopropyl-N＇-phenyl-p-phenylenediamine-modified clay（organoclay） were *** of modified clay and antioxidant（IPPD） contents on mechanical and rheological properties of SBr composites were *** results confirmed that the clay was chemically modified by IPPD and changed into an organoclay.X-ray diffraction（XrD） results confirmed the increase in interlayer distance of the clay due to the insertion of *** and cure characteristics of SBr compounds were determined using rPA（rubber Process Analyzer） and *** time and cure time of SBr compounds decreased with introduction of the *** properties and heat aging resistance of the SBr composites were improved significantly by incorporation of the organoclay.

关键词： SBr Organoclay Mechanical properties Cure characteristics Antioxidant

Tribological behavior of polydopamine/polytetrafluoroethylene coating on laser textured stainless steel with Hilbert curves

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Friction 2023年第7期11卷 1307-1319页

作者： Firuze soltani-KOrDSHULI Nathaniel HArrIS Min ZOU Department of Mechanical Engineering University of ArkansasFayetteville AR 72701USA Center for Advanced Surface Engineering University of ArkansasFayetteville AR 72701USA

Shallow Hilbert curve patterns with easily programmable texture density were selected for laser texturing of stainless steel *** different texture path segment lengths(12 and 24 μm)and four different laser power percentages(5%,10%,15%,and 20%)were *** textured and smooth substrates were coated with thin polydopamine/polytetrafluoroethylene(PDA/PTFE)coatings for tribological property *** effects of texture density(texture area coverage)and laser power on the durability and friction of the coated surfaces were *** texturing the substrates improved the coating durability up to 25 times,reduced the friction coefficient,and prevented coating global *** textures fabricated with a laser power of 15%and a texture path segment length of 12 μm yielded the best coating *** textures provided the interlocking for the PTFE coating and thus prevented its global ***,the PTFE inside the texture grooves replenished the solid lubricant worn away in the wear track and prolonged the coating wear life.

关键词： polytetrafluoroethylene(PTFE) coating durability laser texturing Hilbert curve stainless steel