Three-dimensional interactions between a finite-span synthetic jet and a crossflow

Sahni, Onkar; Wood, J. S.; Jansen, Kenneth E.; Amitay, Michael

doi:10.1017/s0022112010005604

Cited by 80 publications

(33 citation statements)

References 76 publications

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“…Along with the parameters regarding a single actuator, the control effects are also dependent on the shape of the actuator and the arrangement of the actuator array. [28][29][30] The forcing frequency of the SJ is arguably the most important parameter and is indeed the key parameter to be optimized for better separation control effect. 24,[31][32][33] Experimental and numerical results 31,34,35 reveal that the fundamental mechanism of separation control by a SJ is the formation of coherent roll-up lifting vortices not far from the airfoil surface.…”

Section: Introductionmentioning

confidence: 99%

A direct numerical simulation investigation of the synthetic jet frequency effects on separation control of low-Re flow past an airfoil

Zhang

Samtaney

2015

Physics of Fluids

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CitationA direct numerical simulation investigation of the synthetic jet frequency effects on separation control of low-Re flow past an airfoil 2015, 27 (5) We present results of direct numerical simulations of a synthetic jet (SJ) based separation control of flow past a NACA-0018 (National Advisory Committee for Aeronautics) airfoil, at 10• angle of attack and Reynolds number 10 4 based on the airfoil chord length C and uniform inflow velocity U 0 . The actuator of the SJ is modeled as a spanwise slot on the airfoil leeward surface and is placed just upstream of the leading edge separation position of the uncontrolled flow. The momentum coefficient of the SJ is chosen at a small value 2.13 × 10 −4 normalized by that of the inflow. Three forcing frequencies are chosen for the present investigation: the low frequency (LF) F + = f e C/U 0 = 0.5, the medium frequency (MF) F + = 1.0, and the high frequency (HF) F + = 4.0. We quantify the effects of forcing frequency for each case on the separation control and related vortex dynamics patterns. The simulations are performed using an energy conservative fourth-order parallel code. Numerical results reveal that the geometric variation introduced by the actuator has negligible effects on the mean flow field and the leading edge separation pattern; thus, the separation control effects are attributed to the SJ. The aerodynamic performances of the airfoil, characterized by lift and lift-to-drag ratio, are improved for all controlled cases, with the F + = 1.0 case being the optimal one. The flow in the shear layer close to the actuator is locked to the jet, while in the wake this lock-in is maintained for the MF case but suppressed by the increasing turbulent fluctuations in the LF and HF cases. The vortex evolution downstream of the actuator presents two modes depending on the frequency: the vortex fragmentation and merging mode in the LF case where the vortex formed due to the SJ breaks up into several vortices and the latter merge as convecting downstream; the discrete vortices mode in the HF case where discrete vortices form and convect downstream without any fragmentation and merging. In the MF case, the vortex dynamics is at a transition state between the two modes. The low frequency actuation has the highest momentum rate during the blowing phase and substantially affects the flow upstream of the actuator and triggers early transition to turbulence. In the LF case, the transverse velocity has a 1%U 0 pulsation at the position 18%C upstream of the actuator. C 2015 AIP Publishing LLC.

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Section: Introductionmentioning

confidence: 99%

A direct numerical simulation investigation of the synthetic jet frequency effects on separation control of low-Re flow past an airfoil

Zhang

Samtaney

2015

Physics of Fluids

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“…In addition, as the aspect ratio increased the secondary structures became less pronounced. Other works have shown how these secondary structures interact with the boundary layer and their alteration of the local flow field over unswept and swept-back finite wings (Elimelech, Vasile & Amitay 2011;Sahni et al 2011). Krishnan & Kamran (2009) conducted a study comparing different orifices at high aspect ratios with a combination of analytical modeling and hot-wire experimentation.…”

Section: Introductionmentioning

confidence: 99%

Vortex formation of a finite-span synthetic jet: effect of rectangular orifice geometry

2014

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The formation and evolution of flow structures of a finite-span synthetic jet issuing into a quiescent flow were investigated experimentally using stereoscopic particle image velocimetry (SPIV). The effect of two geometrical parameters, the orifice aspect ratio and the neck length, were explored at a Strouhal number of 0.115 and a Reynolds number of 615. Normalized orifice neck lengths of 2, 4 and 6 and aspect ratios of 6, 12, and 18 were examined. It was found that the effect of the aspect ratio is much larger than the effect of the neck length, and as the aspect ratio increases the size of the edge vortices decreases and the presence of secondary structures is more evident. Moreover, axis switching was observed and its streamwise location increases as the aspect ratio increases. The effect of the neck length on the flow structures and the evolution of the synthetic jet was found to be secondary, where the effect was only in the very near field (i.e. close to the jet's orifice).

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“…PHASTA solves the Navier-Stokes [36,37] equations either directly (DNS) or after turbulence modeling [38] using a stabilized finite element method. It has scaled to over 3M processes [39] on applications ranging from fundamental science benchmarks like channel flow [40] to more complex systems like aircraft [41,42], cardiovascular systems [43,44] and multiphase flow [45,46]. It is an open source code [47] led by K.E.…”

Section: Phasta Science Applicationmentioning

confidence: 99%

Performance Analysis, Design Considerations, and Applications of Extreme-Scale In Situ Infrastructures

Ayachit

Bauer

Duque

et al. 2016

SC16: International Conference for High Performance Computing, Networking, Storage and Analysis

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Abstract-A key trend facing extreme-scale computational science is the widening gap between computational and I/O rates, and the challenge that follows is how to best gain insight from simulation data when it is increasingly impractical to save it to persistent storage for subsequent visual exploration and analysis. One approach to this challenge is centered around the idea of in situ processing, where visualization and analysis processing is performed while data is still resident in memory. This paper examines several key design and performance issues related to the idea of in situ processing at extreme scale on modern platforms: scalability, overhead, performance measurement and analysis, comparison and contrast with a traditional post hoc approach, and interfacing with simulation codes. We illustrate these principles in practice with studies, conducted on large-scale HPC platforms, that include a miniapplication and multiple science application codes, one of which demonstrates in situ methods in use at greater than 1M-way concurrency.

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Three-dimensional interactions between a finite-span synthetic jet and a crossflow

Cited by 80 publications

References 76 publications

A direct numerical simulation investigation of the synthetic jet frequency effects on separation control of low-Re flow past an airfoil

A direct numerical simulation investigation of the synthetic jet frequency effects on separation control of low-Re flow past an airfoil

Vortex formation of a finite-span synthetic jet: effect of rectangular orifice geometry

Performance Analysis, Design Considerations, and Applications of Extreme-Scale In Situ Infrastructures

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