Sensitivity of synthetic jets to the design of the jet cavity

Utturkar, Yogen; Mittal, Rajat; Rampunggoon, P.; Cattafesta, Louis N.

doi:10.2514/6.2002-124

Cited by 71 publications

(30 citation statements)

References 11 publications

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“…A cavity with a very large separation between the opening and the back of the cavity may never experience impingement, whereas SJAs with very shallow cavities have been observed to generate arrays of counter-rotating vortices within Pressure and work of deformable jet producing cavity bodies the cavity, especially when a crossflow is present (Utturkar et al 2002). Unlike the previous three subsections, where the other sources of vorticity are modelled for any general cavity body, this section will focus on modelling circulation from vortex ring impingement for the particular case where the back cavity surface has a curvature which is small compared to the opening diameter, and where separation, h, is small enough to facilitate impingement, similar to the experimental actuator.…”

Section: Vortex Ring Impingement and Boundary Layer Formationmentioning

confidence: 98%

Pressure and work analysis of unsteady, deformable, axisymmetric, jet producing cavity bodies

Krieg

Mohseni

2015

J. Fluid Mech.

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This work lays out a methodology for calculating the pressure distribution internal to a generic, deformable, axisymmetric body with an internal cavity region whose deformation expels/ingests finite jets of water. This work is partially motivated by a desire to model instantaneous jetting forces and total work required for jellyfish and cephalopod locomotion, both of which can be calculated from the internal pressure distribution. But the derivation is non-specific and can be applied to any axisymmetric, deformable body (organic or synthetic) driving fluid in or out of an internal cavity. The pressure distribution over the inner surface is derived by integrating the momentum equation along a strategic path, equating local surface pressure to known quantities such as stagnation pressure, and correlating unknown terms to the total circulation of characteristic regions. The integration path is laid out to take advantage of symmetry conditions, inherent irrotationality, and prescribed boundary conditions. The usefulness/novelty of this approach lies in the fact that circulation is an invariant of motion for inviscid flows, allowing it to be modelled by a series of vorticity flux and source terms. In this study we also categorize the various sources of circulation in the general cavity-jet system, providing modelling for each of these terms with respect to known cavity deformation parameters. Through this approach we are able to isolate the effect of different deformation behaviours on each of these circulation components, and hence on the internal pressure distribution. A highly adaptable, transparent, prototype jet actuator was designed and tested to measure the circulation in the cavity and the surrounding fluid as well as the dynamic forces acting on the device during operation. The circulation in both the jet and cavity regions shows good agreement with the inviscid modelling, except at the end of the refill phase where circulation is lost to viscous dissipation. The total instantaneous forces produced during actuation are accurately modelled by the pressure analysis during both expulsion and refilling phases of the jetting cycle for multiple deformation programs. Independent of the end goal, such as propulsion, mixing, feeding etc., the efficiency of the process will always be inversely proportional to the total energy required to drive the system. Therefore, given a consistent output, efficiency is maximized by the minimum required energy. Here it is observed (somewhat 338 M. Krieg and K. Mohseni counter-intuitively) that, for both jetting and refilling, total work required to drive the fluid is lower for impulsive velocity programs with fast accelerations at the start and end of motion than sinusoidal velocity programs with smoother gradual accelerations. The underlying cause is that sinusoidal programs result in a peak in pressure (force) simultaneously with maximum deflection velocity of the deformable boundary driving fluid motion; for the impulsive programs these peaks are out of phase and overall energy c...

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Section: Vortex Ring Impingement and Boundary Layer Formationmentioning

confidence: 98%

Pressure and work analysis of unsteady, deformable, axisymmetric, jet producing cavity bodies

Krieg

Mohseni

2015

J. Fluid Mech.

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“…It has been previously shown that the behavior of the flowfield emanating from the slot is primarily sensitive to the cavity volume and not its shape. 23 The oscillatory diaphragm properties include the angular frequency of oscillation ω, its fundamental resonant frequency ω d , and the volume displaced by it ∀, whereas the relevant fluid properties are the isentropic speed of sound c 0 and the kinematic viscosity ν. These 11 parameters contain the two primary dimensions of length and time; thus, there are 9 dimensionless parameters.…”

Section: Vortex-based Jet Formation Criterionmentioning

confidence: 99%

Formation Criterion for Synthetic Jets

et al. 2005

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A formation criterion for synthetic jets is proposed and validated. A synthetic jet actuator is a zero-net mass-flux device that imparts momentum to its surroundings. Jet formation is defined as the appearance of a time-averaged outward velocity along the jet axis and corresponds to the generation and subsequent convection or escape of a vortex ring. It is shown that over a wide range of operating conditions synthetic jet formation is governed by the jet Strouhal number Sr (or Reynolds number Re and Stokes number S). Both numerical simulations and experiments are performed to supplement available two-dimensional and axisymmetric synthetic jet formation data in the literature. The data support the jet formation criterion 1/Sr = Re/S 2 > K, where the constant K is approximately 1 and 0.16 for two-dimensional and axisymmetric synthetic jets, respectively. In addition, the dependence of the constant K on the normalized radius of curvature of a rounded orifice or slot is addressed. The criterion is expected to serve as a useful design guide for synthetic jet formation in flow control, heat transfer, and acoustic liner applications, in which a stronger jet is synonymous with increased momentum transfer, vorticity generation, and acoustic nonlinearities.

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“…One such method consists of applying, a typically macro scale concept, the synthetic jet. Synthetic jets (Glezer and Amitay, 2002;Mittal et al, 2001;Mittal and Rampunggoon, 2002;Utturkar et al, 2002) have proven to be a useful meso and micro fluid device with applications including thrust vectoring, mixing enhancement, control of boundary layer separation and turbulence control. Synthetic jets are formed from alternating suction and ejection of fluid across an orifice with zero net mass flux.…”

Section: Introductionmentioning

confidence: 99%

Application of the synthetic jet concept to low Reynolds number biosensor microfluidic flows for enhanced mixing: a numerical study using the lattice Boltzmann method

Mautner

2004

Biosensors and Bioelectronics

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Sensitivity of synthetic jets to the design of the jet cavity

Cited by 71 publications

References 11 publications

Pressure and work analysis of unsteady, deformable, axisymmetric, jet producing cavity bodies

Pressure and work analysis of unsteady, deformable, axisymmetric, jet producing cavity bodies

Formation Criterion for Synthetic Jets

Application of the synthetic jet concept to low Reynolds number biosensor microfluidic flows for enhanced mixing: a numerical study using the lattice Boltzmann method

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