Effects of Zero-Mass “Synthetic” Jets on the Aerodynamics of the NACA-0012 Airfoil

Hassan, Ahmed A.; Janakiram, Ram D.

doi:10.4050/jahs.43.303

Cited by 37 publications

(10 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A few such attempts [5,13,33,37] have demonstrated qualitatively agreement with experiments. However, direct solving the unsteady RANS equations requires resolving the different scales associated with the base flow and the perturbation.…”

Section: Introductionmentioning

confidence: 65%

On the Interaction of Turbulent Shear Layers with Harmonic Perturbations

Lifshitz

Degani

Tumin

2007

Flow Turbulence Combust

View full text Add to dashboard Cite

The problem of coherent perturbations in a turbulent shear layer is considered for the purpose of developing a mathematical model based on a triple decomposition that extracts the coherent components of random fluctuations. The governing equations for the mean and the coherent parts of flow are derived, assuming the eddy-viscosity equivalence for the random part of flow, and solved by iterations to provide a coupled solution of the problem as a whole. Calculations agree well with experimental data in the upstream part of the layer where the mean-coherent flow interaction is the most important. In this region, the interaction changes the mean flow velocity distribution in such a manner that the neutral stability curve is shifted upstream relative to its position in the undisturbed layer and the perturbation intensity decreases further downstream. Experiments show that the coherent waves suppress the turbulent Reynolds stress production downstream of this region, but the model fails to predict the layer spreading correctly probably due to an inadequate turbulence closure of the mean flow. For the case of a turbulent mixing layer, we suggest a new closure relation that takes into account this coherent-random interaction.

show abstract

Section: Introductionmentioning

confidence: 65%

On the Interaction of Turbulent Shear Layers with Harmonic Perturbations

Lifshitz

Degani

Tumin

2007

Flow Turbulence Combust

View full text Add to dashboard Cite

show abstract

“…As long as Large Eddy Simulation will remain too expensive for overnight simulations, some room exists for the development of less expensive methods able to predict the very large scales of the flow. This type of approaches has important applications in different domains: among others, aeronautics (Gatski, 2001;Jin and Braza, 1994), control (Getin, 2000;Hassan and Janakiram, 1997), aeroacoustics (Bastin et al, 1997), power generation (Benhamadouche and Laurence, 2003) and environment (Kenjereš et al, 2005(Kenjereš et al, , 2001 can be cited.…”

Section: Introductionmentioning

confidence: 99%

Turbulence modelling of statistically periodic flows: Synthetic jet into quiescent air

Carpy

Manceau

2006

International Journal of Heat and Fluid Flow

View full text Add to dashboard Cite

Computations of a 2D synthetic jet are performed with usual RANS equations solved in time-accurate mode (URANS), with the standard k-e model and the Rotta + IP second moment closure. The purpose of the present work is to investigate the ability of these standard turbulence models to close the phase-averaged Navier-Stokes equations. Results are compared with recent experiments by Yao et al. made available to the CFD Validation of Synthetic Jets and Turbulent Separation Control workshop held in Williamsburg in 2004. Comparisons of the performance of the models with experimental data show that the evolution of the vortex dipole generated by inviscid mechanisms is not correctly reproduced by the k-e model. The Reynolds-stress model gives much more realistic predictions. However, several characteristics are not well predicted, as for instance the convection velocity. A detailed analysis shows that the vortex dipole dynamics is essentially inviscid during the early blowing phase, when the flow is more transitional than fully turbulent. Turbulence develops and influences the dynamics of the vortices only at a later stage of the blowing phase. Consequently, it is of importance that the turbulence models do not predict erroneously high levels of turbulence. In particular, the present study shows that the correct prediction of the region of negative production that appears during the deceleration of the blowing velocity, due to the misalignment of the strain and anisotropy tensors, is crucial. Therefore, linear eddy-viscosity models must be discarded for this type of pulsed flows, in particular for flow control using synthetic jets.

show abstract

“…This reduces the volume of the cavity, thereby raising the pressure, which then drives a jet through the exit orifice into the boundary layer. If an oscillating electric field is applied to the driver the diaphragm oscillates up and down thereby producing a synthetic jet [1][2][3][4][5][6][7][8][9][10][11][12][13][14]18]. Alternatively if a unidirectional electric field is applied the diaphragm only deflects upwards to produce a kind of pulse jet [15][16][17]; we will follow [16] and call this mode of operation a pressurejump actuator.…”

Section: Introductionmentioning

confidence: 99%

“…A popular generic model of many micro-jet actuators currently being studied for flow-control applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] is depicted in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

Is Helmholtz Resonance a Problem for Micro-jet Actuators?

Lockerby

Carpenter

Davies

2007

Flow Turbulence Combust

View full text Add to dashboard Cite

A theoretical analysis is described that determines the conditions for Helmholtz resonance for a popular class of self-contained microjet actuator used in both synthetic-and pressure-jump (pulse-jet) mode. It was previously shown that the conditions for Helmholtz resonance are identical to those for optimizing actuator performance for maximum mass flux. The methodology is described for numerical-simulation studies on how Helmholtz resonance affects the interaction of active and nominally inactive micro-jet actuators with a laminar boundary layer. Two sets of numerical simulations were carried out. The first set models the interaction of an active actuator with the boundary layer. These simulations confirm that our criterion for Helmholtz resonance is broadly correct. When it is satisfied we find that the actuator cannot be treated as a predetermined wall boundary condition because the interaction with the boundary layer changes the pressure difference across the exit orifice thereby affecting the outflow from the actuator. We further show that strong inflow cannot be avoided even when the actuator is used in pressurejump mode. In the second set of simulations two-dimensional Tollmien-Schlichting waves, with frequency comparable with, but not particularly close to, the Helmholtz resonant frequency, are incident on a nominally inactive micro-jet actuator. The simulations show that under these circumstances the actuators act as strong sources of 3D Tollmien-Schlichting waves. It is surmised that in the real-life aeronautical applications with turbulent boundary layers broadband disturbances of the pressure field, including acoustic waves, would cause nominally inactive actuators, possibly including pulsed jets, to act as strong disturbance sources. Should this be true it Flow Turbulence Combust (2007) 78:205-222 would probably be disastrous for engineering applications of such massless microjet actuators for flow control.

show abstract

Effects of Zero-Mass “Synthetic” Jets on the Aerodynamics of the NACA-0012 Airfoil

Cited by 37 publications

References 6 publications

On the Interaction of Turbulent Shear Layers with Harmonic Perturbations

On the Interaction of Turbulent Shear Layers with Harmonic Perturbations

Turbulence modelling of statistically periodic flows: Synthetic jet into quiescent air

Is Helmholtz Resonance a Problem for Micro-jet Actuators?

Contact Info

Product

Resources

About