Low Frequency Piezoelectric Synthetic Jets

2010 ◽  
Author(s):  
Charles E. Seeley ◽  
Mehmet Arik ◽  
Yogen Uttukar ◽  
Tunc Icoz
Keyword(s):  
Low Cost ◽  
Heated Surface ◽  
Fluid Structure Interaction ◽  
Low Frequency ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Active Cooling ◽  
Compact Size

Active cooling is often required for circuit boards with high heat generation densities. Synthetic jets driven with piezoelectric actuators offer interesting capabilities for localized active cooling of electronics due to their compact size, low cost and substantial cooling effectiveness. The design of synthetic jets for specific applications requires practical design tools that capture the strong fluid structure interaction without long run times. There is particular interest in synthetic jets that have a low operating frequency to reduce noise levels. This paper describes how common finite element (FE) and computational fluid dynamics (CFD) codes can be used to calculate parameters for a synthetic jet fluid structure interaction (FSI) model that only requires a limited number of degrees of freedom and is solved using a direct approach for low frequency synthetic jets. Tests are performed based on impinging on a heated surface to measure heat transfer enhancement. The test results are compared to the FSI model results for validation and agreement is found to be good in the frequency range of interest from 200 to 500 Hz.

Fluid-Structure Interaction Model of a Synthetic Jet Using Coupled Computational Fluid Dynamics and Finite Elements

2012 ◽  
Author(s):  
Charles E. Seeley ◽  
Stan Weaver ◽  
Brian Rush
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Structure Interaction ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Working Fluid ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Active Cooling ◽  
Compact Size

Synthetic jets offer new capabilities for localized active cooling of electronics due to their compact size, low cost and substantial cooling effectiveness. The design of devices to create synthetic jets and optimize active cooling performance is challenging due to the strong, two way, fluid-structure interaction (FSI) between the working fluid and the flexible structure that moves the fluid driven with piezoelectric actuators. Previous modeling efforts relied on lumped parameter approaches or electrical analogs. Although computationally less intensive, these approaches may not be accurate in all regions of the design space of interest and trade off fidelity for ease of use. In this effort, a 3D finite element model of the structure is coupled with a 3D computational fluid dynamics model of the fluid to explore the viability of such an approach. The motion of the structure moves the fluid grid, and the fluid feeds back pressure forces onto the structure that are required to converge at each iteration. Transient response of the deflection, pressure and exit velocity will be presented. Validation of the FSI model with experimental data for the frequency response of these quantities will also be presented.

Fluid-Structure Interaction Model for Low-Frequency Synthetic Jets

AIAA Journal ◽  
2011 ◽  
Vol 49 (2) ◽  
pp. 316-323 ◽  
Author(s):  
Charles E. Seeley ◽  
Yogen Utturkar ◽  
Mehmet Arik ◽  
Tunc Icoz
Keyword(s):  
Fluid Structure Interaction ◽  
Low Frequency ◽  
Interaction Model ◽  
Synthetic Jets ◽  
Fluid Structure ◽  
Structure Interaction

A Perturbation Method for Low-Frequency Fluid-Structure Interaction Problems

1973 ◽  
Vol 40 (2) ◽  
pp. 388-394 ◽  
Author(s):  
Y. K. Lou
Keyword(s):  
Wave Equation ◽  
Perturbation Method ◽  
Electromagnetic Scattering ◽  
Perturbation Methods ◽  
Separation Of Variables ◽  
Fluid Structure Interaction ◽  
Low Frequency ◽  
Approximate Solutions ◽  
Fluid Structure ◽  
Structure Interaction

Perturbation methods have been used for electromagnetic scattering and diffraction problems in recent years. A similar method suitable for low-frequency fluid-structure interaction problems is presented. The essence of the method lies in the fact that approximate solutions for fluid-structure interaction problems can be obtained from a set of Poisson’s equations, rather than from the reduced wave equation. The method is particularly useful for those problems where the Poisson’s equation may be solved by the method of separation of variables while the reduced wave equation cannot. As an illustrative example, the vibrations of a submerged spherical shell is studied using the perturbation method and the accuracy of the method is demonstrated.

Electronic Cooling Using Synthetic Jets

2005 ◽  
Author(s):  
Anna A. Pavlova ◽  
Michael Amitay
Keyword(s):  
Reynolds Number ◽  
Heated Surface ◽  
Low Frequency ◽  
Heat Removal ◽  
Jet Impingement ◽  
Constant Heat Flux ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Impingement Cooling ◽  
Jet Cooling

Efficiency of synthetic jet impingement cooling and the mechanisms of heat removal from a constant heat flux surface were investigated experimentally. The effects of jet’s formation frequency and Reynolds number at different nozzle-to-surface distances were investigated and compared to steady jet cooling. It was found that synthetic jets are up to three times more effective than steady jets at the same Reynolds number. For smaller distances, high formation frequency (f = 1200 Hz) synthetic jets remove heat better than low frequency (f = 420 Hz) jets, whereas low frequency jets are more effective at larger distances, with an overlapping region. Using PIV, it was shown that at small distances between the synthetic jet and the heated surface, the higher formation frequency jet is associated with accumulation of vortices before they impinge on the surface. For the lower frequency jet, the wavelength between coherent structures is so large that vortex rings impinge on the surface separately.

Study of a Fluid-Structure Interaction Instability Mechanism in a Tube Bundle With Multiphase-POD Approach

2013 ◽  
Author(s):  
Marie Pomarède ◽  
Erwan Liberge ◽  
Jean-François Sigrist ◽  
Aziz Hamdouni ◽  
Elisabeth Longatte
Keyword(s):  
Tube Bundle ◽  
Low Cost ◽  
Fluid Structure Interaction ◽  
Computational Cost ◽  
Order Method ◽  
Instability Mechanism ◽  
Cost Study ◽  
Fluid Structure ◽  
Reduced Order ◽  
Structure Interaction

Multiphase-Proper Orthogonal Decomposition Reduced-Order Method has been proven to be efficient for the low-cost study of fluid-structure interaction mechanisms. Applications to a single tube under cross-flow, then to a tube bundle system revealed good behaviours of this method, which was shown to be able to accurately reproduce the velocity flow field as well as the solid displacement, even in the case of large magnitudes. The goal here is to go further by studying an instability mechanism with the Multiphase-POD technique, involving a tube array configuration because of its high interest in the nuclear domain. We first want to know if this method can reproduce critical to unstable cases and finally, we are interested in the possibility of leading a parametric study coupled with the Multiphase-POD Method in order to evaluate the instability threshold. Indeed, parametric studies coupled with a reduced-order method could lead to a CPU time additional gain, since only one basis calculation could cover several configurations with low computational cost.

Modal Analysis of a Nuclear Reactor With Fluid-Structure Interaction: Influence of Fluid Compressibility

2006 ◽  
Author(s):  
Jean-Franc¸ois Sigrist ◽  
Daniel Broc
Keyword(s):  
Modal Analysis ◽  
Compressible Fluid ◽  
Nuclear Reactor ◽  
Fluid Structure Interaction ◽  
Low Frequency ◽  
Operating Pressure ◽  
Fluid Structure ◽  
Displacement Potential ◽  
Structure Interaction ◽  
Temperature Conditions

The present paper deals with the modal analysis of a nuclear with fluid-structure interaction effects. In a previous study, added mass and added stiffness effects due to fluid-structure interaction were modeled and studied. A dynamic analysis was performed for a seismic excitation, i.e. in the low frequency range. The present study deals with high frequency analysis, i.e. taking into account compressibility effects in the fluid problem. Elasto-acoustic coupling phenomena are studied and described in the industrial case. The elasto-acoustic coupled problem is formulated using the displacement/pressure-displacement potential coupled formulation which yields symmetric matrices. A modal analysis is first performed on the fluid problem alone, with a calculation of acoustic eigenfrequencies and the corresponding modal masses. A modal analysis is then performed for the coupled fluid-structure problem in the case of an incompressible fluid and a compressible fluid at standard pressure and temperature conditions and for a compressible fluid at the operating pressure and temperature conditions. Elasto-coupling effects are then highlighted and discussed.

scholarly journals Experimental Characterization of High-Amplitude Fluid–Structure Interaction of a Flexible Hydrofoil at High Reynolds Number

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Brian R. Elbing ◽  
Steven D. Young ◽  
Michael L. Jonson ◽  
Robert L. Campbell ◽  
Brent A. Craven ◽  
...  
Keyword(s):  
Initial Conditions ◽  
Model Development ◽  
Fluid Structure Interaction ◽  
Low Frequency ◽  
High Amplitude ◽  
Cylinder Wake ◽  
Constraint Forces ◽  
Fluid Structure ◽  
Structure Interaction ◽  
High Reynolds

Abstract A fluid–structure interaction (FSI) experiment was performed to study low-frequency (∼10 Hz), high-amplitude (±3.5% of the span) fin motion. This was achieved by placing an Inconel swept-fin at −9.6 deg angle-of-attack within the wake of a roughened cylinder. Speeds between 2.5 and 3.6 m/s produced cylinder diameter-based Reynolds numbers between 190,000 and 280,000, respectively. Detailed descriptions of the geometry, material/structural behavior, fluid properties, and initial conditions are provided to facilitate computational model development. Given the initial conditions, the resulting forced fin behavior was characterized with measurements of the mean and fluctuating velocity upstream of the fin (i.e., within the cylinder wake), fin tip/surface motion, and fin constraint forces/moments. This work provides a detailed experimental dataset of conditions mimicking a crashback event that is also a challenging FSI benchmark problem involving turbulent, vortex-induced structure motion. It has been used as a validation condition for FSI simulations, and it can be used to validate other FSI models as well as identifying strengths and weaknesses of various modeling approaches.

scholarly journals Effects of Frequency and Jet to Surface Spacing on Synthetic Jet Impingement Heat Transfer

2020 ◽  
Vol 9 (5) ◽  
pp. 655-660
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heated Surface ◽  
Low Frequency ◽  
Jet Impingement ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Nozzle Geometry ◽  
Ansys Fluent ◽  
Piston Cylinder

Synthetic jet is a new technique for electronic chip cooling, which combines stagnant air to form a jet resulting from periodic diaphragm oscillations in a cavity. In this work, the heat transfer characteristics of a synthetic jet are investigated experimentally and numerically. A Piston-cylinder arrangement powers the synthetic jet through a circular orifice for the impingement of jet on the heated surface. Air is considered as the cooling medium. The major parameters identified to describe the impinging jet heat transfer are Reynolds number, frequency, ratio of jet spacing to diameter(Z/D) and nozzle geometry. Numerical studies have been carried out using the finite volume based commercial software ANSYS Fluent. The turbulent model used is k-ω model. The dimensionless distance between the nozzle and plate surface is in the range 2 to 16. Numerical results are in fair agreement with experimental results. As the frequency increases the average Nusselt number increases. High frequency synthetic jets were found to remove more heat than low frequency jets for small Z/D ratio, while low frequency jets are more effective at larger Z/D ratio. Nusselt number is maximum at the stagnation point and there occurs a secondary peak at lower Z/D ratios. Synthetic jet with rectangular orifice is more effective as compared to circular and square geometries.

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