scholarly journals Numerical Computation and Investigation of the Characteristics of Microscale Synthetic Jets

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Ann Lee ◽  
Guan H. Yeoh ◽  
Victoria Timchenko ◽  
John Reizes
Keyword(s):  
Velocity Fields ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Moving Mesh ◽  
Experimental Result ◽  
Computational Domain ◽  
Governing Equations ◽  
Curvilinear Coordinate ◽  
Pulsating Jet ◽  
Good Agreement

A synthetic jet results from periodic oscillations of a membrane in a cavity. Jet is formed when fluid is alternately sucked into and ejected from a small cavity by the motion of membrane bounding the cavity. A novel moving mesh algorithm to simulate the formation of jet is presented. The governing equations are transformed into the curvilinear coordinate system in which the grid velocities evaluated are then fed into the computation of the flow in the cavity domain thus allowing the conservation equations of mass and momentum to be solved within the stationary computational domain. Numerical solution generated using this moving mesh approach is compared with an experimental result measuring the instantaneous velocity fields obtained by μPIV measurements in the vicinity of synthetic jet orifice 241 μm in diameter issuing into confined geometry. Comparisons between experimental and numerical results on the streamwise component of velocity profiles at the orifice exit and along the centerline of the pulsating jet in microchannel as well as the location of vortex core indicate that there is good agreement, thereby demonstrating that the moving mesh algorithm developed is valid.

Prediction of Compressible Subsonic Flow through an Axisymmetric Exhaust Valve-port Assembly

1995 ◽  
Vol 209 (4) ◽  
pp. 289-295 ◽  
Author(s):  
J A Naser ◽  
A D Gosman
Keyword(s):  
Field Data ◽  
Subsonic Flow ◽  
Numerical Procedure ◽  
Simple Algorithm ◽  
Exhaust Valve ◽  
Curvilinear Coordinate System ◽  
Governing Equations ◽  
Curvilinear Coordinate ◽  
Flow Through ◽  
Good Agreement

Flow details through an axisymmetric exhaust valve-port assembly have been investigated numerically. Computations were performed for steady compressible subsonic air flow at different valve lifts. The numerical procedure used for this purpose solves the governing equations using the SIMPLE algorithm. The governing equations are expressed in a general curvilinear coordinate system and are discretized in a finite volume fashion. The time-averaged governing equations are closed using the k–e. turbulence model. The predictions are assessed by comparing with the available experimental flow field data. Good agreement is observed between the predictions and the experiment.

Wing tip vortex control using synthetic jets

2006 ◽  
Vol 110 (1112) ◽  
pp. 673-681 ◽  
Author(s):  
P. Margaris ◽  
I. Gursul
Keyword(s):  
Synthetic Jet ◽  
Synthetic Jets ◽  
Tip Vortex ◽  
Particle Image Velocimetry System ◽  
Driving Frequency ◽  
Velocity Measurements ◽  
Vortex Control ◽  
Image Velocimetry ◽  
Wing Tip ◽  
Jet Blowing

AbstractAn experimental investigation was conducted to study the effect of synthetic jet (oscillatory, zero net mass flow jet) blowing near the wing tip, as a means of diffusing the trailing vortex. Velocity measurements were taken, using a Particle Image Velocimetry system, around the tip and in the near wake of a rectangular wing, which was equipped with several blowing slots. The effect of the synthetic jet was compared to that of a continuous jet blowing from the same configurations. The results show that the use of synthetic jet blowing is generally beneficial in diffusing the trailing vortex and comparable to the use of continuous jet. The effect was more pronounced for the highest blowing coefficient used. The driving frequency of the jet did not generally prove to be a significant parameter. Finally, the instantaneous and the phase-locked velocity measurements helped explain the different mechanisms employed by the continuous and synthetic jets in diffusing the trailing vortex.

Micro Fluidic Jets for Thermal Management of Electronics

Volume 4 ◽  
2004 ◽  
Author(s):  
Jivtesh Garg ◽  
Mehmet Arik ◽  
Stanton Weaver ◽  
Seyed Saddoughi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heated Surface ◽  
Turbulent Jets ◽  
Harmonic Signal ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Small Scale ◽  
Air Cooling ◽  
Infrared Thermal Imaging

Micro fluidics devices are conventionally used for boundary layer control in many aerospace applications. Synthetic Jets are intense small scale turbulent jets formed from entrainment and expulsion of the fluid in which they are embedded. The idea of using synthetic jets in confined electronic cooling applications started in late 1990s. These micro fluidic devices offer very efficient, high magnitude direct air-cooling on the heated surface. A proprietary synthetic jet designed in General Electric Company was able to provide a maximum air velocity of 90 m/s from a 1.2 mm hydraulic diameter rectangular orifice. An experimental study for determining the thermal performance of a meso scale synthetic jet was carried out. The synthetic jets are driven by a time harmonic signal. During the experiments, the operating frequency for jets was set between 3 and 4.5 kHz. The resonance frequency for a particular jet was determined through the effect on the exit velocity magnitude. An infrared thermal imaging technique was used to acquire fine scale temperature measurements. A square heater with a surface area of 156 mm2 was used to mimic the hot component and extensive temperature maps were obtained. The parameters varied during the experiments were jet location, driving jet voltage, driving jet frequency and heater power. The output parameters were point wise temperatures (pixel size = 30 μm), and heat transfer enhancement over natural convection. A maximum of approximately 8 times enhancement over natural convection heat transfer was measured. The maximum coefficient of cooling performance obtained was approximately 6.6 due to the low power consumption of the synthetic jets.

Study on Surface Roughness Muring Metal Manufacturing Process

2011 ◽  
Vol 325 ◽  
pp. 731-736
Author(s):  
Zheng Yi Jiang ◽  
Shu Jun Wang ◽  
Dong Bin Wei ◽  
Hei Jie Li ◽  
Hai Bo Xie ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Crack Nucleation ◽  
Metal Plate ◽  
Experimental Result ◽  
Strip Rolling ◽  
Surface Asperity ◽  
Asperity Flattening ◽  
Cold Strip Rolling ◽  
Effect Of Surface ◽  
Good Agreement

In the paper, a crystal plasticity finite element method (CPFEM) model was developed based on ABAQUS to analyse the surface roughness transfer during metal manufacturing. The simulation result shows a good agreement with the experimental result in the flattening of surface asperity, and the surface roughness decreases significantly with an increase of reduction with considering friction effect. Lubrication can delay surface asperity flattening. The effect of surface roughness on produced metal defect (crack) was also studied, and the surface roughness affects the crack initiation significantly in cold strip rolling. In addition, the surface roughness variation along the metal plate width contributes to stress distribution and then inhibition of crack nucleation.

Numerical Investigation of a Fiber Web Effect on the Pressure Drop and Particles Collection in a Microchannel

2009 ◽  
Author(s):  
Alireza Dastan ◽  
Omid Abouali
Keyword(s):  
Pressure Drop ◽  
Flow Field ◽  
Numerical Investigation ◽  
Particle Motion ◽  
Particle Deposition ◽  
Hydraulic Diameter ◽  
Lagrangian Approach ◽  
Computational Domain ◽  
Governing Equations ◽  
Eulerian Approach

In this paper pressure drop and particle deposition in a microchannel with a hydraulic diameter of 225 micrometer is investigated numerically. Several hundred micron length fibers caught at the entrance of the channels making a “fiber web” also is modeled in this research. Governing equations for the flow field are solved with an Eulerian approach while the equations of particle motion in the flow are solved by a Lagrangian approach. Assuming the symmetry in the domain, one channel and the corresponding plenum are studied in the computational domain. For studying the effects of fibers in the flow, two fiber webs with four and six solid fibers are studied. The increase of pressure drop in the microchannel because of the entrance fiber web is computed and discussed. Also deposition and collection of the particles with various diameters at the fiber webs are also presented.

Optimization of synthetic jet actuation by analytical modeling

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Max Huber ◽  
Andreas Zienert ◽  
Perez Weigel ◽  
Martin Schüller ◽  
Hans-Reinhard Berger ◽  
...  
Keyword(s):  
High Performance ◽  
Synthetic Jet ◽  
Parameter Study ◽  
Content Type ◽  
One Dimensional ◽  
Wide Range ◽  
Jet Actuators ◽  
Different Dimensions ◽  
Oscillation Correction ◽  
Good Agreement

Purpose The purpose of this paper is to analyze and optimize synthetic jet actuators (SJAs) by means of a literature-known one-dimensional analytical model. Design/methodology/approach The model was fit to a wide range of experimental data from in-house built SJAs with different dimensions. A comprehensive parameter study was performed to identify coupling between parameters of the model and to find optimal dimensions of SJAs. Findings The coupling of two important parameters, the diaphragm resonance frequency and the cavity volume, can be described by a power law. Optimal orifice length and diameter can be calculated from cavity height in good agreement with literature. A transient oscillation correction is required to get correct simulation outcomes. Originality/value Based on these findings, SJA devices can be optimized for maximum jet velocity and, therefore, high performance.

THE EFFECTS OF HALL CURRENT ON THE FLOW DUE TO THE OSCILLATING ROTATING POROUS DISK WITH A VISCOUS FLUID AT INFINITY: GRAPHICAL SOLUTIONS USING MATLAB

2021 ◽  
Vol 10 (5) ◽  
pp. 2491-2511
Author(s):  
R. Lakshmi ◽  
A. Santhakumari
Keyword(s):  
Viscous Fluid ◽  
Closed Form ◽  
Hall Current ◽  
Velocity Fields ◽  
Governing Equations ◽  
Porous Disk ◽  
Suction And Blowing

The flow due to the oscillating rotating porous disk with a viscous fluid at infinity is studied under the influence of Hall current. Governing equations are implied with reasonable approximations and solved analytically to get the expressions for the velocity fields in closed form. Graphical results are presented for the velocity components for various values of parameters namely, the Hall, suction and blowing through MATLAB and a discussion is provided. It is important to note that presented results are valid for all values of the frequencies.

Experimental Investigation of the Effect of Synthetic Jets in Minichannels With Subcooled Boiling Flow

2013 ◽  
Author(s):  
David M. Sykes ◽  
Andrew L. Carpenter ◽  
Gregory S. Cole
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Heat Transfer ◽  
Local Heat ◽  
High Heat ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Augmentation

Microchannels and minichannels have been shown to have many potential applications for cooling high-heat-flux electronics over the past 3 decades. Synthetic jets can enhance minichannel performance by adding net momentum flux into a stream without adding mass flux. These jets are produced because of different flow patterns that emerge during the induction and expulsion stroke of a diaphragm, and when incorporated into minichannels can disrupt boundary layers and impinge on the far wall, leading to high heat transfer coefficients. Many researchers have examined the effects of synthetic jets in microchannels and minichannels with single-phase flows. The use of synthetic jets has been shown to augment local heat transfer coefficients by 2–3 times the value of steady flow conditions. In this investigation, local heat transfer coefficients and pressure loss in various operating regimes were experimentally measured. Experiments were conducted with a minichannel array containing embedded thermocouples to directly measure local wall temperatures. The experimental range extends from transitional to turbulent flows. Local wall temperature measurements indicate that increases of heat transfer coefficient of over 20% can occur directly below the synthetic jet with low exit qualities. In this study, the heat transfer augmentation by using synthetic jets was dictated by the momentum ratio of the synthetic jet to the bulk fluid flow. As local quality was increased, the heat transfer augmentation dropped from 23% to 10%. Surface tension variations had a large effect on the Nusselt number, while variations in inertial forces had a small effect on Nusselt number in this operating region.

Numerical Investigation of Blade Flutter at or Near Stall in Axial Flow Turbomachines

2001 ◽  
Author(s):  
Wolfgang Höhn
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Separated Flow ◽  
Parallel Computer ◽  
Navier Stokes ◽  
Computational Domain ◽  
Compressor Cascade ◽  
Governing Equations ◽  
Navier Stokes Equations ◽  
Blade Flutter

During the design of the compressor and turbine stages of today’s aeroengines, aerodynamically induced vibrations become increasingly important since higher blade load and better efficiency are desired. In this paper the development of a method based on the unsteady, compressible Navier-Stokes equations in two dimensions is described in order to study the physics of flutter for unsteady viscous flow around cascaded vibrating blades at stall. The governing equations are solved by a finite difference technique in boundary fitted coordinates. The numerical scheme uses the Advection Upstream Splitting Method to discretize the convective terms and central differences discretizing the viscous terms of the fully non-linear Navier-Stokes equations on a moving H-type mesh. The unsteady governing equations are explicitly and implicitly marched in time in a time-accurate way using a four stage Runge-Kutta scheme on a parallel computer or an implicit scheme of the Beam-Warming type on a single processor. Turbulence is modelled using the Baldwin-Lomax turbulence model. The blade flutter phenomenon is simulated by imposing a harmonic motion on the blade, which consists of harmonic body translation in two directions and a rotation, allowing an interblade phase angle between neighboring blades. Non-reflecting boundary conditions are used for the unsteady analysis at inlet and outlet of the computational domain. The computations are performed on multiple blade passages in order to account for nonlinear effects. A subsonic massively stalled unsteady flow case in a compressor cascade is studied. The results, compared with experiments and the predictions of other researchers, show reasonable agreement for inviscid and viscous flow cases for the investigated flow situations with respect to the Steady and unsteady pressure distribution on the blade in separated flow areas as well as the aeroelastic damping. The results show the applicability of the scheme for stalled flow around cascaded blades. As expected the viscous and inviscid computations show different results in regions where viscous effects are important, i.e. in separated flow areas. In particular, different predictions for inviscid and viscous flow for the aerodynamic damping for the investigated flow cases are found.

Numerical and Experimental Evaluation of Turbulent Flow in Volute

2003 ◽  
Author(s):  
Akitomo Igarashi ◽  
Kazuyuki Toda ◽  
Makoto Yamamoto ◽  
Toshimichi Sakai
Keyword(s):  
Numerical Simulation ◽  
Cross Section ◽  
Three Dimensional ◽  
Experimental Result ◽  
Centrifugal Fan ◽  
Flow Conditions ◽  
Flow Angle ◽  
Fan Performance ◽  
Centrifugal Fans ◽  
Good Agreement

The performance of centrifugal fans is considerably influenced by the design of tongue at the re-circulation port. The flow in the volute of a centrifugal fan was studied both experimentally and numerically. In this experiment, flow angle, pressure and velocity profiles were measured at a large number of locations in the volute. The flow field in the volute passage was analyzed using Computational Fluid Dynamics. The flow was assumed to be three dimensional, turbulent and steady. The numerical simulation produced qualitatively good agreement with the experimental result. The results from experiment and numerical simulation indicated that the adoption of a re-circulating flow port improved fan performance for all flow conditions. In addition, the existence of strong secondary flow was apparent at the cross-section of the volute passage.

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