Three Dimensional RANS Computation Using Deforming Mesh for Synthetic Jet Simulation

2011 ◽  
Author(s):  
Ilyong Yoo ◽  
Seungsoo Lee
Keyword(s):  
Three Dimensional ◽  
Synthetic Jet ◽  
Deforming Mesh

scholarly journals Effect of orifice shape on three-dimensional vortex structure of a synthetic jet

2015 ◽  
Vol 81 (831) ◽  
pp. 15-00301-15-00301
Author(s):  
Hiroaki HASEGAWA ◽  
Tetsuya MIYAKOSHI
Keyword(s):  
Vortex Structure ◽  
Three Dimensional ◽  
Synthetic Jet

Three-Dimensional Modelling of Heat Transfer in Micro-Channels With Synthetic Jet

2010 ◽  
Author(s):  
Ann Lee ◽  
Victoria Timchenko ◽  
Guan H. Yeoh ◽  
John A. Reizes
Keyword(s):  
Heat Transfer ◽  
Silicon Substrate ◽  
Three Dimensional ◽  
Synthetic Jet ◽  
Numerical Results ◽  
Maximum Temperature ◽  
Complex Conjugate ◽  
Two Dimensional ◽  
Flow And Heat Transfer ◽  
Micro Channels

An in-house computer code is developed and applied to investigate the effect of a synthetic jet on heat transfer rates in forced convection of water in silicon micro-channels etched in the rear side of the silicon substrate. To account for the deflection of the membrane located at the bottom of the actuator cavity, a moving mesh technique to solve the flow and heat transfer is purposefully adopted. 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, momentum and energy to be solved within the stationary computational domain. The fully three-dimensional model considers the SIMPLE method to link the pressure and velocity. A heat flux of 1 MW/m2 is applied at the surface of the top of the silicon wafer and the resulting complex, conjugate heat transfer through the silicon substrate is included. The hydrodynamics feature of the flow is validated against existing experimental results and verified against numerical results from commercial package ANSYS CFX 11.0. Good agreement has been achieved. To track the development of the flow and heat transfer when the actuator is switched on, numerical results of 20 full cycles of the actuator are simulated. When the actuator is switched on, noticeable temperature drop is observed at all points in the substrate from those which existed when there has been a steady water flow in the channel. At the end of 20th cycle of actuation, the maximum temperature in the wafer has reduced by 5.4 K in comparison with the steady flow values. In comparison with the two-dimensional study which account for 17K reduction, it indicates that synthetic jet has only smaller beneficial cooling and has been over-estimated in the previous two-dimensional study.

Computational Study of the Synthetic Jet on Separated Flow Over a Backward-Facing Step

2010 ◽  
Author(s):  
Koichi Okada ◽  
Kozo Fujii ◽  
Koji Miyaji ◽  
Akira Oyama ◽  
Taku Nonomura ◽  
...  
Keyword(s):  
Shear Layer ◽  
Reynolds Stress ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Frequency Characteristics ◽  
Synthetic Jet ◽  
Recirculation Region ◽  
Backward Facing Step ◽  
Freestream Velocity ◽  
Jet Control

Frequency effects of the synthetic jet on the flow field over a backward facing step are investigated using numerical analysis. Three-dimensional Navier-Stokes equations are solved. Implicit large-eddy simulation using high-order compact difference scheme is conducted. The present analysis is addressed on the frequency characteristics of the synthetic jet for understanding frequency characteristics and flow filed. Three cases are analyzed; the case computing flow over backward facing step without control, the case computing flow with synthetic jet control at F+h = 0.2, and the case computing flow with synthetic jet control at F+h = 2.0, where non-dimensional frequency F+h is normalized with the height of backward-facing step and the freestream velocity. The present computation shows that separation length in the case of the flow controlled at F+h = 0.2 is 20 percent shorter than the case without control. Strong two-dimensional vortices generated from the synthetic jet interact with the shear layer, which results in the increase of the Reynolds stress in the shear layer region. These vortices are deformed into three-dimensional structures, which make Reynolds stress stronger in the recirculation region. Size of the separation length in the case of the flow controlled at F+h = 2.0 is almost the same as the case without control because the mixing between the synthetic jet and the shear layer is not enhanced. Weak and short periodic vortices induced from the synthetic jet do not interacts with the shear layer very much and diffuse in the recirculation region.

Numerical study of a transitional synthetic jet in quiescent external flow

2007 ◽  
Vol 581 ◽  
pp. 287-321 ◽  
Author(s):  
RUPESH B. KOTAPATI ◽  
RAJAT MITTAL ◽  
LOUIS N. CATTAFESTA III
Keyword(s):  
Numerical Study ◽  
Time Integration ◽  
Three Dimensional ◽  
Internal Flow ◽  
External Flow ◽  
Second Order ◽  
Synthetic Jet ◽  
Transition To Turbulence ◽  
Step Method ◽  
Fractional Step Method

The flow associated with a synthetic jet transitioning to turbulence in an otherwise quiescent external flow is examined using time-accurate three-dimensional numerical simulations. The incompressible Navier–Stokes solver uses a second-order accurate scheme for spatial discretization and a second-order semi-implicit fractional step method for time integration. The simulations are designed to model the experiments of C. S. Yao et al. (Proc. NASA LaRC Workshop, 2004) which have examined, in detail, the external evolution of a transitional synthetic jet in quiescent flow. Although the jet Reynolds and Stokes numbers in the simulations match with the experiment, a number of simplifications have been made in the synthetic jet actuator model adopted in the current simulations. These include a simpler representation of the cavity and slot geometry and diaphragm placement. Despite this, a reasonably good match with the experiments is obtained in the core of the jet and this indicates that for these jets, matching of these key non-dimensional parameters is sufficient to capture the critical features of the external jet flow. The computed results are analysed further to gain insight into the dynamics of the external as well as internal flow. The results indicate that near the jet exit plane, the flow field is dominated by the formation of counter-rotating spanwise vortex pairs that break down owing to the rapid growth of spanwise instabilities and transition to turbulence a short distance from the slot. Detailed analyses of the unsteady characteristics of the flow inside the jet cavity and slot provide insights that to date have not been available from experiments.

Water Synthetic Jet Driven by a Piezoelectric Actuator – LIF and PIV Experiments

2015 ◽  
Vol 1104 ◽  
pp. 45-50 ◽  
Author(s):  
Zuzana Broučková ◽  
Shu Shen Hsu ◽  
An Bang Wang ◽  
Zdeněk Trávníček
Keyword(s):  
Reynolds Number ◽  
Particle Image Velocimetry ◽  
Piezoelectric Actuator ◽  
Particle Image ◽  
Three Dimensional ◽  
Laser Induced Fluorescence ◽  
Synthetic Jet ◽  
Fluid Exchange ◽  
Image Velocimetry ◽  
Surrounding Fluid

A synthetic jet (SJ) is a fluid jet flow generated from fluid oscillations during a periodical fluid exchange between an actuator cavity and surrounding fluid. A water synthetic jet was generated from submerged piezoelectric-driven SJ actuator. The actuator slot width was 0.36 mm. The experiments were performed using laser induced fluorescence (LIF) flow visualization and particle image velocimetry (PIV) techniques, both in a phase locked setup. The LIF visualization was used to demonstrate three-dimensional nature of the SJ formation process and to estimate SJ velocity. The PIV experiment quantified SJ velocity cycles in chosen plans. The driven frequency was adjusted near the resonance at approximately 46 Hz. It was evaluated theoretically and confirmed experimentally by means of LIF visualization. The time-mean orifice velocity and the Reynolds number were estimated asU0= 0.07–0.10 m/s andRe= 100–150, respectively.

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