DETACHED-EDDY SIMULATION FOR SYNTHETIC JETS WITH MOVING BOUNDARIES

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1429-1434 ◽  
Author(s):  
HAO XIA ◽  
NING QIN
Keyword(s):  
Boundary Layers ◽  
Moving Boundary ◽  
Turbulent Boundary Layers ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Moving Boundaries ◽  
Time Dependent ◽  
Jet Flows ◽  
Detached Eddy Simulation ◽  
Eddy Simulation

A Detached-Eddy Simulation (DES) with moving boundaries has been developed and applied to synthetic jet flows. Complex unsteady flow patterns of the flows were revealed from the simulation. Comparisons between the simulation and experiments showed reasonably good agreements, which indicates that, as a hybrid RANS/LES method, DES is capable of handling unsteady separations with turbulent boundary layers and time-dependent moving boundary conditions.

Design Optimization of Micro Synthetic Jet Actuator for Flow Separation Control

2006 ◽  
Vol 128 (5) ◽  
pp. 1053-1062 ◽  
Author(s):  
Oktay Baysal ◽  
Mehti Köklü ◽  
Nurhak Erbaş
Keyword(s):  
Design Methodology ◽  
Moving Boundary ◽  
Stokes Equations ◽  
Wall Slip ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Recirculation Region ◽  
Flow Separation Control ◽  
Analysis And Design ◽  
Design Variables

A computational analysis and design methodology is presented for effective microflow control using synthetic jets. The membrane is modeled as a moving boundary to accurately compute the flow inside the jet cavity. Compressible Navier-Stokes equations are solved with boundary conditions for the wall slip and the temperature jump conditions encountered for a specific range of Knudsen numbers. For validation, microchannel flow and microfilter flow are successfully computed. Then, flow past a backward-facing step in a microchannel is considered. Analysis is coupled with a design methodology to improve the actuator effectiveness. The objective function is selected to be the square of the vorticity (enstrophy) integrated over a separated region. First, from a design of experiments study, orifice and actuator cavity widths are identified as the most effective design variables. Then, a response surface method is constructed to find the improved control of the flow. This optimization results in more than 83% reduction of the enstrophy of the recirculation region.

Study on the Flow Characteristics of Synthetic Jets Near a Rigid Plane Boundary

2011 ◽  
Author(s):  
Ryota Tsunoda ◽  
Koichi Nishibe ◽  
Yuki Fujita ◽  
Kotaro Sato ◽  
Kazuhiko Yokota ◽  
...  
Keyword(s):  
Flow Characteristics ◽  
Maximum Velocity ◽  
Stokes Number ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Plane Boundary ◽  
Jet Flows ◽  
Rigid Boundary ◽  
Wire Method ◽  
Rigid Plane

The jet flows have been applied to various fields to control the flow separation. Over the last decade, several studies have investigated synthetic jets. However, there are still many clarifications needed, including details of the structure and Coanda effect of synthetic jets. The present study clarifies some fundamental flow characteristics of free synthetic jets and synthetic jets near a rigid boundary by conducting an experiment and numerical simulations. As the main results, it is found that the velocity distribution of free synthetic jets depends on K = Re/S2 (the ratio of the Reynolds number to the square of the Stokes number) and can be identified by the maximum velocity at the centerline and the jet half-width. Flow visualization is carried out applying the smoke wire method. In addition, it is confirmed that the flow characteristics of the synthetic jet near a rigid boundary and re-attachment length of the synthetic jet are determined not only by H1/b0 (normalized step heights) but also K.

Effective Range of Micro and Synthetic Jets for Flow Control

2005 ◽  
Author(s):  
Mehti Koklu ◽  
Nurhak Erbas ◽  
Oktay Baysal
Keyword(s):  
Flow Control ◽  
Moving Boundary ◽  
Rarefied Gas ◽  
Oscillation Amplitude ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Navier Stokes ◽  
Rarefied Gas Flows ◽  
Design Variables ◽  
Primary Focus

Effectiveness of two-dimensional synthetic jet is studied using numerical simulations. A Navier-Stokes (NS) solver for moving and deforming meshes has been modified to investigate numerically the diaphragm-driven flow in and out of two synthetic jet cavity geometries. Compressible flow simulations are required for rarefied gas flows to accurately predict the micro flow field. The solver is modified to accommodate slip wall boundary condition proposed in literature for micro scale flow problems. The piezoelectric-driven diaphragm of the cavity is modeled in a realistic manner as a moving boundary to accurately compute the flow inside the jet cavity. The primary focus of the proposed paper will be on the analysis of the design space determined by the geometric and flow-type design variables that identify the effectiveness of the synthetic jet by means of the orifice jet velocity and local jet momentum rate. The design variables are the membrane oscillation frequency (f), membrane oscillation amplitude (A), orifice width (d), and membrane width (W). The present computations for jet discharging into quiescent medium reveal that these variables have determining effects on the flow control parameters, which are the jet exit velocity, local momentum rate, as well as vortex shedding from the orifice.

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