Design Optimization of Micro Synthetic Jet Actuator for Flow Separation Control

[+] Author and Article Information
Oktay Baysal

Frank Batten College of Engineering and Technology, Old Dominion University, Norfolk, VA 23529-0236obaysal@odu.edu

Mehti Köklü

Frank Batten College of Engineering and Technology, Old Dominion University, Norfolk, VA 23529-0236mkoklu@odu.edu

Nurhak Erbaş

Frank Batten College of Engineering and Technology, Old Dominion University, Norfolk, VA 23529-0236nerbas@odu.edu

J. Fluids Eng 128(5), 1053-1062 (Mar 08, 2006) (10 pages) doi:10.1115/1.2236134 History: Received August 10, 2005; Revised March 08, 2006

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.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 16

Obtained best case: Instantaneous stream traces of separation region, (a) no-control case (b) minimum volume stage, (c) maximum ingestion stage, (d) maximum volume stage, (e) maximum expulsion stage

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Figure 1

Schematic of the synthetic jet and its operation

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Figure 2

Separated flow (without control) in a channel with backward-facing step (Re=20). hc: Outlet channel height.

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Figure 3

Computational domain for straight channel: One of every third grid point is shown

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Figure 15

(a) Approximate surface enstrophy, J¯ens=function(A,f); do and W at their best values. (b) Approximate surface enstrophy, J¯ens=function(do,W); A and f at their best values.

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Figure 4

Deviation of centerline pressure (Eq. (8)) distribution through the micro duct for different computational models, Knin=0.088

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Figure 5

Variation of slip velocity along the microduct wall, Knin=0.088

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Figure 6

Cross-sectional view and the characteristics dimensions of the micro filter

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Figure 7

Micro filter and its computational domain

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Figure 8

(a) Normalized streamwise velocity variations along the centerline of micro filter. (b) Normalized streamwise temperature variations along the centerline of micro filter.

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Figure 9

Variation of shear stress along micro filter wall. Case I (top) and Case II (bottom).

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Figure 10

Micro backward facing step

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Figure 11

Streamwise variation of pressure

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Figure 12

Variation of normalized streamwise component of velocity

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Figure 13

Geometry of channel with backward facing step and synthetic jet actuator (oscillating membrane, triangular cavity, and orifice). For clarity, only every fourth grid line shown.

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Figure 14

(a) Plot of vorticity contours at maximum expulsion stage of the synthetic jet cycle. hc: Outlet channel height. (b) Velocity profile at the orifice exit for four different stages of the synthetic jet cycle.




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