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Research Papers: Techniques and Procedures

A Principle to Generate Flow for Thermal Convective Base Sensors

[+] Author and Article Information
Thien X. Dinh

Department of Mechanical Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japanthien@cfd.ritsumei.ac.jp

Yoshifumi Ogami

Department of Mechanical Engineering, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan

J. Fluids Eng 131(4), 041401 (Mar 11, 2009) (6 pages) doi:10.1115/1.3089538 History: Received June 25, 2008; Revised January 14, 2009; Published March 11, 2009

This paper presents a thin millimeter-scaled device that can generate a closed flow within itself with a velocity of the order of a few m/s. The device comprises a piezoelectric pump with a PZT membrane, housing chamber, and a closed network channel connected to the housing chamber through a specific throat. We investigate the device by computational fluid dynamics. This device is used to produce several free jet flows depending on the structure of the network channel. In this study, four jet flows comprising two perpendicular pairs of flows are demonstrated. If the PZT membrane vibrates within a suitable range, the self-similarity of the axial velocity (along the jet direction) to the cross distances scaled by the half-widths of the jet is observed for a certain range of axial distance. Each jet flow can bend almost freely in three dimensions. The two remaining flow components are small as compared to the axial component. The device potentially has wide applications in flow-based sensors.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Structure design of the device

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Figure 2

Working principle of the device

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Figure 3

Flow behavior at the throat in the discharge phase (a) and suction phase (b)

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Figure 4

Variation in the spatial-average axial velocity at the outlet of the nozzle against time. The maximum amplitude of the PZT membrane is 10 μm

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Figure 5

Profiles of u(x,0,z) and u(x,y,0) against z and y, respectively, for Θ0=15 μm

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Figure 6

Axial velocity of the jet against cross-distance for different amplitude vibrations of the membrane and different axial distance, x. The left-hand side of each figure shows a plot of u(x,0,z)/uc(x) against z/z1/2(x) and the right-hand side shows the variation in u(x,y,0)/uc(x) against y/y1/2(x).

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Figure 7

Axial velocity of the jet against cross-distance for different amplitude vibrations of the membrane at x=1.5 mm. The left-hand side of each figure shows a plot of u(x,0,z)/uc(x) against z/z1/2(x) and the right-hand side shows the variation in u(x,y,0)/uc(x) against y/y1/2(x). The approximate curve is plotted by Eq. 10.

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Figure 8

Variation in the center velocity against axial distance in the self-similar region

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Figure 9

Variation of half-widths against axial distance in the self-similar region. Black symbols z1/2(x), white symbols y1/2(x), circle Θ0=5 μm, upward-facing triangle Θ0=10 μm, and downward-facing triangle Θ0=15 μm.

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Figure 10

Variation of cross-stream velocity components with radial distance in the self-similar region. The left-hand side of each figure shows plots of v or w(x,0,z)/uc(x) against z/z1/2(x) and the right-hand side shows the variation of v or w(x,y,0)/uc(x) against y/y1/2(x).

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Figure 11

Time averaged velocity fields on two perpendicular planes containing the axis of the jet flow in the main chamber

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