Analysis of Low Reynolds Number Flow in Nozzle and Diffuser

(1)

ǵܟ-ʶझۊ ǅؓԅڗ ۊ Reynolds Վ ٿʅࢳԒ ऺԆ

暧勆汆

·

^決渆柣

^*

Analysis of Low Reynolds Number Flow in Nozzle and Diffuser

Gwi-Eun Song and Joon-Sik Lee

Key Words : Nozzle(

), Diffuser(

), Separation(

), Micropump(

) Abstract

An investigation of low Reynolds number flow in nozzles and diffusers which are widely used in the valveless micropump is presented. Flow characteristics in the nozzle and diffuser are explained in view of viscous effect and flow oscillation induced by pumping membrane. These calculation results show that the rectification property of valveless micropump is due to a flow separation in the diffuser and the separation is largely originated from the flow oscillation. Under the assumptions of steady flow velocity profile and flow separation in the diffuser, simplified analytical models are provided to see the dependency of rectification on the micropump geometry. Geometric parameters of channel length, nozzle throat, chamber size, and converging/diverging angle are depicted through the analytical models in low Reynolds number flow, and the prediction and experimental results are compared. This theoretical study can be used to determine the optimum geometry of valveless micropump.

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diverging channel

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rectification ratio

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Fig. 8

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S Y

Z

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RS TU

V

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KLM

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η η η η

0 10 20 30 40 50

K

0.65 0.70 0.75 0.80 0.85 0.90 0.95

α^{= 1}ô α^{= 2}ô α^{= 3}ô α^{= 4}ô

η η η η

0 10 20 30 40 50

εεεε

0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20

α^{= 1}ô α^{= 2}ô α^{= 3}ô α^{= 4}ô

Fig. 7 Rectification efficiency with different nozzle/diffuser channel length

α α α α

0 2 4 6 8 10

K

0.60 0.65 0.70 0.75 0.80 0.85 0.90

η^{= 40} η^{= 60} η^{= 80} η^{= 100}

α α α α

0 2 4 6 8 10

εεεε

0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22

η = 40 η = 60 η = 80 η = 100