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KURENAI : Kyoto University Research Information Repository

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= D<br />

V. 6 MAXIMUM HEIGHT OF RISING DROPLET<br />

' The maximum height which can be attained by a rising droplet in gas<br />

flowing vertically upward can be calculated by solving the equation of<br />

motion of the droplet by specifying the drag coefficient [68,69]. In this<br />

study, an analytical solution for a practical range of the droplet<br />

Reynolds number (Rep = 5 - 1000) has been obtained. From the maximum<br />

height of a rising droplet, the droplet velocity vh(D,jg,h) necessary to<br />

rise more than height h can be calculated as an inverse function.<br />

For the situation illustrated in Fig. 4, ,the equation of motion of a<br />

droplet in gas stream is formulated by<br />

and<br />

dv -ppg -4CDp<br />

pg (v-vg) Iv-vg1(67)<br />

ff<br />

dt=v(68)<br />

Here v, t, and y are the droplet velocity, time, and height from the pool<br />

surface_. In the above equations, it may be assumed that the droplet<br />

concentration is relatively small such that vg = jg. This implies that<br />

the relative velocity can be given by<br />

yr = v - v9 = v - jg(69)<br />

Initial conditions are given by<br />

v =<br />

Equations<br />

and drag<br />

dvr<br />

dt<br />

V.<br />

0<br />

att=0 .<br />

(67) and (68)<br />

coefficient for<br />

ep3<br />

f pg-4<br />

can be<br />

wake<br />

rewritten in terms of the relative<br />

regime given by Eq. (33) as<br />

10.67 (<br />

p 0.5 p v Iv 10.5<br />

pgD Pf r r•<br />

273<br />

velocity<br />

(70)<br />

(71)

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