The float-area-type flow meter, frequently known as a rotor meter, is an important fluid flow measuring device when the flow rate is small. The present work was undertaken in an effort to develop the fundamental investigation of performance of float-type flow meters and to get datas for designing them.
In the 1 st report, hydrodynamic analysis on laminar boundary layers around a float and an inner wall of tapered tube, is developed and relations about performance of various kinds of short or long floats are introduced. A drag coefficient of float is analytically expressed by a function of ιν/
C2Um where ι is the length of the part with maximum diameter,
C the minimum clearance, ν the kinematic viscosity of the fluid,
Um the mean fluid velocity at the minimum sectional area. The analytical formula of sensitivity of this flow meter is introduced and the effect of various factors (the taper of the tube, the drag coefficient and weight of the float, the clearance-diameter-ratio) is explained.
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