Ai Nakagawa and Takeo, R.M. Nakagawa

This paper is concerned with an exact solution of a circular cylinder in uniform viscous flow and its application to a flowmeter named Tension Thread Flow Meter. An analytical procedure to lead the exact solution for a drag of a circular cylinder suspended in a uniform viscous flow has been demonstrated, and it is found that the drag is proportional to the square of velocity weakly rather than the linear dependency on the velocity, as Stokes law for a sphere. When the Reynolds number Re < 0.4, the relation between the drag coefficient Cf and Re, as well as the drag of a circular cylinder in uniform flow and Re, have been derived and presented as simple analytical expressions. The theoretical results on the drag of a circular cylinder in a uniform flow have been applied directly to the prototype flowmeter, and to the velocity calibration for the selected scales of the thread, and their arrangements together with the velocity range, to be used. A prototype flowmeter has been manufactured and then deployed successfully to measure three velocity components in oscillatory waves. It is suggested that the potential of the flowmeter is almost limitless so that it is strongly recommended to develop the commercial version for general users, who are interested in measuring boundary layer flow, oscillatory wave, and turbulence.


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