An axisymmetric unsteady flow of incompressible viscous liquid in a circular rigid tube was studied for some aspects. Change of the axial velocity profile at a cross section, due to a step change of the flow rate, was obtained analytically except the inletlength region. In the experiment a laser Doppler velocimeter was used to measure the velocity profile without disturbing the flow. The experimental results are found to be in good agreement with the predictions of the analysis and the base of the so-called frequency dependent viscous friction for the unsteady flow in the tube was supported by this research from the viewpoint of the local dynamic behavior of the flow.

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The development of a fluithc sensor foe a manerically controlled positioning syssem is treated in this paper. The laminar jet sensor is known as such a sensor, but this sensor is highly sensitise to acoastic noise and moreover the owtput resistance is so high that it is not connectable to wall attachment fluidic logic. As an objective sensor, a ring jet sensor shows digital characteristics, but the response to the approach from the transversal direction is not known.
Therefore this research was stated by observing the transversal characteristics and through the design of the ring nozzle and control plate (object), developed a positioning sensor system with on-off cratput signsk.
One of the main feataxes of this sensor system is to utilise a control plate with the width narrower than the character of the ring jet and with the carved leading surface whose curvature is same to that of the ring jet. This system results in part of the ring jet attaching to and separating from the leading surface of the control plate.
The hysteresis of the sensor to the movement of the control plate varies from about Ism to 15μm. and is adequate for this application. The ring jet sensor is comparatively stable against some cirounferential emditionss and its output resistance is reasonably low to be suitable for comnection with fluidic elements.

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