A rectangula r j et from a long channel with a rectangular exit of an aspect ratio of five was vertically impinged on a flat plate. Taking the impingment distance as the parameter, the pattern of impingementf l ow, the velocity on the jet centerline and the pressure distribution on the flat plate were examined. Smoke of joss-sticks was used to observe the flow patterns. The pressure on the flat was measuredt horough0.5. mmd iameter holes on the plate. Impingemendt istances were within 30 times the length of the short side of the rectangular exit. The flow patterns on the impingementp late are found t o change twice with increasing impingement distance. Some streamlines, not only on the large end plate but also on the impingementp late, form toward the jet exit at distant regions from both axes of the two plates in the case of small impingementd istances. In addition, the spread of pressure distributionso n the impingementp late is presentedf or different impingementd istances.

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Instantaneous flowrate measurement is required to elucidate the high frequency characteristics of oil hydraulic control components and systems. However, the method of unsteady flowrate measurement with high frequency response and high accuracy has not been established.
In this research, a new instantaneousf lowmeterf or oil hydraulics using cylindrical chokes is proposed and developed. In this method the instantaneous flowrate through chokes is predicted in real time from measurement of pressure difference on both sides of cylindrical choke through the numerical operation of the transfer function with nonlinear relation between flowrate and pressure drop, which has been established for cylindrical chokes.
The samplingf requencyc an be set at 12.8Hk z to maintain high response, e mployinge xclusive parallel operating circuits for multiplicationsa nd sums.
The results of frequency response between flowrate and pressure for hydraulic pipelines measured by the newly developed instantaneous flowmeter are in good agreement with those measured by LDV instantaneous flowmeter which has been established by authors and used for calibration. Moreover, recorded figures of unsteady flowrate obtained by the developed flowmeter in real time coincide well to a great extent with those obtained simultaneously by LDV instantaneousf lowmeter.

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