In the numerical analysis of two-dimensional viscous flows, finite difference methods are usually used to solve the governing fluid flow equations which are taken to be the Navier-Stokes equation and the continuity equation in terms of stream function and vorticity.
In two-dimensional incompressible flow problems, the inflow and outflow passing through an arbitrary closed path in the flow region are equal in most cases.
There is a case, however, where the above-mentioned condition is not satisfied.
When equivalent sinks and/or sources exist in a multiply connected region, there is no flow balance and the well-known boundary condition, that stream function on a continuous solid wall is constant, cannot be satisfied. One example is the case where only one inlet or outlet port exists on the closed solid wall. The stream function on both side-walls of the port are equal, and the flow rate passing through this port is zero.
In this paper, the method of introducing two hypothetical discontinuous lines of the stream functions in the flow region is shown to analyze the flows having such a condition. Furthermore, a numerically analyzed example of the radial and circular two-dimensional steady flows around a hollow spool with ports, using this technique with the pressure condition is shown.

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As a part of a joint reaearch by the Research Committee on Lubrication of the Japan Hydraulics Pneumatics Society, an experimental study was made of the bearing/seal characteristics of the oil film between a valve plate and a cylinderblock of axial piston pump and motor, and the results obtained are reported.
With a test apparatus simulating the oil film of an actual pump and motor, oil film thickness, leakage flow rate, valve plate temperature and shaft torque were measured on the following test parameters, 4 types of valve plate with different sealing and/or pad area, shaft rotational speed 500-4000rpm, inlet pressure 20 MPa and below, petroleum base hydraulic fluid (inlet temperature 40°C (kinematic viscosity 30.0 mm²/s), 60°C (14.5 mm²/s)).
As a result, the effect of these parameters on the oil film thickness, and its fluctuation, the power loss and the degree of wear was made cleared.

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