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The problem of obtaining a numerical solution for the steady flow between two coaxial infinite disks, one fixed and porous, the other rotating, is reduced by von Kámán's hypothesis to solution of a system of nonlinear equations. A Newton-type iteration results in several solutions to these equations, as a number of authors have already indicated. Nevertheless, an interval in which only one solution is found exists for small values of the Reynolds number based on the angular velocity of the rotating disk, the distance between the disks and the kinematic viscosity of the fluid. At large values of this Reynolds number, two solutions appear and have been the subject of intense controversy.In this paper, both physical and numerical arguments are presented which support a Batchelor-type solution for the flow between infinite disks, in which part of the fluid rotates as a solid body. The other solution, following Stewartson, assumes that the velocity of the fluid outside the boundary layers is entirely axial. This only seems to be verified experimentally when the distance between the disks is large compared with the (finite) radius of the disks.

The present paper describes an experimental investigation of the various parameters affecting the operation of industrial pneumatic controllers based on the jet nozzle principle. A test rig was built to monitor supply pressure, air temperature, airflow characteristics, and the static pressure distribution over the flat plate on which the jet impinges. The results demonstrate the existence of a low pressure, separated flow zone, subject to fouling, which subsequently was eliminated by appropriate changes of the injection nozzle geometry. The previous experimental findings were also confirmed by numerical simulation of the flow. Experimental results also show that the internal diameter of the regulator, situated inside the measuring branch, has an important influence on the sensitivity of the apparatus, as well as influencing its range.

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An experimental investigation of the frequency response of electrochemical probes to transversal velocity fluctuation is reported. The study has been focused on wall shear stress for a modulated flow due to an oscillating cylinder along its own axes since the wall shear stress has been first numerically determined for this flow. Results indicate that a frequency response correction to probe outputs is required and that this correction depends on the amplitude of fluctuations.