Electrodes based on impinging jets

When a jet of fluid submerged in a medium of that fluid strikes a surface perpendicularly, it spreads out radially over that surface. Original interest in these systems was due to mass transfer investigations of downward directed jets of vertical-take-off aircraft [41], though other applications such as electrochemical machining are important. 

The laminar flow hydrodynamics for a radial wall-jet were first considered by Glauert [41] and subsequently by Scholtz and Trass [42]. A more complete evaluation for electrochemical purposes has recently appeared [43]. In Fig. 5 are shown the velocity profiles and schematic streamlines. Close to the wall we find 

a is the jet diameter and k is a constant approximately equal to unity. If we rewrite the velocity components as 

The ratio of limiting currents at ring and disc is once again 02/3. In order for eqn. (75) to be correct, and as can be seen from the streamlines in Fig. 5, a minimum nozzle exit/electrode separation is necessary [44, 45]. 

The wall-jet disc electrode is clearly not uniformly accessible (current density oc r s/4 ). Another important point is that iL depends on the three-quarter power of the flow rate it is more sensitive in this sense than rotating or tube/channel electrodes. 

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