Square constrictions geometry

The flow coefficient of the square constriction cannot be solved analytically. It was determined numerically by the solution of equation 3 for the geometry shown in Figure 4. The geometry in figure 4 is mapped into a rectangle and the problem is solved with a Galerkin spectral technique. The relation between the flow coefficient and interface position is shown in Figure 5 for the surfactant free system. 

A simple three-dimensional FF geometry can be obtained by fitting a cylindrical capillary tube, with a constriction of 50-350 tm at its entrance, very closely into a square capillary tube [74]. This device resulted in suspensions of nitrogen bubbles of 50-900 tm in water solutions with a gas fraction as large as 90%. The following... 

Whereof and Reef are constriction based friction factor and Reynolds number respectively, and Po is the Poiseuille number specific to the cross-sectional geometry of the channel, 16 for circular pipes, 14.23 for a square channel and 24 for flow between two parallel plates. 

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