Converging-diverging channel

Figure 2.18 Different channel shapes for which flow distributions have been computed, a zigzag (upper left), a sinusoidally curved (upper right) and a converging-diverging channel (bottom).

Figure 2.19 Streamline patterns in a converging-diverging channel for various Reynolds numbers, taken from [107. ...

Figure 2.28 Evolution of the temperature field in the recesses of a converging-diverging channel, as obtained by Wang and Vanka [122],...

The converging-diverging channel geometry for which Guzman and Amon [31] computed flow fields was also considered by Wang and Vanka [43]. They computed the flow and temperature field in an elementary cell of the channel based... 

Dynamical flow characterization of transitional and chaotic regimes in converging-diverging channels, J. Fluid. Mech. 321, (1996) 25-57. 

Stress field Shear in the overflight and in the channel High shear and elongation in the calendering gap, low in channels Uniftmn stress field, mainly shear convergent-divergent flow in mixing blocks... 

The area-velocity relation provides important insight regarding the behavior of a quasi-ID compressible flow in a channel of varying cross section. It states that for a subsonic flow (M < 1) to increase velocity, a decrease in cross-sectional area is required. This is an intuitive and familiar result similar to incompressible flow theory. In contrast, acceleration of a supersonic flow (M > 1), requires an increase in area a counter-intuitive result when viewed from an incompressible flow perspective. This relation also indicates that sonic velocity (M = 1) can only occur at a nozzle throat where the area is a minimum. It thus follows for a gas to expand from subsonic to supersonic velocities, it must flow through a convergent-divergent channel arrangement. 

Liquid flow patterns. Liquid entering a single-pass tray flows in a diverging channel until reaching the tray centerline, then in a converging channel as the outlet weir is approached. The liquid has little incentive to move sideways and follow the curved walls of the column. Instead, it seeks the shortest path from inlet to outlet, and channels through the tray center (Fig. 7.75). This leaves stagnant zones near the curved walls on the side. 

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