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مکانیک::
منطقه گردش
Laminar flow in backward-facing step possesses unique features including presence of circulation zones with strong gradients in the laminar regime that makes it suitable for our purpose without bringing other uncertainties such as turbulence modeling into the picture.
It is well known that there is a primary circulation zone behind the step in which its length (reattachment length) increases by increasing the Reynolds number.
As shown in Fig. 4.6, at higher Reynolds numbers (~300), a secondary circulation zone will form at the channel upper wall due to the adverse pressure gradient coming from sudden expansion at the edge of the step (Biswas et al. 2004).
Existence of circulation zones means longer residence time of the disperse phase in those regions; therefore, a higher degree of coalescence is expected in these zones.
Fig. 4.6 Circulation zones in a laminar backward-facing step flow at different Reynolds number (This figure was originally published in Chemical Engineering Science 102, 2013 and has been reused with permission)
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