Mechanism of puff self-replication at lower Reynolds numbers

Determine the mechanism of puff self-replication (transition from one puff to two puffs) in constant–mass-flux pipe flow at Reynolds numbers around 2050–2100, where direct numerical simulations do not directly observe splitting events and the edge-tracking bisection algorithm yields a different edge state than the elongated-puff split edge identified at Re = 2200.

Background

The study identifies and validates a split edge state mediating puff replication at Re = 2200 and reveals a two-step slug-gap-split mechanism. At lower Reynolds numbers (e.g., Re = 2050 and Re = 2100), the bisection algorithm does not converge to the same split edge state; instead, it yields a distinct configuration and splitting events are too rare to be directly observed in DNS.

Because the decisive pathway for self-replication cannot be sampled at these lower Re, the authors explicitly state that the self-replication mechanism remains an open question in this regime.