Unforced flow regimes in planar baffled reactors with Smooth Periodic Constrictions

• Published in: Chemical engineering science Vol. 302; p. 120873
• Main Authors: Brandão, Sofia P., Brito, Margarida S.C.A., Ferreira, António A., Santos, Ricardo J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 05.02.2025
• Subjects: CFD; Flow regimes; Mixing; OFR; PLIF; Spectral analysis; CFD; Mixing; OFR; Flow regimes; PLIF; Spectral analysis
• ISSN: 0009-2509
• DOI: 10.1016/j.ces.2024.120873

•Three flow regimes were identified in baffled reactors without imposed oscillation.•Unforced flow frequencies were determined from spectral Fourier analysis.•Vortices’ formation in these reactors is described by the 2D turbulence theory.•Geometric parameters showed impact on dynamic flow onset in baffled reactors.•Basis for defining frequencies for implementation in oscillatory reactors. Flow regimes in two planar reactors with Smooth Periodic Constrictions, commonly used as Oscillatory Flow Reactors (OFRs), are characterized by Computational Fluid Dynamics (CFD) and Planar Laser Induced Fluorescence (PLIF) without applying the typical external oscillation to the flow. The unforced flow frequencies were identified by spectral Fourier analysis. Three different flow regimes were identified: steady/stratified laminar at low Reynolds numbers, unsteady laminar at intermediate Re, and turbulent flow at high Re. The CFD model was validated by comparison with the PLIF experimental results. A dual-double cascade, a 2D turbulence phenomenon, was detected, emphasizing the significant role of dynamic vortices’ formation in the reactors’ flow. Additionally, the geometric parameters, such as the reactor’s depth and constriction to the chamber’s width ratio, have shown a great impact on onsetting a dynamic flow. These results provide insights into the mixing mechanisms and dominant scales of the unforced flow, establishing the basis for future optimization of oscillatory parameters in OFRs.