ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Alternating flattened tube microchannel design for effective non-Newtonian fluid mixing

Fatemeh Alipour, Morteza Bayareh, and Amir Torabi

Department of Mechanical Engineering, Shahrekord University, Shahrekord, Iran

E-mail: m.bayareh@sku.ac.ir

Received: 25 November 2025  Accepted: 4 January 2026

Abstract:

This study examines the micromixing performance of non-Newtonian fluids, characterized by shear-thinning and shear-thickening behaviors, in novel passive micromixer designs. Numerical simulations using the Carreau-Yasuda constitutive model are conducted to analyze fluid dynamics and species transport under varying flow conditions. The effects of key parameters such as Reynolds number (Re = 0.1 to 100), flow behavior index (n = 0.6 to 1.4), pitch angle (θ = 30° to 75°), and relaxation time (λ = 0.005 to 5 s) on the Degree of Mixing (DOM) and pressure drop (Δp) are systematically examined. Results demonstrate that the micromixer achieves a high DOM of up to 96.7% at low Re values through diffusion-dominated mixing and maintains efficient advection-driven mixing with a DOM of 86.7% at Re = 100. Increasing the pitch angle significantly enhances mixing, improving the DOM from 65% at 30° to over 95% at 75°, while Δp increases by 200%. Shear-thinning fluids exhibit superior mixing performance, with DOM decreasing from over 95% at n = 0.6 to below 70% at n = 1.4, accompanied by a 60% rise in Δp. Optimal mixing occurs at moderate relaxation times (around 0.05–0.1 s), where elastic effects maximize chaotic advection.

Keywords: Micromixers; Non-Newtonian fluids; Chaotic advection; Degree of mixing; Pressure drop

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04649-0

Chemical Papers 80 (4) 3787–3799 (2026)