Experimental investigation of turbulence in non-Newtonian fluids using ultrasound velocity profiling
Year: 2025
Type: article
Abstract: Pipeline transportation of non-Newtonian fluids (NNFs) is a cornerstone of modern infrastructure. While the laminar and transitional regimes have been widely explored, the turbulent flows of NNFs remain poorly understood. This study experimentally investigates fully developed, high turbulent pipe flow of NNFs (Reynolds No. ≈ 100,000–660,000) by analyzing wall shear stress and velocity profiles obtained via Ultrasound Velocity Profiling. We observe that the transition to the logarithmic law region is delayed due to an increase in the size of micro-eddies, leading to a thicker laminar sublayer. At lower concentrations (mildly non-Newtonian conditions), the log-law intercept shifts upward. However, with increasing concentration, viscoplastic effects stabilize the effective viscosity, causing the log-law intercept to approach Newtonian scaling. This trend appears to result from the competing influences of shear-thinning—initially promoting turbulence and momentum transfer—and viscoplastic damping at higher concentrations, which suppress turbulence and reduce drag. In the second part of the study, a comparative analysis of numerical models shows that semi-empirical approaches fail to accurately capture near-wall velocity gradients, resulting in significant wall shear stress errors. These discrepancies stem from the models’ inability to account for turbulence suppression and redistributed shear stress under shear-thinning conditions. Incorporating rheology-based wall functions into standard Newtonian models significantly improves wall shear stress predictions but still underperforms near the wall. Refining model constants through a data-driven approach may improve accuracy, but this requires advanced experimental and numerical studies of near-wall turbulence to develop reliable models for industrial applications.
Authors: B.K. Yusufi, Z. Kapelan, D. Mehta
Institution: Delft University of Technology
Language: English
Subfield: Fluid Flow and Transfer Processes
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,720
Funder: Technische Universiteit Delft
OpenAlex ID: W4416667202