Secondary motion in three-dimensional branching networks.

Area of Science:

• Fluid Dynamics
• Computational Fluid Mechanics
• Biofluidics

Background:

• Secondary motion in fluid flow is crucial in branched networks, yet its generation, distribution, and evolution are complex.
• Previous studies often simplify network geometry, limiting understanding of intricate flow dynamics in multi-generational systems.

Purpose of the Study:

• To comprehensively document the generation, 3D distribution, and evolution of secondary motion in a six-generation branched network.
• To quantitatively evaluate the impact of planar versus non-planar configurations on fluid dynamics within the network.

Main Methods:

• Numerical computation of six generations (G0-G5) of a branched network, involving 63 straight portions and 31 bifurcation modules.
• Utilized over 30 million computational elements for high precision and detailed flow visualization.
• Formulated three new quantitative parameters: secondary flow non-uniformity index ([Formula: see text]), mass-flow-averaged relative kinetic energy of secondary motion (E), and inter-branch secondary flow non-uniformity ([Formula: see text]).

Main Results:

• Straight portions generally attenuate secondary motion, while complex bifurcation modules generate and modify vortices.
• Out-of-plane configurations create more secondary kinetic energy and less inter-branch non-uniformity compared to in-plane arrangements.
• New parameters quantify secondary flow features, showing E increases with generation and is higher in daughter branches with greater mass flow.

Conclusions:

• The 3D arrangement of branches significantly influences secondary flow characteristics.
• Bifurcation modules are key generators of secondary motion, impacting vortex structure and energy.
• The study provides a robust framework for analyzing complex secondary flows in branched systems.