Regularized thin-fiber model for nanofiber formation by centrifugal spinning

Area of Science:

• Fluid dynamics
• Materials science
• Rheology

Background:

• Modeling fiber formation from rotating nozzles is complex due to coupled forces.
• Previous models faced numerical limitations in capturing steady-state behavior.
• Understanding the influence of viscosity on fiber dynamics is crucial.

Purpose of the Study:

• To develop a regularized thin-fiber (string) model for analyzing viscous fiber emergence from a rotating nozzle.
• To determine steady fiber velocity and diameter under centrifugal, inertial, and viscous forces.
• To investigate the role of dimensionless parameters (Rossby and Reynolds numbers) in fiber behavior.

Main Methods:

• Proposed a regularized thin-fiber (string) model to overcome numerical limitations.
• Analyzed fiber dynamics considering centrifugal, inertial, and viscous forces.
• Investigated the influence of the Rossby number (Rb) and Reynolds number (Re) on fiber trajectory and diameter.

Main Results:

• Regularization is necessary for numerical stability when Rb < 0.5 and Re < 1.
• Viscosity reduces fiber trajectory curvature in the stable regime, leading to a viscosity-independent diameter for sufficiently long fibers.
• At Rb > 0.5, viscosity increases curvature, and solutions do not converge to the inviscid result.

Conclusions:

• The regularized string model provides stable solutions for viscous fiber formation.
• Fiber behavior is distinctly categorized by regimes in the Re-Rb plane.
• Viscosity's impact on fiber trajectory and final diameter depends critically on the interplay between inertial, centrifugal, and viscous forces.