Peristaltic pumping in thin non-axisymmetric annular tubes

Area of Science:

• Fluid Dynamics
• Biomedical Engineering
• Computational Science

Background:

• Peristaltic flow is crucial in biological systems and industrial applications.
• Previous studies focused on 2D models in simple geometries like tubes and concentric annuli.
• Non-axisymmetric geometries, like those found in perivascular spaces, present unique flow dynamics.

Purpose of the Study:

• To investigate the three-dimensional nature of peristaltic flow in a non-axisymmetric annular tube.
• To model the flow dynamics in an eccentric annular space with an elliptical outer boundary.
• To analyze the impact of geometric parameters like ellipticity and eccentricity on flow characteristics.

Main Methods:

• Numerical simulations using a finite-element scheme.
• Modeling the annulus with an inner circular wall and an outer elliptical wall, allowing for eccentricity.
• Simulating flow driven by a propagating sinusoidal radial displacement of the inner wall.

Main Results:

• The flow in a non-axisymmetric annulus is fully three-dimensional, featuring azimuthal pressure variations.
• Azimuthal flow is induced, causing streamlines to wiggle, especially in narrower gaps.
• Time-averaged volumetric flow is consistent with the peristaltic wave direction.
• Flow rate decreases with increasing ellipticity of the outer wall or eccentricity of the annulus.

Conclusions:

• Non-axisymmetric geometry fundamentally alters peristaltic flow, introducing 3D effects.
• Geometric parameters significantly influence the flow rate and patterns.
• Azimuthal shearing enhances mixing and Taylor dispersion, suggesting potential applications in transport and mixing processes.