# Hydrodynamic Study of Flow-Channel and Wall-Effect Characteristics in an Oscillating Hydrofoil Biomimetic Pumping Device

## TL;DR

This study explores how flow-channel design and wall spacing affect the performance of a biomimetic pumping device inspired by oscillating hydrofoils.

## Contribution

The study identifies key mechanisms of confinement-driven performance improvement in oscillating-hydrofoil pumps.

## Key findings

- Bidirectional-channel confinement improves pumping efficiency by 33.6% compared to single-channel and 62.7% compared to no-channel conditions.
- Wall spacing shows non-monotonic effects, with peak performance at extreme confinement (h/c=1.4) and moderate spacing (h/c=2.2–2.6).
- Two high-performance regimes are linked to jet-like transport and balanced momentum transport with reduced vortex losses.

## Abstract

To clarify how flow-channel configuration and wall spacing govern the hydrodynamic performance of an oscillating-hydrofoil biomimetic pumping device, this study conducted a systematic numerical investigation under confined-flow conditions. Using a finite-volume solver with an overset-grid technique, we compared pumping performance across three channel configurations and a range of channel–wall distances. The results showed that bidirectional-channel confinement suppresses wake deflection and irregular vorticity evolution, enabling symmetric and periodic vortex organization and thereby improving pumping efficiency by approximately 33.6% relative to the single-channel case and by 62.7% relative to the no-channel condition. Wall spacing exhibited a distinctly non-monotonic influence on performance, revealing two high-performance regimes: under extreme confinement (gap ratio h/c= 1.4), the device attains peak pumping and thrust efficiencies of 19.9% and 30.7%, respectively, associated with a strongly guided jet-like transport mode; and under moderate spacing (h/c= 2.2–2.6), both efficiencies remain high due to an improved balance between directional momentum transport and reduced vortex-evolution losses. These findings identify key confinement-driven mechanisms and provide practical guidance for optimizing flow-channel design in ultralow-head oscillating-hydrofoil pumping applications.