Scaling Laws for the Propulsive Performance of Three-Dimensional Pitching Propulsors

TL;DR

This paper develops and validates new three-dimensional scaling laws for the thrust and energetics of pitching propulsors, incorporating complex flow effects and providing insights for bio-inspired propulsion system design.

Contribution

It extends existing two-dimensional scaling laws to three dimensions by including added mass, vortex effects, and vortex topology, validated through simulations and experiments.

Findings

Scaling laws accurately predict thrust and power across various parameters.

Three-dimensional effects significantly influence propulsor performance.

Guidelines for designing efficient bio-inspired propulsion systems are provided.

Abstract

Scaling laws for the thrust production and energetics of self-propelled or fixed-velocity three-dimensional rigid propulsors undergoing pitching motions are presented. The scaling relations extend the two-dimensional scaling laws presented in Moored & Quinn (2018) by accounting for the added mass of a finite-span propulsor, the downwash/upwash effects from the trailing vortex system of a propulsor, and the elliptical topology of shedding trailing-edge vortices. The novel three-dimensional scaling laws are validated with self-propelled inviscid simulations and fixed-velocity experiments over a range of reduced frequencies, Strouhal numbers and aspect ratios relevant to bio-inspired propulsion. The scaling laws elucidate the dominant flow physics behind the thrust production and energetics of pitching bio-propulsors, and they provide guidance for the design of bio-inspired propulsive systems.