Early turbulence and pulsatile flows enhance diodicity of Tesla's macrofluidic valve

TL;DR

This study investigates Tesla's macrofluidic valve, revealing that early turbulence and pulsatile flows significantly enhance its diodic performance, with potential applications in fluidic mixing and pumping.

Contribution

The paper demonstrates how early turbulence and pulsatile flows improve the diodicity of Tesla's macrofluidic valve, providing insights into inertial flow physics at low Reynolds numbers.

Findings

Diodicity sharply increases at Re ≈ 200.

Flow instabilities suggest a laminar-to-turbulent transition.

Pulsatile flows boost diode performance.

Abstract

Microfluidics has enabled a revolution in the manipulation of small volumes of fluids. Controlling flows at larger scales and faster rates, or $\textit{macrofluidics}$, has broad applications but involves the unique complexities of inertial flow physics. We show how such effects are exploited in a device proposed by Nikola Tesla that acts as a diode or valve whose asymmetric internal geometry leads to direction-dependent fluidic resistance. Systematic tests for steady forcing conditions reveal that diodicity turns on abruptly at Reynolds number $\textrm{Re} \approx 200$ and is accompanied by nonlinear pressure-flux scaling and flow instabilities, suggesting a laminar-to-turbulent transition that is triggered at unusually low $\textrm{Re}$. To assess performance for unsteady forcing, we devise a circuit that functions as an AC-to-DC converter, rectifier or pump in which diodes transform imposed oscillations into directed flow. Our results confirm Tesla's conjecture that diodic performance is boosted for pulsatile flows. The connections between diodicity, early turbulence and pulsatility uncovered here can inform applications in fluidic mixing and pumping.