Supercritical miniaturization of turbulence in microsystems

Abstract

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The onset of turbulence in microsystems remains a fundamental scientific and engineering challenge due to the dominance of viscous forces at small confined scales. This study, therefore, experimentally demonstrates the concept of Turbulence-On-a-Chip by generating and characterizing turbulent-like flow regimes in microconfined environments under high-pressure transcritical conditions, without the addition of any external force or passive strategy. A custom-built microfluidic test rig is developed to operate with CO2 at supercritical pressures and controlled temperature differences. Flow behavior is analyzed through external flow visualization and 2D time-resolved µPIV, revealing distinct laminar and turbulent-like regimes for the conditions evaluated. Laminar-like cases exhibit organized flow patterns and parabolic velocity profiles, while turbulent-like cases display irregular speckle patterns, particle migration, and optical distortions, indicative of flow destabilization through density-gradient effects. Complementary, direct numerical simulations provide deeper insight into the multiscale flow fluctuations, supporting the experimental results. These findings establish a new framework for microconfined turbulence generation, with ground-breaking implications for microfluidic mass transport and energy transfer.

This work is funded by the European Union (ERC, SCRAMBLE, 101040379). Views and opinions expressed are however those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. The authors gratefully acknowledge the Formació de Professorat Universitari scholarship (FPU-UPC 2023) of Universitat Politècnica de Catalunya · BarcelonaTech (UPC) (Catalonia), and the SGR program (2021-SGR-01045) of Generalitat de Catalunya (Catalonia).

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