Experimental exploration of free surface turbulence: towards strong regimes
Open Access DepositedFree surface (FS) flows are of central importance in many engineering applications including ocean and environmental engineering, and naval hydrodynamics. Despite significant advancements in experimental and computational fluid dynamics, complex physical phenomena that arise at the air-water interface (e.g., turbulent transport, mixing, and bubble entrainment) are still not fully understood. This is mainly due to the multiscale and multiphase nature of these flows and an intricate interaction between the FS boundary and the turbulent field underneath. Validation and further advancement of the numerical models require challenging experimental measurements of the interfacial topography and the turbulent field.This study presents a new, non-intrusive experimental diagnostic for reconstruction of liquid-gas interfaces in the three-dimensional (3D) space, and introduces a new experimental facility to characterize free surface turbulence in stronger turbulence regimes than previously achieved. The surface reconstruction algorithm relates the optical deformations of a submerged, laser-induced fluorescent grid to the instantaneous profile of the surface through which the grid is captured, based on a ray tracing approach. The grid is written on a vertical plane, directly in the liquid phase. The adoption of the Talbot-effect structured illumination scheme for the tagging of the grid in the liquid phase enables spatio-temporal flexibility, while the vertical orientation of the laser plane provides boundary conditions for the surface reconstruction and minimizes restrictions of existing profilometry schemes. The proposed design for the free surface turbulence facility provides stronger turbulent condition than previously achieved without sacrificing flow quality; flow quality metrics (e.g., homogeneity coefficient) are on par with previous facilities. This allows us to experimentally explore the turbulence structure for the first time in this flow regime. Alternative flow tracers are proposed to tackle challenges encountered experimentally in strong turbulent conditions. Turbulent statistics are investigated for mainly two turbulent conditions -at and post- the onset of the turbulent air entraining regime, revealing an intriguing interaction between the turbulent field and the FS.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.