RUPTURE

All geophysical water flows are multi-phase flows, most of the time turbulent. This is the case for river and coastal flows, where sediments on an erodible bottom are transported in response to hydrodynamic forces with various small-scale processes. Understanding these sediment transport processes in turbulent flows is essential to predict sediment transport, and anticipate the long-term impacts of the multiplication of extreme events on rivers and coastal systems. Therefore, many attentions have been directed towards turbulence resolving two- phase flow simulations approaches, leading to significant advances in sediment transport modelling, in a will to tackle the challenge of understanding and accounting for the small- scale interactions between the flow turbulence and the dispersed particles. However, the validity of these models is constrained by our inability to provide high-resolution sediment flux (as a local product of the dispersed particles phase velocity and volume fraction) measurements in dilute and dense turbulent two-phase flows. Recently, only hydroacoustic techniques involving coherent Doppler sonars have offered means to resolve fluxes as well as second order turbulence statistics for the dispersed phase in dilute and dense flow conditions, and further suggest their potential to concurrently follow the fluid phase using the scattering properties of the turbulence itself, through the presence of turbulent microstructures formed by passive additive quantities.

RUPTURE will build on the most recent research in scattering theory, fluid mechanics and signal processing, implementing cutting-edge technology to produce comprehensive two-phase hydroacoustic flux measurements. RUPTURE will rely on a synergetic experimental and numerical approach to address its fundamental, analytical and methodological objectives. An experimental apparatus designed to reproduce isotropic turbulent single and two-phase flows using a calibrated micro bubble injection system, and its digital twin will assist RUPTURE in defining methodological scenarios for two-phase acoustic inversion, involving the contrasted scattering properties of turbulent microstructures and solid particles. This experimental/numerical synergy will provide an ideal environment to develop new generations of robust particle flux estimators in the frame of the statistical inverse theory, taking full advantage of the inherent stochastic nature of the echoes recorded by coherent Doppler sonars. The overall aim of these developments will be to investigate the dynamics of fine-scale sediment transport processes in dilute and dense geophysical aquatic flows, and their impacts on sediment fluxes. RUPTURE is the first attempt to develop a two-phase hydroacoustic inversion methodological frame using the flow turbulence properties recovered from passive additive quantities. This will enhance our understanding of hydroacoustic particle flux measurements, and therefore improve our ability to resolve and understand the fine-scale sediment transport processes that are yet to be fully accounted for in the recent turbulence resolved two-phase flow simulations, due to the lack of high-resolution experimental datasets.