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Flow Visualization of Ice-Water Morphodynamics in Turbulent Shear Flow

Diego Perissutti, Alfredo Soldati
(​Institute of Fluid Mechanics and Heat Transfer, TU-Wien, 1060 Vienna, Austria; Department of Engineering and Architecture, University of Udine)

Cristian Marchioli
(Department of Engineering and Architecture, University of Udine)

This animation shows the evolution of an ice–water interface obtained from a direct numerical simulation. An initially flat ice layer melts from below under a turbulent water flow, with warm water shown in dark blue and cold water in light blue. At early times, the ice surface develops turbulence-driven ice streaks aligned with the streamwise direction. As the simulation progresses, a morphological instability sets in, and spanwise wavy ice ripples spontaneously emerge. These ripples migrate slowly downstream while growing in amplitude over time.

Scientific Abstract:

The interaction between deep oceanic currents and the ice base of glaciers is a critical factor in accurately predicting global ice melting rates. However, current predictive models are frequently hindered by inaccuracies stemming from inadequate dynamical representations of the ice–water interface morphology. Large-scale turbulent shear-dominated flows induce complex interface evolutions that significantly alter local heat transfer and hydrodynamic drag. Because experimental data in these extreme oceanic conditions are difficult to obtain, high-fidelity numerical investigations are essential to uncover the scaling laws that govern ice roughness evolution and to bridge the gap between geophysical models and observations. The visualization presented here was obtained in 2025 through interface-resolved direct numerical simulations aimed at characterizing the dynamical evolution of the ice–water interface morphology. The data were generated using a pseudo-spectral, parallel, GPU-accelerated solver that couples the incompressible Navier–Stokes equations with a phase-field formulation and a volume-penalization immersed boundary method to resolve melting and freezing processes. The simulation captures the melting of a horizontal layer of ice subjected to a fully developed turbulent shear flow. To simulate a deep-water stream, a free-shear condition is imposed on the bottom boundary of the water layer, which is maintained at a bulk temperature above the melting point, while the top of the ice layer is kept below freezing. The animation illustrates the temporal evolution of the ice–water boundary at Reτ = 636 and a unifary Stefan number (ratio between the typical latent heat and sensible heat in the system). This visualization allowed us to recognize two distinct morphodynamical regimes: initially, the interface consists solely of streamwise streaky patterns. As the simulation progresses, a morphodynamical instability occurs, leading to the formation of a wavy pattern known as ice ripples. Previous work [1] has demonstrated that this instability emerges only at high shear Reynolds numbers, while subsequent studies [2] have shown that the morphodynamics and their characteristic scales are influenced by latent heat. Ongoing research is investigating these phenomena at even higher shear rates (Reτ up to 1600),

Selected Recent Publications

[1] Perissutti, D., Marchioli, C., & Soldati, A. (2024). Morphodynamics of melting ice over turbulent warm water streams. Int. J. Multiphase Flow, 181, 105007.

[2] Perissutti, D., Marchioli, C., & Soldati, A. (2025). Time and length scales of ice morphodynamics driven by subsurface shear turbulence. J. Fluid Mech., 1019, A34.