Analysis of Roughness Correlations on Ice Geometries via Embedded Large-Eddy Simulation

This study uses embedded large-eddy simulations of a developing turbulent boundary layer over a heated flat plate with realistic ice roughness to assess local effects on velocity (Formula: see text) and thermal (Formula: see text) log-layer shifts. Validated against experimental data, the numerical setup is used to analyze the mean turbulent flow properties and ultimately assess a selection of equivalent sand-grain roughness Formula: see text correlations against computed roughness shifts. Several established models are taken into account that estimate equivalent sand-grain roughness distributions based on geometric properties of the nonuniform rough surfaces. The trend of Formula: see text and Formula: see text is observed by employing the different correlations. The analysis is complemented with a brief assessment of Stanton-number–friction factor analogies resulting from the simulation outputs. Finally, a multivariate approach is employed to investigate possible cross-dependencies between roughness geometrical properties and shifts. The results indicate that some existing models capture the trends of velocity shifts accurately only in the fully rough regime for Formula: see text, while for Formula: see text, they generally struggle to correctly capture the expected trends. Thermal shifts show inconsistent trends across the tested models. The same gap appears in Formula: see text estimates via friction analogies, showing no clear dependence on geometry features.