Large-Eddy Simulation of Accelerating Thermal Boundary Layers over Ice Roughness

This study employs embedded large-eddy simulation (ELES) to analyze favorable-pressure-gradient effects on convective heat transfer from realistic roughness based on laser-scanned, unwrapped airfoil ice shapes. Flow acceleration is introduced by a systematic variation of the domain upper shape to mimic the effect of a wind-tunnel ceiling insert. Skin friction ([Formula: see text]) and Stanton number ([Formula: see text]) trends are analyzed, as well as turbulent flow properties, to assess the effect of various FPG configurations on convection with reference to the zero-pressure-gradient (ZPG) configuration. Validation against experimental data confirms that ELES captures the coupled effects of ice roughness and pressure gradients on aerodynamic and thermal behavior while supporting the use of a simplified flat-plate configuration as a reliable surrogate for more complex airfoil geometries. Flow acceleration primarily modifies the pressure-induced contribution to skin friction, while the scaled Stanton number distribution remains essentially unchanged. For the present cases, this indicates that flow acceleration reinforces the local pressure-gradient effects induced by the roughness, thereby promoting a further breakdown of the Reynolds analogy. These observations are supported by local flow behavior close to the roughness, visualized through instantaneous and averaged turbulent fields.