Convective Heat Transfer Effects in Airfoil Icing

Various classic icing codes have been developed and used by the aircraft manufacturers to predict the ice shapes evolution. These codes apply boundary layer integral analysis, based on sand grain roughness, to estimate the convective heat transfer coefficient around the iced airfoil and adopt abrupt transition between laminar and turbulent flow. In the present work, the integral analysis is also used but a smooth laminar-turbulent transition model, based in the intermittency concept, is included. The transition onset position is estimated by classical empirical correlations or just imposed. The smooth transition model is included in the ONERA2D numerical code to predict ice shapes. The ice accretion on a NACA 0012 airfoil is simulated with the modified code and the results are compared with the ice shapes generated by ONERA2D original code and with experimental data. Additionally, it is presented the laminar-turbulent transition onset position and extension as well as sand grain roughness variation effects on the ice geometry.