Ice accretion studies on low Reynolds number UAV airfoil RG-15 – numerical validation

The accumulation of ice on airfoil surface can degrade its aerodynamic profile and affect the behavior of flow over the airfoil surface. Variation in surface characteristics can amend the aerodynamic behavior of an airfoil by triggering transition from laminar to turbulent flow. Ice accretion on manned aircraft flying at high values of Reynolds numbers were researched pervasively in the literature, but it is not simple to apply these findings to Unmanned Aerial Vehicle (UAV)s operating at low Reynolds numbers. Variation in Reynolds number of even one order of magnitude can have a substantial effect on the mechanics of ice accretion. Existing numerical ice accretion codes are validated for ice accretion at high Reynolds numbers but not at low Reynolds numbers. Consequently, an effort is made to perform ice accretion studies on UAV airfoil RG-15 at low Reynolds number on the order of 10 5 using ANSYS-FENSAP ICE. The numerical results are compared with icing tunnel experiments-based ice shapes available in the literature, and the associated aerodynamic penalties are studied numerically. Existing numerical algorithms can fairly predict the ice accumulation at low Reynolds number especially for rime ice cases. But the accuracy of prediction is compromised with increase in complexity of the problem associated with mixed and glaze ice, particularly in prediction the ice structure like roughness elements. For the cases considered in this study ice accretion has reduced the range and endurance of the UAV by 60%. The most significant numerical simulation issues associated with the use of Computational Fluid Dynamics (CFD) for ice accretion are also discussed.