Study of implicit CFD modeling of riblets on wind turbine airfoil in transitional flow

Abstract

The study introduces a novel hybrid boundary condition, derived from existing literature, crafted for predicting the impact of riblets on airfoils in transitional flow. In contrast to models tailored for fully turbulent flow, the hybrid approach successfully captures the operational dynamics of riblets, as demonstrated through meticulous testing. The boundary condition integrates slip length and a modified specific dissipation rate (ω) boundary to encompass the entire riblet regime. Adjusting the model to match measured drag behavior enables predictions of riblet effects at higher Reynolds numbers pertinent to wind turbine blades. Validation reveals the model’s proficiency in capturing the order of magnitude in drag reduction and aligns the change in drag in the correct direction for diverse riblet heights, yet highlights discrepancies in replicating absolute drag reduction values, particularly at smaller angles of attack. This underscores the imperative for further refinement and tuning, necessitating additional experimental data at higher Reynolds numbers and across various angles of attack to ensure the model’s robust applicability across a broader spectrum of conditions.