Capturing aerodynamic forces on wind turbine blades using a tip-corrected Actuator Line Method

The Actuator Line Method (ALM) is a technique used to simulate the aerodynamic performance of wind turbines in Large-Eddy Simulations (LES). It permits to capture the interaction and turbulence loading of wind turbine blades within turbulent atmospheric boundary layers. However, the approach has certain limitations, particularly when it comes to accurately capturing the radial loading distribution along the blades, especially towards the tip. This discrepancy arises because ALM represents the turbine blades as lines, and when coarse grid resolutions are used, the distance between the rotating line and the grid causes difficulties in realistically modelling the loads.

In large simulations of wind farms, this could constitute a serious limitation. To overcome this challenge, we have developed a simple tip-correction to the ALM approach that has a negligible computational cost and that consistently incorporates the Blade Element Momentum (BEM) tip-corrections within the ALM modelling framework. The validation of our tip-corrected ALM approach is made using BEM results for the NREL-5MW reference rotor under uniform inflow conditions. The comparison demonstrates that the results obtained from the tip-corrected ALM approach align with the BEM results that include tip corrections, as expected within the modelling framework. These findings indicate that our modified ALM approach effectively models tip-corrections even on coarser meshes, making it highly suitable for wind farm simulations.