the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 27 May 2024
Velocity correction for the Actuator Line Method
Abstract. We introduce a velocity correction designed to mitigate the overestimation of aerodynamic loads observed with the traditional Actuator Line Method (ALM) at the blades tip. The correction is based on Blade Element Momentum (BEM) theory to determine the ratio of tip-corrected to non-tip-corrected axial and tangential velocity components. These velocity ratios are used to correct the velocities at the blade locations, ensuring an accurate representation of aerodynamic effects near the blade tips. The correction only requires the Tip Speed Ratio (TSR), which can be estimated from local flow conditions and turbine specifications. This makes the method highly adaptable to various flow scenarios. The effectiveness of the proposed correction has been validated through Large Eddy Simulations (LES) at multiple inflow velocities through comparison against both BEM with tip correction and a vortex-based smearing correction for ALM.
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Status: open (until 29 Jun 2024)
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RC1: 'Comment on wes-2024-60', Anonymous Referee #1, 21 Jun 2024
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The authors are presenting a BEM-based velocity correction to the ALM. The AL velocities are scaled with the ratio of BEM induction with tip correction to BEM without tip correction. The paper defines the method with some minor shortcomings, however the method is in itself flawed. The authors seem to be unaware of nowadays well-established AL theory (multiple papers from different research groups), that the vortex-core smearing originating from the force distribution kernel, leads to missing some induction at the blade. The ALM thus needs a vortex-core or smearing correction that computes the missing induction, not a tip correction. The effect of the BEM tip correction on the blades' induction only behaves similarly to the one by the AL vortex-core smearing correction, as they both are related to the trailed vorticity. ALM simulations do not entirely lack the induction from the trailed vorticity, which BEM tip corrections correct for, but only a part of it in the core of the trailed vorticies due to force smearing. Medium-fidelity aeroelastic solvers actually use BEM together with vortex corrections instead of tip corrections. The authors also need to argue why it is beneficial to move to their proposed correction if other fast methods are already available. In terms of each flow solver iteration the cost of the AL correction is usually negligible.Â
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