Numerical Simulations of Flow Past a Truss Tower with an Evaluation of Tower Shadow Models for Wind Turbines
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- Institutt for fysikk 
The performance of steady-state tower shadow models for a wind turbine truss tower have been evaluated. The Reynolds-Averaged-Navier-Stokes (RANS) approach, in conjunction with the $k-omega$ Shear-Stress-Transport (SST) model, was used to simulate transient flows past cross sections of a truss tower. The objective was to compare numerical results with Powles', Blevins' and Schlichting's tower shadow models and evaluate their performance on a multimember structure. Parameters for each model have been estimated. It will be shown that the RANS model was able to reproduce realistic results when used in transient simulations on high Reynolds number flows (supercritical regime). The importance of considering unsteady motion when calculating the turbulence intensity, using RANS with transient simulations, will be explained. The multimember extension used for the tower shadow models reproduces the mean velocity profiles quite well, and by using a suitable estimation method, global parameters were found for all models. Additionally, turbulent inflow has been implemented with a user-defined function in Fluent. The results have been evaluated, and show that such such sophisticated inflow modeling is not necessary to predict realistic mean velocity profiles.