Investigation of Rotor Models for Wind Turbine Simulations

Abstract

In this paper, air flow around a model wind turbine and the NREL offshore 5-MW baseline wind turbine is simulated using different rotor modeling techniques/methodologies. The actuator line (AL) method of modeling the rotor is compared with the fully resolved rotor simulation. The aerodynamic forces for the AL method are computed using an open source code, FAST, from NREL. An in-house code, Tenasi, is used to carry out the CFD simulations. Validation of the computational methodology is carried out by comparing the simulation results with the experimental data for the model wind turbine. Since the NREL offshore 5-MW baseline wind turbine is notional, experimental data is not available for validation. The simulation results are verified using the results from other studies. Nomenclature = projection width r = distance of the actuator (blade) point from the control volume F  = aerodynamic force computed using FAST f  = projected force on a control volume

An actuator‐line model with Lagrangian‐averaged velocity sampling and piecewise projection for wind turbine simulations

“…The simplest velocity sampling approach might be using the available wind velocity at the nearest fluid point. But as demonstrated in Mittal et al, 3 this approach would result in large oscillations due to the strong blade‐local effects. A more considered approach is to interpolate the velocity to the exact AL point location from nearby fluid points.…”

“…The proposed modifications are tested by simulating an NREL‐5MW concept wind turbine 35 . This wind turbine has been extensively studied in many previous works that provide a rich database for comparison 3,21,29 . It is a three‐blade turbine with a diameter of m. In this work, the rotational speed of 9.155 rpm is considered for a uniform freestream wind speed of 8 m/s, corresponding to a tip‐speed ratio (TSR) of 7.55.…”

“…Considering the intrinsic huge disparities in time and length scales in such simulations, 1 with the complex flow associated with the rotating blades, the traditional CFD approach which requires a fine resolution for the geometry is very challenging and expensive here. Nevertheless, some relevant works can be found in literature 2‐4 . Alternatively, parameterization or modeling of blade aerodynamic effects becomes more attractive and popular due to its much lower computational cost and reasonably high accuracy.…”

Wind Farm Power Prediction in Complex Terrain

“…The ALM can exhibit run times similar to a fully resolved rotor simulation due to time-step restrictions required to track the rotation of the actuator lines [40]. Additionally, it shows very similar wake velocity profiles [50] and power predictions [36] to the ADM-R. For these reason, we have chosen to focus on the application of the actuator disk models for this thesis.…”

“…Mittal et al investigated the effects of including the nacelle in wake model simulations and concluded that there are definite improvements in the wake velocity profiles [40].…”