Wake Modelling using an actuator disk model in openFOAM

Abstract

Two "Blind tests" have been performed at NTNU. Researchers were asked to send in results from a simulation of a model turbine in a wind tunnel to compare the different results with the measured values. There was a large spread in the simulation results, showing that additional testing and development needs to be made in order to increase the accuracy of the modelling methods.This thesis uses the "Blind test 1" as the set-up for the numerical simulations, and the actuator line code created by NREL to model the wind turbine. The actuator line method divides each blade into actuator line elements and distributes the forces from the line elements onto the grid.A parameter study has been performed using the actuator line code, and guidelines have been created describing how to use the code to achieve the best possible results. This thesis has pointed out a few current problems with the actuator line implementation, including a difficulty with achieving a grid independent solution. The actuator line code mostly overestimated both thrust and power compared to the experimental values, and the best results where found from the grid producing the minimum thrust and power values.The numerical results have been compared to the "Blind test 1" and "Blind test 2" experimental values, including thrust, power and velocity deficit and turbulent kinetic energy in the wake behind the turbines. The hub and tower has been included in the numerical simulation, proving to have a large effect on the turbulent kinetic energy.The conclusion is that by following the introduced guidelines, the method is able to predict the experimental results from both of the "Blind tests" in a good manner.