Large eddy simulation of dynamically controlled wind turbines in an offshore environment

Abstract

Accurate modelling of transient wind turbine wakes is an important component in the siting of turbines within wind farms because of wake structures that affect downwind turbine performance and loading. Many current industry tools for modelling these effects are limited to empirically derived predictions. A technique is described for coupling transient wind modelling with an aero-elastic simulation to dynamically model both turbine operation and wake structures. The important feature of this approach is a turbine model in a flow simulation, which actively responds to transient wind events through the inclusion of controller actions such as blade pitching and regulation of generator torque. The coupled nature of the aero-elastic/flow simulation also allows recording of load and control data, which permits the analysis of turbine interaction in multiple turbine systems. An aero-elastic turbine simulation code and a large eddy simulation (LES) solver using an actuator disc model were adapted for this work. Coupling of the codes was implemented with the use of a software framework to transfer data between simulations in a synchronous manner. A computationally efficient simulation was developed with the ability to model turbines exhibiting standard baseline control operating in an offshore environment. Single and multiple wind turbine instances were modelled in a transient flow domain to investigate wake structures and wake interaction effects. Blade loading data were analysed to quantify the increased fluctuating loads on downwind turbines. The results demonstrate the successful implementation of the coupled simulation and quantify the effect of the dynamic-turbine model.

From meso-scale to micro scale LES modelling: Application by a wake effect study for an offshore wind farm

“…These observations are in agreement with previous LES [5,7]. We will now investigate for this reason by means of higher momentum analyses.…”

“…The "tunnel's walls" are much thicker and its radius decreases much faster so that the zones of decreased velocity are completely joined at 3 d behind this second turbine. The same behavior is shown in [7] for a similar case.…”

“…6e). These have already been observed at a TSR of 5.7 by [7]. In our case they disappear behind the first turbine at half the distance between the two turbines and cannot reach the second turbine, event at this tip speed ratio.…”

A numerical study of the effects of atmospheric and wake turbulence on wind turbine dynamics

“…Recently, Storey et al [32] have two-way coupled an LES solver with the FAST turbine dynamics tool. Their work differs from ours in a few ways.…”

A consistent method for finite volume discretization of body forces on collocated grids applied to flow through an actuator disk

“…In their work, the forces are distributed smoothly to the cells surrounding the rotor through a regularization kernel where the regularization function is a Gaussian. This method is simple to implement and is currently the most widely used in connection with actuator disk/line based methods for simulating wind turbine rotors [10][11][12][13][14][15]. The disadvantage of this method is that it depends on a free parameter, , which controls the amount of smearing.…”