We are developing numerical techniques to simulate wind turbines using high-order h/p methods. In our solver, HORSES3D, we have implemented actuator discs, actuator lines, immersed boundaries, and sliding meshes. These techniques vary in complexity, accuracy, and computational cost (see figure below).
Actuator lines enable the explicit modelling of blade motion while keeping computational costs low (since blades are represented by distributed point forces).
When comparing to experimental data, our actuator line results show good agreement, but it is necessary to include the tower and nacelle, see figure on the right. In this case, the latter are simulated using immersed boundaries, while the rotating turbines use actuator lines specifically adapted to high-order solvers.
When using P7 (and a total number of 37M dofs) the wake is highly accurate and comprable to low order methods that use 3 times more dofs.
Using high-order methods, we can fix the number of elements (the h-mesh) and vary the polynomial order (P) in each element. Without re-meshing, we can increase the resolution of the simulation by changing the polynomial order in the control file before simulating. In addition, increasing the polynomial order is much more accurate and efficient than increasing the number of elements, as an exponential decay of the error can be achieved using high-order polynomials, see figure on the right.
Horses3d can now simulate offshore wind turbines including air water interfaces.
