Everybody feels the special hot weather and the forecasts tell us it will be warmer in the upcoming weeks. However, do not forget that winter is coming as usual, and you have also to tide up your weather-sensitive system such as a wind turbine.
Wind turbine was developed to overcome our climate-changing issues, but during the transition phases the turbine itself undergoes with some challenged situations such as winter and the worst-case scenario is ice accumulation over the blades of the wind turbine.
The questions now are ‘Why this is the worst-case scenario’’ and the second one is ‘How to mitigate the physical problem due to ice-accumulation over blades’’.
Icing and Wind Turbine
The main issue due to ice building up is the total changing of the wind turbine properties, the most important physics here are the aerodynamics forces over the blades which will be inevitably changed due to the creation of ice as it will be discussed later, not only limited to the aerodynamics forces.
However, the mass will be changed and therefore, we issue new parameters such as natural frequencies and the vibration amplitudes. Ice effects on the vibration frequencies of the system because when an additional mass is added to the blades, the natural frequency will be changed such as illustrated in Figure 2 ‘pendulum natural frequency & mass’.
If the natural frequency of blades just meets the vibration frequency of the system,the resonance phenomena will be occurred, and I think no one would like to live this scenario in a cold weather.
Furthermore, the same collapsing will be happened due to the changing of aerodynamics forces, because of the stall phenomena.
Stall is the most critical phenomena can be occurred in aerodynamics, the meaning of stall is that “air is not attached to the blades anymore”, that means there is separation areas beyond the trailing edge of the blades and leads to unsteadiness airflow cause heavy-weighted drag force towards the blads.
SIMULIA & Wind Turbine
Let’s take a journey with the SIMULIA brand from Dassault Systèmes in how to overcome all the physical problems related to the ice-accumulation with Wind Turbine design.
First, we must take the aerodynamic characteristics into consideration in the stage of design and validation, we have also to add a model of icing. And this is the tricky point of the ice model. And here we are going we our software (PowerFlow).
PowerFlow is a robust CFD software based on the Lattice-Boltzmann Method (LBM) which is a highlighted method in research communities because of the less computing time compared to the conventional CFD method (RANS) models.
Furthermore, there are plenty game changers concerns with Power Flow:-
Due to the dependency on LBM, there is independence on the PDEs on your governing equations, that means low BCs sensitivity compared to RANS method. Also the unsteadiness theory beyond this method makes the Power Flow robust solver and reliable in the transient cases and fully transient cases.
And at the POV of Ice-building, PowerFlow has the most sophisticated engineering-modeling technology which is ‘models for Ice’ such as following figure shows.
The second physics we have due to Ice is vibration and mass balance analysis so in SIMULIA we have Simpack software which is used to analysis the multi-body dynamics and rotating parts together, in the case of Iced wind turbine we must calculate the vibration amplitudes and natural frequencies of wind turbine toavoid the undesired physical phenomena.
References:
1- Dassault Systèmes “5TH WIND AND DRIVETRAIN CONFERENCE”
2- Dassault Systèmes “How Simulation Can Help Winterize Wind Turbines”
