In the wind farm, there is a regulation when the wind turbine is hoisted. After the top tower is hoisted, the cabin must be hoisted on the same day. What is the reason? I will give you a brief analysis.
Five Ways to Suppress Vortex-Induced Vibration of Towers and Tubes of Wind Turbines
From the point of view of the fluid, any non-streamlined object, at a constant flow rate, alternately creates vortices that detach from the surface of the structure on either side of the object. This alternately issued vortex creates a pulsating pressure on the cylinder that flows in a forward direction and a transverse direction. If the cylinder is elastically supported at this time, or the flexible pipe body is allowed to undergo elastic deformation, the pulsating fluid force will cause periodic vibration of the cylinder (tube body), which in turn will change its tail. The vortex release pattern of the flow. This problem of fluid interaction with structures is referred to as "vortex induced vibration."
If the natural frequency of the tower is close to the frequency of the vortex, the tower will be resonantly destroyed. Therefore, this vortex-induced vibration is extremely harmful, and measures must be taken to prevent it from happening. There are generally five ways to suppress vortex-induced vibration in our wind power industry.
1. Install a spoiler on the tower to suppress vortex-induced vibration
The principle is also relatively simple. The scheme mainly disturbs the wind trajectory by applying a spoiler on the tower, so that it cannot form a frequency stable vortex. Most of the spoilers are made up of a series of triangular columns made of plastic foam. The three spoilers are wound equidistantly in the upper section of the tower, and the bottom is pulled by the string to the ground.
Second, the damper method suppresses vortex-induced vibration
From the characteristics of vortex-induced vibration, the concentrated mass pendulum solution is convenient and effective: as a tuning mass, the pendulum can use the reverse inertial force to significantly suppress the response amplitude of the tower vibration. It should be noted that the mass and the length of the pendulum depend on the mass and stiffness of the tower itself. Therefore, the improper design can not only achieve the vibration damping effect, but also may deteriorate the vibration.
Third, the cable wind rope suppresses the vortex-induced vibration
Simply put, the scheme applies external force through the cable wind rope, destroys the aerodynamic force on both sides of the tower, and limits the displacement amplitude of the initial shaking of the tower, so that the vortex in the free state of the rigid body cannot be generated, thereby suppressing the shimmy, resulting in the tower. The cylinder cannot accumulate the vibration energy generated by the sway during the vortex.
Fourth, the installation of the engine room, generator, impeller to suppress vortex-induced vibration
There are two cases here. After the first nacelle and generator are installed, no matter which angle the wind blows, it will be affected by the engine room and generator to varying degrees, and a stable vortex that causes the resonance of the tower will be discounted. After the second impeller is installed, no matter which angle the wind is blown, it will be affected by the wind turbine blade surface, and the rapid flow field change will make it difficult to form a stable vortex that causes the tower to resonate.
5. When lifting, the tower door is closed, so that the vortex-induced vibration will not increase.
When the bottom of the tower is closed, due to the fluidity and incompressibility of the air itself, the damper effect will be exerted inside the tower, thereby reducing the vibration amplitude of the tower. However, when the bottom part of the tower is opened, the damper composed of air inside the tower loses its effect, so the vibration amplitude of the tower cannot be reduced, and the internal flow of airflow and the external eddy flow have a superposition effect, thereby amplifying The vibration amplitude of the tower.
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