PSI - Issue 52

Quaiyum M. Ansari et al. / Procedia Structural Integrity 52 (2024) 122–132 2 Quaiyum M. Ansari/ Fernando Sánchez/Luis Doménech-Ballester/ Trevor M. Young/ Structural Integrity Procedia 00 (2019) 000 – 000 1. Introduction Wind energy plays a crucial role in generating green energy and reducing the carbon emission footprint in the environment. There is a global and regional demand global demand for reduced greenhouse gas emissions which is growing day by day. Ireland has set its ambitious climate action plan for 2023 to halve emissions by 2030 and reach a net zero or carbon-free country no later than 2050 [1]. Wind turbine (WT) blade size is also increasing to increase the power capacity[2]. Keegan et al. [3] discuss the typical rain erosion issue of coating on WT blades. Rain erosion of the Leading Edge Protection (LEP) of wind turbine blades is a major concern that affects continuous power generation and increases maintenance and downtime. When raindrops hit the LEP system, they can cause debonding and delamination of the coating and substrate [4]. Rain erosion testing is typically performed using either a whirling arm [5, 6] or a jet [7, 8, 9]. Cook [10] investigated erosion by water hammer. He discovered that erosion is caused by water hammer effects caused by cavitation. The formation and collapse of cavities in the water cause the water hammer to intensify. Bowden and Field [11] investigated brittle fractures of solids caused by liquid, solid and shock. They investigated the stress pulse caused by high velocity impact on water droplets on solid surfaces and discovered that high velocity liquid impact creates a sharp pulse-like detonation against the surface. The inability of liquid to flow at the early stages of the impact causes compressible liquid behaviour. Huang et al. [12] performed high-velocity impact on hydrodynamic phenomena. They studied the dynamics of compressible water droplet impact on a rigid solid surface analytically. They discovered that the maximum pressure calculated in a one-dimensional problem is greater than the maximum pressure calculated in a two-dimensional problem. Haller et al. [13] studied the dynamics of high-velocity, small-droplet impact on a rigid surface. During the collision, the shock wave was observed to be generated at the contact edge. The liquid zone near the target is highly compressed, resulting in the generation of wave envelopes. Hinkle [14] studied the kinetic energy and momentum of the water droplet. They discovered that the change in water droplet momentum perpendicular to a dry and smooth surface is caused by equal and opposite forces between the water and the plate. Imeson et al. [15] used a piezoelectric transducer to measure the impact force of water droplets. They discovered that while it is possible to express impact force in terms of kinetic energy or peak voltage, it is not possible to calculate momentum due to droplet size changes. Li et al. [16] studied the low velocity impact of a water droplet on a solid surface and found that the water droplet impact differs from the solid impact. The peak frequency in water droplet impact is in the low frequency zone, whereas solid ball impact has no such frequency other than the plate frequency, which also exists in water droplet impact. Furthermore, the duration of the impact increases as the droplet size increases. Gunn and Kinzer [17] calculated the terminal velocity of 1500 water droplets in stagnant air ranging in mass from 0.2 to 100,000 micrograms. Each determination was found to be moderately accurate. 123

Fig. 1. Rain erosion of the leading edge of wind turbine blades [18] Figure (1) depicts typical rain erosion [18]. Katsivalis et al. [19] recently performed mechanical and interfacial characterization of the LEP system. They tested rain erosion on various LEP systems using the WARER (Whirling Arm Rain Erosion Rig). The typical rain erosion sample and its CT scan are shown in Fig. (2) [19]. They discovered

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