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Water droplet erosion (WDE) is a complex phenomenon that has been investigated for nearly a century. This form of erosion affects a wide range of energy industries from steam turbines and natural gas pipelines to wind turbine blades. The moving droplets impacting at a high relative speed create a high surge in surface pressure on the impacted material and damage the surface. The damage removes materials and can compromise strength for steam turbines and pipelines or affect the lift and drag forces on wind turbine blades. Research on WDE has been ongoing for decades with a majority of the reported results focused on metallic material testing and qualitative analysis comparing methodologies or surface conditions. The ongoing research at The University of Tulsa is conducting experiments with a variety of materials while exposed to an environment where water droplet erosion occurs. Impact velocity and droplet sizes are controlled within the facility and ongoing research with particle image velocimetry (PIV) is in use to characterize the falling droplets. Stainless steel 316, Aluminum 6061, and a variety of non-metallic materials are tested for a variety of conditions. The mass of each specimen is tracked and recorded at set intervals to determine the erosion ratio and erosion rate. Various other factors such as flowrate and rotational velocity are determined before testing as well as the percentage of droplets which impact the surface is determined with the use of a high-speed camera. Scanning electron microscopy (SEM) is also utilized to examine the material’s surfaces before and after testing to investigate the severity of erosion by water droplets. One impact velocity and one impact angle are set for all tested materials. These data points will be the starting point for future tests and modeling work to predict water droplet erosion based on simple factors. 

Liquid droplet impact is a subject that has been investigated in both engineering and non-engineering applications to understand and to control this phenomenon. Spray cooling, ink-jet printing, spray coating and painting, soil erosion prevention, pesticide application, and impact erosion are merely a few examples in which droplet impact is involved. Erosion caused by droplet impact on a solid surface is important in numerous elements of industrial equipment, such as pipelines, steam turbines, and wind turbine blades. Though experimental and modeling studies have been performed on this topic, most failed to perform quantitative investigation especially when it came to the erosion of wind turbine blades. Moreover, most approaches assume that the impacting droplets are completely spherical and unaffected by any local turbulence or vortex shedding. As the droplet erosion process could be affected by several parameters, such as the impact velocity, shape and size of the droplets, this study focuses on investigating droplet properties and movement in a controlled lab environment. High speed imaging and Particle Image Velocimetry (PIV) methods are used for this purpose. PIV is used to measure the velocity, circularity, and size of the falling droplets in both disturbed and un-disturbed flow conditions. High-speed camera imaging provides additional insight to the path of the droplets’ movement in the presence of any turbulence. Experiments are performed at a variety of flow rates utilizing a range of blunt needle gauge sizes to create different droplet sizes. It is observed that the blunt needles produce a train of droplets that are different in size following each leading droplet. This is a crucial observation as it will have a direct impact on the magnitude of erosion and should be considered in the future modeling efforts.