Two phenomena occur as the high-speed droplet impacts the solid surface, namely, high pressures are generated at the point of impact and fluids flow radially along the solid surface from the impact point (the center). Different energy distribution patterns are seen in spheres or cubes, hitting the target surface obliquely, because more energy has left with the particles and the distribution proportion has been changed. Almost 80% of the total energy consumed by the material is thermally dissipated, whereas about 10% is stored in the material with the generation of dislocation and other crystal defects. After vertically hitting the target, the sphere maintains only 1%–10% of its initial energy, and the rest is dissipated over the material surface, including a significant loss due to elastic waves (1%–5%) and plastic indentation (about 90%), which has nothing to do with erosion. An energy distribution schematic is shown in Fig. 1.21. Grant, Head, Harry, and Hutchings have discussed the energy exchange that occurs as the spheres or cubes hit the surface at an incident angle of either 30 or 90 degrees, to estimate the initial kinetic energy dissipation of the particles at the moment of the impact ( Dick et al., 1995). In other words, energy will be redistributed between both objects, and the impacted surface may suffer from elastic or plastic deformation ( Jiajun, 1992 ). The energy exchange occurs as the particle hits the solid surface. In a broad sense, the particle can include solids, liquids, and gas bubbles. Įrosion refers to the damage on the material surface caused by the impact of the particle. Smaller incident angle results in more backscatter, although for very rough surfaces the backscatter is independent of θ. In general, reflectivity from distributed scatter decreases with increasing incident angles. This in turn causes variations in pixel brightness. A local incident angle could be determined for any pixel in the radar data. On a flat surface, incident angle is the complement of the depression angle ( Fig. The incident angle helps determine the target appearing in an image. Incident angle is the angle between the radar beam and a target object. The depression angle decreases outward from near to far range. The incidence angle at any point within the range is the angle between the radar beam direction (of look) and a line perpendicular (normal) to the surface, which can be inclined at any angle (varies with slope orientation in non-flat topography). ![]() Incident angle θ is a major factor influencing the radar backscatter and the targets appearing in the images.
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