Spreading Dynamics and Splatters of Mud Droplets Impinging on Horizontal and Inclined Surfaces

This study examines the spreading process that occurs and the splatter patterns (“fingerprints”) that form when a mud droplet impacts a solid surface at various angles and velocities. The impact velocities of the droplet and the impact angles were between 2.16-7.10 m/s and 15°-90°, respectively. MATLAB software, imaging software, and a high-speed camera were used to analyze the geometric properties of the resulting splatter. The “hat” of the droplet profile closely fit the Beta function during the beginning of the spreading process (t* < 1). When the droplet impacted the surface at a higher impact angle, the lamella expanded in an almost circular fashion (W/L ≈ 1), and the spreading velocity decayed exponentially. By contrast, the aspect ratio decayed with time at lower impact angles. The aspect ratio (W/L) of the elliptic fingerprint of the impact droplet was close to the sine value of the impact angle, and the larger the impact angle, the more splatter patterns (fingerprints) were observed. The Area spreading ratio of the impact droplet on the surface is a function of Weber number and Reynolds number for different solid surfaces.