Experimental study of contact velocity effect on spreading factor of non-Newtonian and Newtonian droplets during collision with dry solid surface

The collision of droplets on solid surfaces is widely used in oil and gas industry, surface painting, hot surface cooling and spraying of agricultural products. In the present study, the spreading factor of Boger non-Newtonian fluid is experimentally investigated on the dry solid surface such as an acrylic (Plexiglas) and stainless steel sheet and is compared with Newtonian droplets (water and glycerin). The plates of Plexiglas and stainless steel both have a hydrophilic surface. In this research, the Newtonian and non-Newtonian fluids droplets collapse at two heights of 27 and 47 cm from the dry solid surface and are examined in the range of Weber numbers 245≤We≤"538" . The purpose of this study is to investigate the effects of contact velocity on the spreading factor of non-Newtonian and Newtonian droplets during the collision. The results of this study show that with the growth of Weber number (increasing contact velocity), the maximum value and velocity of spreading and receding are increased for the Newtonian or non-Newtonian droplets. Also, with increasing the viscosity of droplets, the value and velocity of spreading and receding are decreased for the Newtonian and non-Newtonian droplets. By increasing the velocity of collision on the Plexiglasas surface (raising the Weber number) up to 32%, the maximum value of droplets spreading is increased 22, 31 and 20 percentage respectively for the fluids of Boger, water and glycerin.