| Summary: | In the railroad industry a friction modifying agent may be applied to the rail or to the wheel in the form of a liquid jet. In this mode of application the interaction between the high speed liquid jet and a fast moving surface is important. Seven different Newtonian liquids with widely varying shear viscosities along with twelve different solutions of polyethylenoxide (PEO) and water with varying relaxation times were tested to isolate the effect of viscosity and elasticity from other fluid properties. Tests for the Newtonian liquids were done with five surfaces having different roughness heights to investigate the effects of surface roughness. High speed video imaging was employed to scrutinize the interaction between the impacting jet and the moving surface. For both Newtonian and Elastic liquids and all surfaces, decreasing the Reynolds number reduced the incidence of splash and consequently enhanced the transfer efficiency. At the elevated Weber numbers of the testing, the Weber number had a much smaller impact on splash than did the Reynolds number. The ratio of the surface velocity to the jet velocity has only a small effect on the splash, whereas increasing the roughness-height-to-jet-diameter ratio substantially decreased the splash threshold. Moreover, the Deborah number was also salient to the splash of elastic liquids.
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