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UBC Theses and Dissertations

Particle-laden liquid jet impingement on a moving surface Rahmani, Hatef


In the railroad industry, coating of the rail with liquid changes the forces at the wheel-rail interface. Wet leaves on rail tracks can reduce the wheel-rail traction to dangerously low levels. To enhance wheel traction, railroads spray sand on the tracks. The sand may be applied in the form of a particle-laden jet. The impingement of high-speed liquid jets on a moving surface was studied. The jet fluids were dilute suspensions of neutrally buoyant particles in water-glycerin solutions. At the low concentration studied, the suspension has a Newtonian fluid viscosity. A variety of jet and surface velocities, liquid properties, mean particle sizes, and volume fractions were studied. It was observed that for jets with very small particles, the addition of solids to the jet enhances deposition. In contrast, jets with larger particles in suspensions were more prone to splash than single phase jets of the same viscosity. It is speculated that the non-monotonic dependence of the splash threshold on the particle size occurs when the particle diameter is comparable to the lamella thickness. Additionally, volume-of-fluid (VOF) CFD simulations were carried out to provide a full description of the flow field of a particle-free Newtonian jet spreading over a moving surface. The jet Reynolds number and Weber number of the simulations were in the range of 50-1000 and 100-8000, respectively. The simulations were generally in good agreement with experiments and they could successfully predict the lamella dimensions and velocity profiles.

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