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Full scale train underbody aerodynamic evaluation for top of rail friction modifier application Mulligan, Quinn Alexander

Abstract

Liquid jet impingement is employed in the rail industry to apply friction modifier to the rail surface. Use of the friction modifier is known to reduce wear and improve fuel efficiency. L.B. Foster ® deploys friction modifier using a nozzle located downwind of the wheels on freight trains. Understanding the aerodynamic environment of the nozzle is important for researching how to maximize the deposition of the liquid friction modifier from the nozzle to the tracks. The air pressure and velocity at the location of the nozzle was evaluated experimentally at full scale in field trials. The pressure at a fixed ground location was measured by transducers as the train passed. The air velocity in the reference frame of the moving vehicle was measured using a fiber-film anemometer at the location of the liquid-friction-modifier spray nozzle, 0.4 wheel diameters downwind of the wheel center. The measured air speeds scales linearly with the train speed, and the measured pressure scales linearly with the dynamic pressure, implying that Reynolds number effects are negligible. The pressure distribution showed an initial pressure increase just downwind of the leading edge of the vehicle followed by a spike in suction. The pressure distribution was found to depend on the orientation of the vehicle. With a rail car leading the vehicle, the spike in suction produced was about 50% larger than the suction spike produced when a locomotive, lower to the ground, was leading the vehicle. The mean air speed was measured to be approximately 29% of the train speed. The mean air speed the same distance upwind of the wheel was measured to be approximately 38% of the train speed. Turbulence intensity levels were measured to be about 0.15. Cross wind effects became much less significant when the train speed was equal to or greater than the cross wind speed. The train undercarriage airflow was modeled numerically using Autodesk Simulation CFD™ software. The CFD simulations were in approximate agreement (typically, within 2%) with experimental measurements and confirmed that the presence of the support bracket for the anemometer had limited impact on the measured wind speed.

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