Numerical Simulation on the Influences of Wind Pressure on Jet Characteristics of Shotcrete

Abstract

A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding with a wall based on computational fluid dynamics theory, in which concrete was regarded as a Bingham fluid. The influences of wind pressures、 pumping speeds、 air incident angles and rheological parameters on five characteristic parameters including spouting velocity, jet velocity, jet trajectory, collision velocity and distribution of shotcrete on the wall were analyzed in depth. Results showed that concrete was gradually mixed well with air in the nozzle with an increasing average velocity, and the increase of velocity was most pronounced in the contraction section of nozzle. With the increases of wind pressures and pumping speeds, the spouting velocity and spouting mass of concrete both increased. Higher wind pressure and pumping speed led to larger jet velocity and more concentrated distribution, resulting in significantly longer jet distance, higher collision velocity and larger distribution area. The collision velocity and volume fraction of concrete on the wall were distributed symmetrically along Y axis, shifting towards the direction of gravity. With the increases of air incident angles, the spouting velocity and spouting mass of concrete both decreased, the shifting to gravity is weakened and the volume fraction decreased first and then increased. When plastic viscosity decreased, the spouting velocity and spouting mass of concrete both increased, accompanying with a higher jet velocity, a longer spraying distance and a larger distribution area.

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