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Fibre behaviour in the spunbonding process. Part II: Modelling fibre dynamics in the diffuser

The behaviour of a fibre subject to the turbulent air flow in the diffuser in the spunbonding process is studied using a three-dimensional dynamics model in which the fibre is discretised as a chain of beads connected by linear and rotational springs. The turbulent air drag acting on the fibre is modelled as a random force, as a function of the mean air velocity, the turbulence intensity, and the spectrum of turbulence. The effect of the air flow parameters and the fibre diameter on the amplitude and the frequency of the fibre oscillations is analysed to understand how the fibre position at the exit of the diffuser is controlled by the turbulent air flow in spunbonding. This in turn will affect fibre laydown and the associated web formation.