Simulation of Fully Resolved Particle-Particle Interactions in Turbulence with Behavioural Modification

Fully resolved particle-particle interaction events in turbulence are studied using high fidelity simulation. The continuous phase uses a spectral element-based direct numerical simulation and the discrete phase is modelled using the immersed boundary method. The ghost-cell technique is used to achieve particle-fluid coupling and the method is validated against empirically determined drag coefficients with strong agreement for high resolution particle meshes. The interactions take place in an isotropic box of turbulence at Reynolds number (based on the Taylor

microscale), = 51 . This value is selected to closely resemble those typical of the buffer layer in a turbulent channel flow at shear Reynolds number, = 180. Particulate phase properties are chosen to represent 100 diameter calcite particles in water, but the chemical and dynamic properties of both phases are varied to determine the extent of behavioural modification through alteration of these parameters. Results indicate that the restitution coefficient has the greatest effect on collision dynamics, with an increase leading to fewer particle agglomerations.

Reducing the Hamaker constant has a lesser effect on the resulting interaction but does lower the mean speed of the particles undergoing collision. The electric double layer potential has very little effect on any of the agglomeration dynamics, since its strength and effective range is much lower than that of the van der Waals component. Suggestions are offered for behavioural modification techniques based on the present results.