Nanoparticle behaviour in multiphase turbulent channel flow

Abstract The behaviour of dispersed nanoparticles within a turbulent wall-bounded flow is investigated, with the fluid phase properties chosen to represent a thermofluid flow typical of those present in solar thermal power plants. The continuous phase is modelled using direct numerical simulation with the open source spectral element-based solver, Nek5000, with predictions of a statistically steady turbulent channel flow at shear Reynolds number Reτ = 180 first obtained and validated. A Lagrangian particle tracking routine is subsequently implemented to simulate the dispersed phase, and is capable of accommodating one-, two- and four-way coupling between the fluid and discrete phases. In order to investigate the effect that the turbulence field has on the dispersion properties of the solid nano-particulate phase, mean fluid and particle velocities, and turbulence statistics, are obtained and presented. Particle mean velocities are observed to lag behind the fluid flow in the outer layer for all coupling methods. Particle streamwise velocity fluctuations are lower than those of the fluid in the bulk region of the flow, but are greater than the latter in the buffer layer, with the addition of particle agglomeration augmenting this effect. Particle concentrations in the near-wall region are observed to increase over time due to turbophoresis.