7. Direct Numerical Simulation of Bi-Disperse Particle-Laden Gravity Currents on Lock-Exchange Configuration with Different Schmidt Number

We performed direct numerical simulations (DNS) of bi-disperse particle-laden gravity currents on a lock-exchange configuration with different values of Schmidt number (\(\mathrm{Sc}\)) for each particle fraction, to investigate the impact of double mass diffusivity on flow dynamics and deposition. We used the high-order code Incompact3d to solve the incompressible Navier–Stokes equations and the scalar transport equation. We compared our results with previous physical and numerical experiments available in the bibliography, obtaining a good agreement. We simulated two cases: (i) \(\mathrm{Sc}=1\) for both particle fractions and (ii) \(\mathrm{Sc}=3\) and \(\mathrm{Sc}=1\), for coarse and fine fraction, respectively. Case (ii) shows higher reduction of the front velocity of current during the deceleration phase. For case (i), the current has higher amount of suspended fine particle during all the experiments, which could explain why the front velocity has lesser decreasing during the deceleration phase. The configuration of the final deposit profile shows that case (ii) has the highest deposit peak nearer to the lock-exchange gate than the case (i). We also calculated the temporal evolution of the energy budget of our simulations, and we find that the energy is conserved during all time of our simulations and the term related to turbulent dissipation is the principal responsible for energy loss.