Comparative study on turbulence models simulating inorganic particle removal in a Pista grit chamber.

Numerical simulations and experimental validations were conducted to determine grit removal efficiency and separation processes for inorganic suspended solids (ISS) with different particle sizes in a vortex-type grit chamber (Pista). The Euler-Lagrange method was used to simulate solid-liquid two-phase flow; the Unsteady Discrete Model was used to simulate the solid phase; and the Renormalization Group k-epsilon (RNG k-ε), Realizable k-epsilon (Real k-ε), and Shear Stress Transmission k-ω (SST k-ω) models were used to simulate the liquid phase. Results of the RNG k-ε model agreed well with the experimental results for particles with d ≤ 200 µm, with an average error of 7.10% (d < 100 µm) and 6.78% (100 µm ≤ d ≤ 200 µm). When particle size exceeded 200 µm, the Real k-ε model had the minimum average error (4.16%). Bed load transport and suspended load transport of the different size ISS particles presented in the grit chamber were important factors influencing grit removal efficiency. Pressure gradient and turbulence intensity distributions simulated by the three turbulence models were significantly different. Particles with diverse sizes reacted distinctly to the disturbance effect caused by pressure difference, which impacted on the accuracy and reliability of simulation results.