Numerical simulation of bubble columns: LES turbulence model and interphase forces blending approach

In this study the Large Eddy Simulation (LES) turbulence approach was adopted to simulate bubble columns in a wide range of gas velocity and operating conditions, in order to obtain a general model capable of simulating with satisfactory accuracy and moderate computational resources most industrial cases. The model used to carried out the numerical simulations stems on the Eulerian-Eulerian two-fluid model. A particular feature of the model is the implementation of a blending approach, which is adopted to describe the phase inversion at the surface of the gas-liquid mixture. An extended investigation of the main LES turbulence models was conducted at high gas velocity to find the most suitable one for the investigated test cases: the Smagorinsky model accounting also for the bubble induced turbulence provided the most notable results in a wide range of operating conditions. The validity of the model was also confirmed at lower gas velocity. A comparison with the standard k-ɛ RANS model showed that the LES methods produced significantly more accurate results, in particular for systems with non-symmetrical gas feed, even though the computational time required is marginally higher.