Modified liquid transfer model for wet gas-particle systems

Wet gas-particle systems can be found in many industrial applications, including spray coating, granulation and drying. The presence of liquid in a gas-particle system leads to complex behavior due to inhomogeneous liquid distribution and cohesive forces between particles. Through Euler-Lagrange simulations of these flows, one can investigate key physical quantities, such as agglomeration size, liquid distribution, and liquid spreading. However, realistically stiff particles cannot be simulated by Euler-Lagrange simulations due to the small time-step required to resolve collisions between particles. In order to minimize the computational cost, one can reduce the particle stiffness, which allows for bigger time steps. However, it is important to ensure that the flow behavior is not dependent on the chosen stiffness.

In this study, we perform Euler-Lagrange simulations of a wet gas-particle system, allowing for finite rate of liquid transfer between the particles and the liquid bridge (Mohan et al. 2014). We propose a simple scaling correction for the liquid transfer rate based on the ratio between the real and simulated particle stiffness. We first simulate head-on collisions of two particles with different stiffness coefficients without any correction. It is shown that the effective restitution coefficient, which is the ratio of particle velocities before and after collision, is strongly dependent on the stiffness coefficient. After applying the proposed correction, the effective restitution coefficient is independent of the stiffness coefficient. The proposed correction has also been verified in sheared flows and wet gas-solid fluidized beds.