Validation case study: sound waves in a fluidized medium

Abstract In this chapter, the speed of sound waves is investigated in more detail using CFD-DEM numerical simulations. The idea of establishing standing waves in a two-phase medium as reported by Roy et al. was employed. Appropriate initial and boundary conditions were applied in the CFD-DEM simulation to capture the phenomenon. The effect of varying the height of the bed was also investigated. The results of the simulations matched those from literature, giving a speed of sound in the two-phase medium very close to that of the expression of Roy et al. The simulations allowed details of the fluctuations in the pressure, gas velocity, and particle velocity to be studied. Functions (based on a damped standing wave) were fitted to these fluctuations, which allowed their evolution in time and space to be described. These fitted functions were substituted to the linearized governing equations for two-phase flow. Using these assumed solutions allowed a new relationship for speed of sound and damping in the system to be derived. It was concluded that the damping in the system is due to the effective bulk viscosity of the solid phase, which arises from the particle contacts.