Discrete Phase Model (DPM): Tips

Tips About DPM

• To simulate the evaporation process of droplets, we need to define the thermophysical properties of Material accurately. Saturation vapor pressure, Binary diffusivity, latent heat, boiling point, and specific heat should be considered. These parameters are accessible in the Materials section(check the figure below). Notice that the droplet’s evaporation temperature should be higher than the particle’s injection temperature. So the temperature of particles must reach the evaporation temperature firstly to start vaporizing.

• To control the instability of the solution, we need to define proper under-relaxation factors located in the Solution=> Control part(figure below). Default values are acceptable in most cases unless the solution becomes unstable and doesn’t reach a satisfying convergence. It means the residuals should be less than 10e-3 except for energy, radiation, and mixture fraction that should be less than 10e-6. It is recommended to start the calculation by default values, and if the solution becomes unstable, lower the values and continue the calculation. In addition, it is better not just to follow the residual values but to monitor variables of interest.

• The convergence problem is mainly caused by high source terms generated in cells. This can be solved by using the node-based averaging method or trying source term linearization. The linearization process for momentum, energy, and species is boosted by activating Linearize Source Terms in the Numerics Furthermore, if there is no mass transfer, it can be used along with Node Based Averaging; It spreads a load of DPM source into neighboring cells by collecting data on mesh nodes. As a result, it reduces grid dependency and improves convergence in steady-state simulations. These items can be seen in the figure below.