If the discrete phase interacts (i.e., exchanges mass, momentum, and/or energy) with the continuous phase, you should enable the Interaction with the Continuous Phase option. An input for the Number of Continuous Phase Iterations per DPM Iteration will appear, which allows you to control the frequency at which the particles are tracked and the DPM sources are updated.
For steady-state simulations, increasing the Number of Continuous Phase Iterations per DPM Iteration will increase stability but require more iterations to converge. Figure 22.11.1 shows how the source term, , when applied to the flow equations, changes with the number of updates for varying under-relaxation factors. In Figure 22.11.1, is the final source term for which a value is reached after a certain number of updates and is the initial source term at the start of the computation. The value of is typically zero at the beginning of the calculation.
In addition, another option exists which allows you to control the numerical treatment of the source terms and how they are applied to the continuous phase equations. Update DPM Sources Every Flow Iteration is recommended when doing unsteady simulations; at every DPM Iteration, the particle source terms are recalculated. The source terms applied to the continuous phase equations transition to the new values every flow iteration based on Equations 22.9-6 to 22.9-8. This process is controlled by the under-relaxation factor, specified in the Solution Controls panel, see Section 22.15.2.
Figure 22.11.1 can be applied to this option as well. Keep in mind that the DPM source terms are updated every continuous flow iteration.