23.2.4 Drag Laws

There are eight drag laws for the particles that can be selected from the Drag Law drop-down list under Drag Parameters.

The spherical, nonspherical, Stokes-Cunningham, and high-Mach-number laws described in this section in the separate Theory Guide are always available, and the dynamic-drag law described in this section in the separate Theory Guide is available only when one of the droplet breakup models is used in conjunction with unsteady tracking. See Section  23.2.6 for information about enabling the droplet breakup models. The remaining three, Wen-Yu, Gidaspow, and Syamlal-OBrien are available only when the dense discrete phase model is enabled (Section  24.5.7) and the flow regime consists of a dense gas-solid. However, with these models, you cannot verify up front whether it really is a dense flow or a gas-solid flow indeed. It is up to you to decide. In any case, these drag formulations are suitable for dense gas-solid flows.

If the spherical, high-Mach-number, dynamic-drag, Wen-Yu, Gidaspow, or Syamlal-OBrien drag law is selected, no further inputs are required. If the nonspherical law is selected, the particle Shape Factor ( $\phi$ in this equation in the separate Theory Guide) must be specified. The shape factor value cannot exceed 1. For the Stokes-Cunningham law, the Cunningham Correction factor ( $C_c$ in this equation in the separate Theory Guide) must be specified.