External Force Model: Viscous Field

This model is used to predict influence of gas/fluid phase on particle motion.

Re=\frac{2 \cdot R_p \cdot |\vec{v}_{p}|}{\nu_f}

C_D = \begin{cases}
\frac{24}{Re} & \text{if } Re < 0.5 \\
\frac{27}{Re^{0.8}} & \text{if } 0.5 < Re < 10.1 \\ 
\frac{17}{Re^{0.6}} & \text{if } Re > 10.1 \end{cases} 

The drag force $F_D$ acts in the direction opposite to the particle velocity $v_p$.

F_D = \frac{\vec{v}_{p}}{|\vec{v}_{p}|} \cdot {|\vec{v}_{p}|}^2 \cdot \pi \cdot {R_p}^2 \cdot \frac{\rho_g}{2} \cdot C_D

---

Model Parameters

• MEDIUM_VISCOSITY - Dynamic viscosity of the fluid $\nu_f$.
• MEDIUM_DENSITY - Density of the fluid $\rho_f$.

---

Symbols

Symbol	Description
$Re$	Reynolds number $[-]$
$R_p$	Particle radius $[m]$
$v_p$	Particle velocity $[m/s]$
$\rho_f$	Density of the fluid $[mg/m^3]$
$\nu_f$	Dynamic viscosity of the fluid $[m^2/s]$