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In the simulations considered for this tutorial, the fluid flow is a 2D perturbed periodic double shear layer as described in the first section. The geometry is Lx = 59.15m, Ly = 59.15m, and the mesh size is chosen as {latex}$\Delta x = L_x / n_x${latex} in order to resolve the smallest vorticies. As a rule of thumb. One typically needs about 20 grid points across the shear layers, where the vorticies are going to develop. The boundary conditions are periodic in the x and y  directions. The fluid phase satisfies the Navier-Stokes Equations:
-Momentum Equations
{latex} 
\begin{eqnarray*}  
\rho_f (\frac{d \textbf{u_f}}{dt}+\textbf{u_f} \cdot \nabla \textbf{u_f})=- \nabla p + \mu \nabla ^2 \textbf{u_f} + \textbf{f}  
\end{eqnarray*}  
{latex}
-Continuity Equation
{latex}  
\begin{align*}  
\frac{\partial \rho_f}{\partial t} + \nabla \cdot (\rho \textbf{vu_f})=0 \\ \Rightarrow \nabla \cdot \textbf{v} = 0 \\ \
\end{align*}  
{latex}


where {latex}$\textbf{u_f}${latex} is the fluid velocity, {latex}$p${latex} the pressure, {latex}$\rho_f${latex} the fluid density and {latex}$\textbf{f}${latex} is a momentum exchange term due to the presence of particles. When the particle volume fraction and the particle mass loading {latex}$M=\phi \rho_p/\rho_f${latex} are very small, it is legitimate to neglect the effects of the particles on the fluid: {latex}\$\textbf{f}${latex} can be set to zero. This type of coupling is called one-way. In these simulations the fluid phase is air, while the dispersed phase is constituted of about 400 glass beads of diameter a few dozens of micron. This satises both conditions {latex}$\phi \ll 1${latex} and {latex}$M \ll 1${latex}
One way-coupling is legitimate here. See ANSYS documentation (link) for further details about the momentum exchange term.