Pre-Analysis & Start-Up
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In the Pre-Analysis & Start-Up step, we'll review the following:
- Theory for Fluid Phase
- Theory for Particle Phase
- Choosing the Cases
Pre-Analysis:
A particle laden flow is a multiphase flow where one phase is the fluid and the other is dispersed particles. Governing equations for both phases are implemented in Fluent. To run a meaningful simulation, a review of the theory is necessary.
Fluid Phase:
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
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
\begin
\rho_f (\frac{d \textbf{u}}
+\textbf
)=- \nabla p + \mu \nabla ^2 \textbf
+ \textbf
\end
-Continuity Equation
\begin
\frac
+ \nabla \cdot (\rho \textbf
)=0
\end
where
$\textbf
$
is the fluid velocity,
the pressure,
the fluid density and
$\textbf
$
is a momentum exchange term due to the presence of particles. When the particle volume fraction and the particle mass loading
are very small, it is legitimate to neglect the effects of the particles on the fluid:
$\textbf
$
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
and
One way-coupling is legitimate here. See ANSYS documentation (16.2) for further details about the momentum exchange term.
Expected Results
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