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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
Unknown macro: {latex} $\Delta x = L_x / n_x$
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
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\begin
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\rho_f (\frac{d \textbf{u_f}}
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+\textbf
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)=- \nabla p + \mu \nabla ^2 \textbf
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+ \textbf
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\end
-Continuity Equation
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\begin
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\frac
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+ \nabla \cdot (\rho \textbf
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\Rightarrow \nabla \cdot \textbf
\Rightarrow \nabla \cdot \textbf
= 0
\end
where
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$\textbf
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$
is the fluid velocity,
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the pressure,
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the fluid density and
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$\textbf
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$
is a momentum exchange term due to the presence of particles. When the particle volume fraction and the particle mass loading
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are very small, it is legitimate to neglect the effects of the particles on the fluid:
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\$\textbf
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$
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
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and
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One way-coupling is legitimate here. See ANSYS documentation (link) for further details about the momentum exchange term.
One way-coupling is legitimate here. See ANSYS documentation (16.2) for further details about the momentum exchange term.
Expected Results
Under Construction
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