particleSizeDiffSmoothing

Syntax

Defined in couplingProperties dictionary.

smoothingModel particleSizeDiffSmoothing;
particleSizeDiffSmoothingProps
{
    lowerLimit           scalar;
    upperLimit           scalar;
    smoothLength         scalar;
    smoothMagnitude      scalar;
    calcSmoothLenEvery   label;
    writeDiffusionCoeff  Switch;
    verbose              Switch;
}

lowerLimit = scalar fields will be bound to this lower value (default: 1e-12)
upperLimit = scalar fields will be bound to this upper value (default: 1e10)
smoothLength = parameter to determine length scale over which the exchange fields will be smoothed out (default: 5)
smoothMagnitude = parameter to determine diffusion strength for smoothing operations (default: 5)
calcSmoothLenEvery = perform automatic calculation of smoothingLength in this interval of coupling steps (default: 20)
writeDiffusionCoeff = flag for writing of calculated diffusion coefficient (default: false)
verbose = flag for debugging output (default: false)

Examples

particleSizeDiffSmoothingProps
{
    smoothLength     8;
    smoothMagnitude  4;
}

Description

The particleSizeDiffSmoothing model works in a similar manner as the constDiffSmoothing model with the difference that the diffusivity for smoothing operations is not constant but depends on the particle size.

For each cell containing particles, the Sauter diameter

$d_{32} = \frac{\sum d_p^3}{\sum d_p^2}$

is calculated. The Sauter diameter is subsequently smoothed using a diffusion equation with constant diffusivity $D_T = (L \bar{d}_p)^2 / \Delta t$ with $L$ set by the smoothLength model parameter and $\bar{d}_p$ the global arithmetic average of particle diameters. All further smoothing operations are performed by solving a diffusion equation with the diffusion coefficient

$D_S = \frac{(S \hat{d}_{32})^2}{\Delta t}$

based on the smoothed Sauter diameter $\hat{d}_{32}$ and the smoothing magnitude parameter $S$ set by the smoothMagnitude keyword.

The calculation of Sauter diameter and resulting diffusion coefficient is repeated in regular intervals controlled by the calcSmoothLenEvery keyword during the simulation.

Note

This model will reduce the minimum voidfraction setting alphaMin of your voidfraction to yo 0.01.

Model implementation follows the description in [1].

If writeDiffusionCoeff true, the model will write the calculated fields for smoothed Sauter diameter and the resulting diffusion coefficient $D_S$ .

If verbose true, the model will write the reference fields used for the smoothing operations.

Literature

[1] C.-C. Huang, J.A. van Oijen, N.G. Deen, Y. Tang. “A particle-size dependent smoothing scheme for polydisperse Euler-Lagrange simulations”. Chemical Engineering Science 277 (2023): 118765.

Restrictions

This model is tested in a limited number of flow situations.