Fuel Saturation Distribution Model Reference

Before fuel droplets evaporate and mix homogeneously throughout a cell, the evaporated fuel is initially located in close proximity to the fuel droplets. The Fuel Saturation Distribution model uses a fuel mass fraction profile to account for the initially uneven distribution of fuel mass fraction in a cell.

Table 1. Fuel Saturation Distribution Model Reference
Theory	See Fuel Saturation Distribution.
Provided By	In-Cylinder > Models > Optional Models
Example Node Path	Continua > Physics 1 > Models > Fuel Saturation Distribution
Requires	Using Simcenter STAR-CCM+ In-cylinder, with Auto-select recommended models activated: In-Cylinder Optional Models: Combustion In-Cylinder Combustion Model: ECFM-3Z or ECFM-CLEH In-Cylinder Optional Models: Injection In-Cylinder Ignition Model: Auto Ignition See Accessing Simcenter STAR-CCM+ In-cylinder
Properties	Key properties are: First Zone Saturation Profile Coefficient and Second Zone Saturation Profile Coefficient. See Fuel Saturation Distribution Properties.
Activates	Solvers	Fuel Saturation Distribution. See Solvers.
	Monitors	ZfumSatScalar and ZspumSatScalar.
	Field Functions	Fuel Saturation Mass Fraction, Mean Cell Droplet Temperature, ZfumSatScalar, and ZspumSatScalar. See Field Functions.

Fuel Saturation Distribution Model Properties

Convection

In transport equations, you can choose from a range of schemes that calculate the convection term at a cell face. This calculation requires Simcenter STAR-CCM+ to compute the face value of a quantity from the surrounding cell values. The method used for computing this face value has a profound effect on the stability and accuracy of the numerical scheme. For guidance on selecting a convection scheme, see Convective Flux.

1st-order: First-order convection scheme.
2nd-order: Second-order convection scheme.

Secondary Gradients

Neglect or include the boundary secondary gradients for diffusion and/or the interior secondary gradients at mesh faces.

On: Default value. Solves for interior and boundary types of secondary gradient.
Off: Does not solve for either type of secondary gradient.
Interior Only: Solves for the interior secondary gradients only.
Boundaries Only: Solves for the boundary secondary gradients only.

Flow Boundary Diffusion

When activated, this property includes the flow-boundary diffusion fluxes (or viscous fluxes for flow models) as given by Eqn. (899). This property is activated by default.

First Zone Saturation Profile Coefficient

K_{f u m}

in Eqn. (3953).

Second Zone Saturation Profile Coefficient

K_{s p u m}

in Eqn. (3951).

Fuel Saturation Distribution Solver Properties

Under-Relaxation Factor: In order to promote convergence, this property is used to under-relax changes of the solution during the iterative process. If residuals show solution divergence or do not decrease, reduce the under-relaxation factor.
Verbosity: Allows you to choose how much information Simcenter STAR-CCM+ reports in the Output window while the simulation is running. This property is useful for debugging problems when they occur. The available options are None, Low, and High.
Solver Frozen: When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.
Reconstruction Frozen: When On, Simcenter STAR-CCM+ does not update reconstruction gradients with each iteration, but rather uses gradients from the last iteration in which they were updated. Activate Temporary Storage Retained in conjunction with this property. This property is Off by default.
Reconstruction Zeroed: When On, the solver sets reconstruction gradients to zero at the next iteration. This action means that face values used for upwinding (Eqn. (905)) and for computing cell gradients (Eqn. (917) and Eqn. (918)) become first-order estimates. This property is Off by default. If you turn this property Off after having it On, the solver recomputes the gradients on the next iteration.
Temporary Storage Retained: When On, Simcenter STAR-CCM+ retains additional field data that the solver generates during an iteration. The particular data retained depends on the solver, and becomes available as field functions during subsequent iterations. Off by default.

Field Functions

Fuel Saturation Mass Fraction: The mean cell fuel mass fraction at saturation ${\tilde{Y}}_{F S}$ in Eqn. (3955)—which typically corresponds to the cell average fuel mass fraction at the surface of the droplets.
Mean Cell Droplet Temperature: The average temperature of the droplets in a cell.
ZfumSatScalar: The transported relaxed total unburnt fuel mass fraction from the first zone. ${\tilde{Z}}_{F U M}$ in Eqn. (3950).
ZspumSatScalar: The transported relaxed total unburnt fuel mass fraction from the second zone. ${\tilde{Z}}_{S P U M}$ in Eqn. (3949).