Soot Sections Model Reference

Table 1. Soot Sections Model Reference

Theory

See Soot Sections.

Provided By

In Simcenter STAR-CCM+: [physics continuum] > Models > Soot Emissions Model

Example Node Path

Continua > Physics 1 > Models > Soot Sections

Requires

STAR-CCM+ In-cylinder: Optional Models: Combustion; Combustion Model: Complex Chemistry, ECFM-3Z, or ECFM-CLEH

Simcenter STAR-CCM+: Material: Multi-Component Gas; Reaction Regime: Reacting

Then either:


Reacting Flow Models: Reacting Species Transport Reacting Species Models: Complex Chemistry	Reacting Flow Models: Flamelet Flamelet Models: Flamelet Generated Manifold (FGM) or Steady Laminar Flamelet

and:

Optional Models: Soot Emissions

Properties

Key properties are: Convection, Source Enabled Trigger, Begin, Secondary Gradients, and Flow Boundary Diffusion. See Soot Sections Properties.

Activates

Model Controls (child nodes)

Soot and Soot Model Properties.

Other nodes

[physics continuum] > ECFM Soot Table Generator

Appears when using one of the ECFM models.

See Table Generators Reference.

When using the Complex Chemistry model, the soot species are contained within the mechanism.

Solvers

Soot. See Solvers.

Monitors

SootSection[n]

Report Options

Soot PSDF, Soot, Sections Diameters, Soot Plots, Soot Particle Size Distribution. See Reports.

Field Functions

Soot Mass Density, Soot Mass Fraction Sec[n], Soot Mean Diameter, Soot Nucleation Rate, Soot Number Density, Soot PSDF Sec[n], Soot Total Mass Fraction, Soot Volume Fraction, Steric Factor. See Field Functions.

Tables

Soot Sectional Particle Size Distribution Table - Boundaries, Soot Sectional Particle Size Distribution Table - Regions

Soot Sections 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.

Source Enabled Trigger

Controls whether Simcenter STAR-CCM+ starts calculating the chemistry at the time-step, iteration, or physical time that you specify in the Begin property, or whether this model never contributes any sources.

Begin

Specifies the iteration, time-step, or physical time after which the reactions are activated. Before this iteration, time-step, or physical time, reactions are deactivated. Specifying a physical time [degCA] allows you to activate chemistry sources just before spark ignition. When specifying it as an expression which varies during the simulation, reactions are only active when the current iteration, time-step, or physical time is higher than the value provided by the expression.

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.

Soot 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.
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.

Reports


Reports	With Complex Chemistry	With ECFM Models	With Flamelet Models	With Reactor Network
Soot PSDF A sum report of the soot particle size distribution function $\frac{d N}{d \log (d_{p})} (i)$ .
Soot Sections Diameters Mean diameter of each soot section.
Reactor Network Soot PSDF A sum report of the soot particle size distribution function $\frac{d N}{d \log (d_{p})} (i)$ for the Reactor Network.
Reactor Network Soot Sections Diameters Mid-point diameter of each soot section for the Reactor Network.

For more information about using Soot PSDF reports, see Plotting Soot Sectional Particle Size Distribution.

Field Functions

Soot Mass Density: $m_{s o o t}$ in Eqn. (3750).
Soot Mass Fraction Sec[n]: ${\tilde{Y}}_{i, s o o t}$ for section $i$ , in Eqn. (3715).
Soot Mean Diameter: $d_{p}$ in Eqn. (3752).
Soot Nucleation Rate: ${(\frac{d N}{d t})}_{n u}$ in Eqn. (3658).
Soot Number Density: Total soot number density $N_{t o t}$ given by Eqn. (3753).
Soot PSDF Sec[n]: Soot particle size distribution function $\frac{d N}{d \log (d_{p})} (i)$ for section $i$ , given by Eqn. (3754).
Soot Total Mass Fraction: Sum of $Y_{i, s o o t}$ from $i$ to $i_{\max}$ .
Soot Volume Fraction: $f_{v}$ in Eqn. (3751).
Steric Factor: $α$ in Eqn. (3714).

Tables

Soot Sectional Particle Size Distribution Table - Boundaries / Regions: See Tables Reference.; For instructions on plotting the particle size distribution for soot sections, see Plotting Soot Sectional Particle Size Distribution.

Soot Sections > Soot

Allows you to specify specific material properties for the soot material.

Soot Sections > Soot Model Properties

Allows you to set properties to define the soot sections.

When using the Reactor Network model, the Reactor Network > Emissions > Soot Options node provides similar properties. See Soot Options.

Steric Factor Option

Allows you to specify the steric factor

α

in Eqn. (3706), that is, the fraction of reactive sites on the surface of the soot particle that are available for soot growth or oxidation reactions.

Method	Corresponding Sub Node
Constant	Steric Factor Allows you to define a constant value for Alpha (the steric factor $α$ ) between 0 and 1.
Premixed Temperature Correlation Uses fitted correlation from Appel et al. [781] for $α$ , where $α$ is a function of the local temperature and the average soot particle size, quantified by the reduced soot moment $μ_{1}$ , see Eqn. (3714).	None
User Defined Profile	User-Defined Steric Factor Allows you to define the steric factor using a scalar profile.

Nucleation Option

Only available as a property of the Soot Moments model or Soot Sections model when using the Complex Chemistry, Reactor Network, ECFM-3Z, or ECFM-CLEH combustion model. When using one of the Flamelet combustion models, you specify the nucleation option as a combustion table parameter.

Allows you to specify the Nucleation Option as either:


Nucleation Option	Corresponding Sub-Node
Single PAH Species (C16H10): See Eqn. (3679) and Eqn. (3680). The PAH precursor is recognised as any species which includes either A4 or A3R5 in the species name, or has the composition C16H10.	None
C2H2: See Eqn. (3682).	None
Multi PAH Species Allows you to select multiple PAH precursor species from those that are present in the chemical mechanism. Simcenter STAR-CCM+ recognises the chemical symbols of the PAH precursor species as described within the table for Multi PAH Species Nucleation. Available only when using the Complex Chemistry or Reactor Network combustion models.	PAH Species Components Lists the selected PAH precursor species—each displays its Sticky Coefficient property.

(Soot) Surface Chemistry Option


(Soot) Surface Chemistry Option	Corresponding Sub-Node
HACA The soot surface growth is modeled using the Hydrogen-Abstraction-C2H2-Addition (HACA) surface mechanism. Most appropriate when using the Complex Chemistry model. See HACA.	None
HACA RC The soot surface growth is modeled using the Hydrogen-Abstraction-Carbon-Addition-Ring-Closure (HACA-RC) surface mechanism. Most appropriate when using an ECFM model for diesel fuel. See HACA RC.	None

Surface-growth Scale

Scales surface growth

{\tilde{Ω}}_{i, s g}

in Eqn. (3717).

Nucleation Scale

Scales nucleation

{\tilde{Ω}}_{i, n u c}

in Eqn. (3717).

Oxidation Scale

Scales oxidation

{\tilde{Ω}}_{i, o x}

in Eqn. (3717).

Coagulation Scale

Scales coagulation

{\tilde{Ω}}_{i, c o a g}

in Eqn. (3717). Increasing this value increases the soot mean diameter.

Two-Way Coupled Species

In soot reactions, gas phase species are transferred to and from the gas phase to the soot particles. When this property is activated, these gas-phase species are added and removed from the gas-phase simulation. Only available when using a reacting species transport model or the Reactor Network model.

Soot Sections > Soot Model Properties > Sectional Properties

Number of Sections: Number of discrete sections in the particle size distribution function (PSDF).
Maximum Soot Diameter: Maximum diameter to which the soot particle grows.
Small Diameter Fractal Dimension: Surface growth fractal dimension of soot particles with a diameter $θ$ less than 20nm in Eqn. (3742) and Eqn. (3743). You can set this between 2.0 and 3.0.
Large Diameter Fractal Dimension: Surface growth fractal dimension of soot particles with a diameter $θ$ greater than 60nm in Eqn. (3742) and Eqn. (3743). You can set this between 2.0 and 3.0.

Soot Sections > Soot Model Properties > Steric Factor

Alpha: The steric factor $α$ for surface reactions in HACA or HACA-RC mechanisms.