Complex Chemistry Model Reference


Theory	See Complex Chemistry
Provided By	[physics continuum] > Models > [Combustion Models]
Example Node Path	Continua > Physics 1 > Models > Complex Chemistry
Requires	Material: Multi-Component Gas or Multi-Component Liquid Reaction Regime: Reacting Reactive Flow: Reacting Species Transport
Properties	Key properties are: Source Enabled Trigger, Begin. See Complex Chemistry Properties.
Specific Right-Click Actions	See Right-Click Actions.
Activates	Physics Models	Turbulence Chemistry Interactions See Turbulence-Chemistry Interactions Model Reference.
	Model Controls (child nodes)	Approximation Options, Chemistry Acceleration , CVODE, Acceleration Factor Control.
	Region Settings	Active Reactions
	Report Options	Chemistry Acceleration Factor, Complex Chemistry Quantity Parallel Max, Complex Chemistry Quantity Parallel Min, Complex Chemistry Quantity Parallel Sum. See Reports.
	Other Continuum Nodes	The Ignitors node provides the right-click option to create a Fixed Temperature Ignitor, ISSIM Spark Plug, or a Subgrid Spark Ignitor. See Ignitors.
	Field Functions	Chemistry Heat Release Rate, Chemistry Time Step, Clustering Equivalence Ratio, Clustering Index, Clustering Mixture Fraction, Number of DMR Retained Species. See Field Functions.

Complex Chemistry Model Properties

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.
Minimum Temperature For Reactions: Below this temperature, chemical reactions are deactivated.
Reaction Rate Multiplier: Tuning parameter that multiplies every reaction rate $r_{k}$ in Eqn. (3358) by this value. You can use this parameter to adjust the rate of chemical reactions which determine kinetic phenomena such as ignition delay times and premixed flame speeds.
Dynamic Load Balancing: When activated, dynamic load-balancing is turned on for complex chemistry calculations.

Right-Click Actions

Import Chemistry Definition (Chemkin format)

Activates an Import Chemkin Files dialog that allows you to import a chemical mechanism file, thermodynamic properties file, and optionally a transport properties file.

If you are using the Surface Chemistry model, the Import Chemkin Files dialog also allows you to import surface chemical mechanism files and surface thermodynamic properties files—you can select more than one of each.

Upon importing a chemistry definition, the reactions for the definition appear as sub-nodes of the Chemistry Definition node.

Delete Chemistry Definition

Removes the reactions, and optionally the species, that are used for the chemistry definition. Upon deletion, in the Output window, Simcenter STAR-CCM+ notifies from which regions, boundaries, or interfaces, the reactions are removed.

Delete Species?
Activated	All species and related properties from the mechanism are deleted.
Deactivated	All species and their related properties are maintained and are not overwritten when importing another Chemkin mechanism (any additional species are added—none are removed).

Region Settings

Applies to all regions:

Active Reactions Option: Activates or deactivates chemical reactions in this region.

Complex Chemistry Reports

Chemistry Acceleration Factor: When the Acceleration Factor Control property, Automatic Control, is activated, the chemistry acceleration plot shows the varying level of acceleration—between 0.0 (full $ω_{i}$ source term linearization—which is slow to run) and 1.0 (no $ω_{i}$ source term linearization—which is faster to run, but less stable).

The following Complex Chemistry reports take a particular value and perform a global operation (maximum, minimum or sum) over all of the processors. For a serial run, all three types of reports report the same value. Several of the Complex Chemistry Variable options only produce reports with values when ISAT is used. If ISAT is not available, these reports have a zero value.

Complex Chemistry Quantity Parallel Max
Complex Chemistry Quantity Parallel Min
Complex Chemistry Quantity Parallel Sum

Complex Chemistry Reports Properties

The maximum, minimum or sum reports have the following properties available:

Units: The units that are used for specifying the quantity.

Complex Chemistry Variable

Allows you to choose the type of Complex Chemistry Variable to plot.

None
CPU Time: The time that the CPU takes for complex chemistry calculations with the ODE solver.
Elapsed Time: The time that has elapsed during complex chemistry calculations with the ODE solver.
Adds: The number of points that have been added to the table. (ISAT only).
Grows: The number of points in the table that have increased their region of accuracy. (ISAT only).
Retrieves: The number of points that are retrieved from the ISAT table; these retrieves avoid expensive direct ODE solver calculations (ISAT only).
Direct Evaluations: The number of points that are calculated by calling the ODE solver. (ISAT only).
Table Size: The ISAT table size.
Queries: The total number of queries given to ISAT.
Direct ODE Queries: The number of queries that result in direct ODE solver calculations. Low values in this report reflect a good setup of ISAT parameters.

Variable Accumulation Type

Format of displayed value for those Complex Chemistry Variables that report a value of time.

Cumulative:
The time taken for the complex chemistry solver calculations in all iterations.
Per Iteration : The time taken for the complex chemistry solver calculation for each iteration.

Field Functions

Chemistry Heat Release Rate: The chemistry heat release shows the amount of heat that is released due to complex chemistry reactions. This value is $\dot{h}$ in Eqn. (3366).
Chemistry Time Step: For steady state simulations, the chemistry time step is the total time that is spent integrating the chemistry in the cell.
Clustering Equivalence Ratio: The clustering equivalence ratio is defined by Eqn. (3432).
Clustering Index: Clustering index is an integer value showing the cluster that the cell belongs to. Values of zero represent cells which are not chemically active, such as cells with a temperature below the Minimum Temperature for Reactions.
Clustering Mixture Fraction: The clustering mixture fraction is defined as the atomic mass fraction that originates from the fuel stream. Since the fuel is assumed to be hydrocarbons, the clustering mixture fraction is the mass fraction of C and H in the cell.
Number of DMR Retained Species: Available when the chemistry acceleration property, Dynamic Mechanism Reduction, is activated. Displays the actual number of species from the full chemical mechanism that the CVODE solver retains and solves for.