Reacting Flow
Simcenter STAR-CCM+ provides a selection of models that you can use to simulate a wide range of reacting flow applications.
In Simcenter STAR-CCM+, there are two specific categories of reacting flow models, Flamelet, and Reacting Species Transport. Whenever applicable, you use the flamelet models, otherwise, you use the reacting species transport models. To decide on a modeling approach, it is important to consider the relation between the rate at which species react and the rate at which species mix (the chemistry time-scales and turbulence time-scales).
You can create simple chemical mechanisms in Simcenter STAR-CCM+ either manually or using the flamelet table generators, or you can import more complex chemical mechanisms from another source, such as DARS. A selection of ignitors are also available to use with most combustion models in Simcenter STAR-CCM+.
Simcenter STAR-CCM+ provides the option to use the Adaptive Mesh model in conjunction with a combustion model. This combination improves the ability of the volume mesh to resolve the internal flame structure by adapting the cell sizes within the existing mesh according to a scalar range that is specified for a selected variable, such as species mass fraction, temperature, and/or progress variable.
Flamelet
In Simcenter STAR-CCM+, the chemistry is calculated using detailed chemical mechanisms in simple 0D or 1D laminar flamelet geometries. The results are then tabulated and interpolated in a 3D simulation of a turbulent flame.
| Flamelet Models | Description | Applications |
|---|---|---|
| Flamelet Generated Manifold | Mainly for premixed or partially-premixed flames where the flamelet assumption is valid. |
|
| Steady Laminar Flamelet | Mainly for non-premixed combustion where the flamelet assumption is valid. |
|
| Chemical Equilibrium | When only the temperature is of interest, or there is no chemical mechanism available. |
|
- Turbulent Flame Closure
- Coherent Flame Model
See, Flamelet.
Reacting Species Transport
Simcenter STAR-CCM+ solves transport equations for all species and applies a separate mechanism for predicting the chemistry. Possible mechanisms range from simple one or two step reactions to those that require complex chemistry.
| Reacting Species Transport Models | Description | Applications |
|---|---|---|
| Complex Chemistry | For capturing transient phenomena and slowly forming species in gaseous combustion. |
|
| Eddy Break-Up | For quick flame positioning in gaseous combustion. |
|
| Thickened Flame Model | For premixed or partially premixed flames in Large Eddy Simulations (LES), when flamelet models cannot be used. |
|
| Eddy Contact Micromixing | For liquid-liquid chemistry, where the chemistry is fast compared to mixing. | Liquid-Liquid Reactors |
| Polymerization | For polymerization reactions. | Polymerization Reactors |
Other Reacting Flow Models
- Emissions:
Simcenter STAR-CCM+ provides specific emissions models that you can use with the specific reacting flow models to simulate slowly forming pollutant species, such as Soot, NOx Thermal, NOx Prompt, and NOx Fuel.
See, Emissions.
- Surface Chemistry: Surface chemistry describes the interaction between fluid molecules and a solid surface material. You can model surface chemistry independently or as an additional option alongside other categories of reaction models.
See, Surface Chemistry.
- Reacting Channels: The Reacting Channels model is designed to simulate chemical processes that occur within long narrow tubes.
See, Reacting Channels.
- Interphase: By using combustion models in combination with relevant multiphase models, you can simulate reacting solid particles or fluid droplets.
See, Modeling Multiphase Flow.
- Reactor Network: Once the flame position for a steady-state simulation is calculated using a simple and fast combustion model (a flamelet model or EBU), the Reactor Network model calculates the detailed chemistry within a network of reactors that contain clusters of contiguous cells with similar compositions. Avoids the computational cost of solving detailed chemistry for each cell in the computational domain.
See: Reactor Network.
| Optional Reaction Models | Description | Applications |
|---|---|---|
| Emissions | For NOx and soot prediction. |
|
| Particle Reactions (see Interphase) | For combustion of solid particles |
|
| Surface Chemistry | For catalyses and surface deposition or etching. |
|
| Reacting Channel | For fast calculation (1D) of chemical reactions in long channels. |
|
| Interphase Reactions | For phase-changing reactions. |
|
| Reactor Network | To rapidly simulate detailed chemistry in steady combustors. |
|