## 7.10. Burning Velocity Model (BVM)

The burning velocity model (BVM), also known as turbulent flame closure (TFC), is used to close the combustion source term for reaction progress.

| (7–47)

| (7–48)

Where is the density of the unburnt mixture. Note that the molecular diffusion term for the reaction progress is removed from the transport equation. The diffusive exchange of species and energy, which makes the flame proceed in space, is already accounted for by the source term . However, turbulent transport is a convective process and is modeled using the Eddy Diffusivity approximation.

The model is completed with a closure for the turbulent burning velocity . Accordingly, this type of model is called Turbulent Burning Velocity Model (BVM). The concept has two significant advantages compared to models based on molecular reaction rates:

1. In a given configuration, typically varies by only 1 order of magnitude. In contrast, molecular reaction rates occurring in combustion of hydro-carbonates typically vary in the computational domain by several orders of magnitude.

2. can be measured directly in experiments, i.e., data is available for the quantity that is modeled.

Further, the burning velocity directly determines target quantities of a simulation, such as flame position. Thus, it is easier to derive and fine-tune accurate models for the burning velocity model than to do so for approaches based on molecular reaction rates.

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