## 7.12. Turbulent Burning Velocity

For turbulent flow, the effective or turbulent burning velocity will differ from the laminar burning velocity, . Typically turbulence will increase the burning velocity, because wrinkling of the flame front results in an increased effective flame surface. At very high turbulence, the opposite effect may occur, leading to a decrease in the effective burning velocity because of local extinction. A model is required to describe the turbulent burning velocity as a function of laminar burning velocity and turbulence quantities.

The burning velocity is defined relative to the unburnt fluid. Relative to the burnt fluid, it will be higher by a factor equal to the fluid expansion ratio, .

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