The eddy dissipation model is based on the concept that chemical reaction is fast relative to the transport processes in the flow. When reactants mix at the molecular level, they instantaneously form products. The model assumes that the reaction rate may be related directly to the time required to mix reactants at the molecular level. In turbulent flows, this mixing time is dominated by the eddy properties and, therefore, the rate is proportional to a mixing time defined by the turbulent kinetic energy, , and dissipation, .

(7–6)

This concept of reaction control is applicable in many industrial combustion problems where reaction rates are fast compared to reactant mixing rates.

In the Eddy Dissipation model, the rate of progress of elementary reaction k, is determined by the smallest of the two following expressions: