Some aspects of scalar dissipation

Scalar dissipation is of great importance in the theory and modelling of combustion and other reacting turbulent flows. Measurements of scalar dissipation are found to lack the quality assurance of checks available from the conservation equations. Conditional averages of the scalar dissipation, so important in turbulent reacting flow theory and modelling, have qualitative and quantitative dependences that are very dependent on the details of the flow and mixing conditions. Accordingly, effort needs to focus on viable means of modelling it. Fluctuations of the scalar dissipation about the conditional mean are also important. Research results in this area need to be made more accessible to the combustion scientist. Heat release effects, so important in turbulent premixed combustion, are found to be much less important in non-premixed combustion.