Turbulence modelling of flows with non-uniform density

Large differences in flux density may be expected to alter the processes determining turbulent transport. The correct simulation of these alternations is important in many practical flows, notably in turbulent combustion. This thesis examines the problem of modelling non-uniform density turbulence and develops an appropriate second-moment closure. Careful consideration is given to the role of each exact term in the averaged conservation equations and in the equations for the second moment correlations. Where high order terms depending on density gradients or density fluctuations might make a significant contribution, appropriate representations are developed. Several new models are introduced which reflect the effect of density non-uniformity on the pressure scrambling process and on the way fluctuation energy is transferred from large-scale motions where turbulence is produced to the finest scales where it is destroyed.