Summary

This work applies especially to the modelling of turbulent diffusion flames when solving transport equations for a conserved scalar and its variance, and when adopting the Beta PDF as the assumed PDF, which is common practice. The solutions to the transport equations are limited to physically or mathematically valid ranges. However, setting limits to the temporary results during the iterative solution of the numerical model may lead to numerical difficulties, and it would be desirable to avoid them. This paper shows that in the present case there is no need for an upper limit to the variance equation.