Predicting the mean and RMS fields in subsonic hydrogen jet fires

In this paper two modelling approaches for predicting the mean and root mean squared (RMS) fields of turbulent hydrogen jet fires are evaluated. This is of interest if the turbulence–radiation interaction in such jets is to be modelled rigorously. One of the modelling strategies is based on calculating the variance of the fields of interest from a prescribed probability density function (PDF) and the second is to solve a modelled transport equation for field variances. In addition three different PDFs are considered: a β PDF, a clipped Gaussian PDF and a truncated Gaussian PDF. The different modelling strategies are evaluated using a number of experimental jet fires taken from the open literature. The conclusions of the study are the PDF approach for predicting the RMS fields are superior to solving a transport equation for the variance of the field variables of interest. Of the PDFs considered the β PDF and truncated Gaussian PDF give similar predictions of the jet fire structure being more accurate than the clipped Gaussian PDF.

► The mean flow fields are predicted with good accuracy by all three PDFs considered.
► Calculating the variance from a PDF is more accurate than a transport equation.
► Of the PDFs considered the clipped Gaussian was the least accurate.
► A PDF satisfying only the 0th moment can predict the flame structure accurately.
► The flame structure model forms a good basis for studying TRI.