Revision as of 14:27, 9 July 2010

Unsteady Near-Field Plumes

Underlying Flow Regime 1-07

Test Case Study

Brief Description of the Study Test Case

\item A summary of the boundary conditions is shown in Figure 8. \item A gas mixture mainly composed of helium is discharged through a circular orifice into ambient air. \item The gas is composed of 96.4\% helium, 1.7\% acetone and 1.9\% oxygen by volume. \item The molecular weight of the gas released is 5.45 g/mol {\textpm} 2.7\%. \item The mixture is discharged at a temperature of \textit{T}\textit{\textsubscript{He}} = 11{\textdegree}C {\textpm} 3{\textdegree}C and the air is at \textit{T}\textit{\textsubscript{air}} = 13 {\textdegree}C {\textpm} 3{\textdegree}C. \ \ \item The circular plume source has diameter, \textit{D} = 1 metre. \item The helium is discharged at a Reynolds{}-averaged velocity \textit{V}\textsubscript{0} = 0.325 m/s {\textpm} 1.3\% and a Favre{}-averaged velocity of approximately 0.339 m/s. \item The flow through the orifice is \ laminar. \item The ambient pressure is 80.9 kPa {\textpm} 0.4 kPa. \item The measurements include: \end{enumerate} \liststyleLv \begin{enumerate} \item Time{}-history of vertical velocity at a point 0.5 m from the centreline and 0.5 m above the inlet, used to estimate the puffing frequency \item Measurements on a vertical plane through the plume from the plume source to a distance of one orifice diameter of:.

\begin{enumerate} \item Reynolds{}-averaged and Favre{}-averaged mean axial and radial velocities \item Reynolds{}-averaged and Favre{}-averaged shear stresses, normal stresses and turbulent kinetic energy\footnote{Only velocities parallel to a two{}-dimensional plane were recorded. The turbulent kinetic energy, \textit{k}, is calculated from the vertical and horizontal normal stresses ( $\overline{{\mathit{uu}}}$ and $\overline{{\mathit{ww}}}$ ) by assuming that the horizontal component is the same in the out{}-of{}-plane direction ( $\overline{{\mathit{vv}}}=\overline{{\mathit{ww}}}$ ), i.e. assuming that $k\approx \left(\overline{{\mathit{uu}}}+2\overline{{\mathit{ww}}}\right)/2$ .} \item Favre{}-averaged helium concentrations \end{enumerate} \item Movies of helium concentration and velocities \item Profiles of the mean and RMS velocities, and mean and RMS helium concentrations at six measurement positions (0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 m downstream of the plume source) \end{enumerate} Item 1 is available in the O{\textquotesingle}Hern \textit{et al}. [4] paper, Items 2 and 3 can be obtained by contacting the authors of the study\footnote{\textmd{Dr. Tieszen}\textmd{ (srtiesz@sandia.gov) or Dr. O{\textquotesingle}Hern (tjohern@sa}\textmd{ndia.gov).}} and Item 4 is presented by \textmd{\textup{Chung \& Devaud }}\textmd{\textup{[39]}}.