You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
Copy file name to clipboardExpand all lines: Manuals/FDS_Verification_Guide/FDS_Verification_Guide.tex
+20-12Lines changed: 20 additions & 12 deletions
Original file line number
Diff line number
Diff line change
@@ -3999,29 +3999,37 @@ \section{Mixing with detailed chemistry (\ct{edc\_mixing\_cvode})}
3999
3999
4000
4000
This implementation has been validated against results obtained using Cantera~\cite{cantera:2023}. Note that Cantera does not provide a direct method to solve the coupled mixing-chemistry ODE system as done here in FDS; therefore, in Cantera an operator splitting approach was employed, where mixing and chemistry are handled sequentially. Specifically, within each CFD timestep (0.1 s), substeps for chemistry calculations in Cantera are kept sufficiently small (0.0001 s) to resolve the fast dynamics. All comparisons are carried out using the GRI-Mech 3.0 chemical mechanism~\cite{gri3:1999}.
4001
4001
4002
-
Figure~\ref{fig:edc_mixing_cvode_onecfdstep_vary_zeta0} presents comparisons of temperature and OH mass fraction between FDS and Cantera within a single CFD timestep for five constant-volume ignition delay cases, with varying initial unmixed fractions \(\zeta_0 = 1.0, 0.75, 0.5, 0.25, 0.0\).
4002
+
Figures~\ref{fig:edc_mixing_cvode_onecfdstep_vary_zeta0_1} and~\ref{fig:edc_mixing_cvode_onecfdstep_vary_zeta0_2} presents comparisons of temperature and OH mass fraction between FDS and Cantera within a single CFD timestep for five constant-volume ignition delay cases, with varying initial unmixed fractions \(\zeta_0 = 1.0, 0.75, 0.5, 0.25, 0.0\).
4003
4003
4004
4004
Figure~\ref{fig:edc_mixing_cvode_multicfdstep_vary_zeta0} shows similar comparisons over multiple CFD timesteps for the same ignition delay cases and initial unmixed fractions. These results also verify that elemental mass is conserved throughout the entire process.
4005
4005
4006
4006
Finally, Figure~\ref{fig:edc_mixing_cvode_onecfdstep_vary_taumix} compares temperature and OH mass fraction for a single CFD timestep across five cases with varying mixing times \(\tau_{\text{mix}} = 0.1, 0.01, 0.001, 0.0001, 0.00001\) s. As the mixing time decreases, the solution becomes independent of \(\tau_{\text{mix}}\), approaching the well-stirred reactor limit corresponding to (\(\zeta_0 = 0.0\)).
\caption[Results of the \ct{edc\_mixing\_cvode} test cases]{Comparison of CVODE substeps for a single CFD step of 0.1 s, showing the effect of varying the initial unmixed fraction between FDS and Cantera. The simulation uses the Methane GRI mechanism with an equivalence ratio of 0.6, a mixing time of 0.01 s, and an initial temperature of 1200 K.}
0 commit comments