UFR 1-07 Evaluation: Difference between revisions

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Figure 11 shows a snapshot of the flow field predicted by the CFD model
Figure 11 shows a snapshot of the flow field predicted by the CFD model
of DesJardin \textit{et al}. [1]. With the coarse grid, the plume
of DesJardin ''et al.'' [[UFR_1-07_References#1|[1]]]. With the coarse grid, the plume
puffing frequency was found to be approximately 1.8 Hz, much higher
puffing frequency was found to be approximately 1.8 Hz, much higher
than the frequency measured in the experiments of 1.37Hz. The
than the frequency measured in the experiments of 1.37 Hz. The
predictions improved as the grid was refined, with the fine grid
predictions improved as the grid was refined, with the fine grid
producing a frequency of 1.5 Hz. A similar frequency was obtained with
producing a frequency of 1.5 Hz. A similar frequency was obtained with
or without an SGS model. DesJardin \textit{et al}. [1] also presented
or without an SGS model. DesJardin ''et al.'' [[UFR_1-07_References#1|[1]]] also presented
results from a simulation with no SGS model and a very coarse mesh
results from a simulation with no SGS model and a very coarse mesh
(220k nodes in total and only 30 cells across the source diameter).
(220k nodes in total and only 30 cells across the source diameter).
This produced a puffing frequency of 1.7 Hz, which they considered to
This produced a puffing frequency of 1.7 Hz, which they considered to
be an adequate estimate for engineering purposes, although the axial
be an adequate estimate for engineering purposes, although the axial
velocity in this case was overpredicted by nearly a factor of two.  
velocity in this case was overpredicted by nearly a factor of two.  


{{UFRHeader
{{UFRHeader

Revision as of 18:54, 12 July 2010


Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References

Unsteady Near-Field Plumes

Underlying Flow Regime 1-07


Comparison of DesJardin et al. [1] CFD Calculations with Experiments

Figure 11 shows a snapshot of the flow field predicted by the CFD model of DesJardin et al. [1]. With the coarse grid, the plume puffing frequency was found to be approximately 1.8 Hz, much higher than the frequency measured in the experiments of 1.37 Hz. The predictions improved as the grid was refined, with the fine grid producing a frequency of 1.5 Hz. A similar frequency was obtained with or without an SGS model. DesJardin et al. [1] also presented results from a simulation with no SGS model and a very coarse mesh (220k nodes in total and only 30 cells across the source diameter). This produced a puffing frequency of 1.7 Hz, which they considered to be an adequate estimate for engineering purposes, although the axial velocity in this case was overpredicted by nearly a factor of two.


Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References


Contributed by: Simon Gant — UK Health & Safety Laboratory

© copyright ERCOFTAC 2010