UFR 1-07 Evaluation

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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.

Figure 11  An instantaneous snapshot of the DesJardin et al.‘s LES predictions showing an iso-contour of

vorticity magnitude at 5% of the maximum coloured according to the

magnitude of the gravitational torque.

Front Page

Description

Test Case Studies

Evaluation

Best Practice Advice

References

Contributed by: Simon Gant — UK Health & Safety Laboratory

© copyright ERCOFTAC 2010