pressure output

[Jack82]

Dear all,

 

I would like to understand the pressure output provided with DEVC and hrr.csv and their use in validation work.

 

According to user guide, the background pressure of a pressure zone is given in hrr.csv. If I well understood, this pressure is the hydrostatics pressure calculated at the bottom of the zone. It only depends from altimetry and temperature. If the zone temperature is increasing, zone pressure will do the same.

Devices provide the perturbation pressure due to gas movement. 

 

The total pressure is then the sum of zone and perturbation pressures.

In validation guide, devices are used for the comparison to experimental data and I would like to understand why the sum Device + Pressure zone is not compared to pressure measurement which measure the total pressure?

Best regards

[dr_jfloyd]

The pressure in the HRR file is the background pressure at the bottom of the domain.  With the total pressure device it is the perturbation pressure plus the background pressure at the elevation of the device.

[C20]

Hello,

Old thread but I have a follow up question on your reply dr_jfloyd, The "total pressure device" equals Quantity = PRESSURE right? Hence the quantity PRESSURE gives you the perturbation pressure plus the background pressure at the elevation of the device? If so, what elevation is used for calulating pressure when measuring the output PRESSURE with STATISTICS over a volume?

[dr_jfloyd]

PRESSURE is the perturbation pressure (zone pressure at that elevation + hydrodynamic pressure - initial pressure at that elevation). ABSOLUTE PRESSURE is the total pressure.

If you are using a SPATIAL_STATISTIC, FDS calls the point device routine for each grid cell inside of XB, i.e., it is like you have a whole bunch of DEVC with XYZ at each grid cell in XB that you then do the SPATIAL_STATISTIC on.