firemodels / fds

Fire Dynamics Simulator
https://pages.nist.gov/fds-smv/
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Wind velocity is not right at reference elevation #12300

Closed mcgratta closed 9 months ago

mcgratta commented 11 months ago

In this case, the specified wind speed is not achieved at the reference elevation

&HEAD CHID='Case_6_new' TITLE='Description of flt1fuel1mps' /

&TIME T_END=360. /

&MULT ID='Meshes' DX=200. I_UPPER=3 DY=200 J_UPPER=3 /
&MESH IJK=50,50,50 MULT_ID='Meshes' XB=-400.,-200.,-400.,-200.,0.00,200. /

&VENT MB='XMIN' SURF_ID='OPEN' /
&VENT MB='XMAX' SURF_ID='OPEN' /
&VENT MB='YMIN' SURF_ID='OPEN' /
&VENT MB='YMAX' SURF_ID='OPEN' /
&VENT MB='ZMAX' SURF_ID='OPEN' /

&DEVC ID='u', XB=10,10,10,10,1,199, POINTS=50 QUANTITY='U-VELOCITY' /
&DEVC ID='T', XB=10,10,10,10,1,199, POINTS=50 QUANTITY='TEMPERATURE' /

&SLCF PBY=0.00 QUANTITY='VELOCITY' /
&SLCF PBY=0.00 QUANTITY='TEMPERATURE' VECTOR=T /

&WIND SPEED=1., DIRECTION=270, L=-100., Z_0=0.03, Z_REF=20 /

&TAIL /
mcgratta commented 11 months ago

image

mcgratta commented 11 months ago

The reference temperature and velocity were not exactly achieved at the reference elevation. They should now be.

mcgratta commented 11 months ago

You can download a test version of FDS that fixes the issue of reference velocity, temperature and height. Check that things work and then we can address other issues if they still exist.

shahabck3 commented 11 months ago

Thanks, Kevin, I will give it a go!

mcgratta commented 11 months ago

Did this fix the problem?

shahabck3 commented 11 months ago

I did not have a chance to try it yet, I was running other tasks.

I will work on it this week and let you know.

Thanks

mcgratta commented 10 months ago

Thanks for checking.

shahabck3 commented 10 months ago

Dear Kevin, I have to say that I don't know how, but still I get incorrect results in some cases.

I ran two cases with a stable stratification, and the wind readings were lower than specified at the reference height.

mcgratta commented 10 months ago

Are you saying you don't know how to install a nightly build? The nightly builds are here.

shahabck3 commented 10 months ago

No, I'm saying that I ran some tests with the nightly build, but the windspeed was lower than specified at reference elevation.

mcgratta commented 10 months ago

Could you post a case that has a lower than specified wind speed.

shahabck3 commented 10 months ago

Sure, here is the case for 2m/s wind @ 6m reference height. But the readings at 6m is around 1.6m/s flt1fuel2mps_line.csv [flt1fuel2mps.txt](https://github.com/firemodels/fds/files/13952608/flt1fuel2mps.txt)

mcgratta commented 10 months ago

You need to establish the GROUND_LEVEL on the WIND line.

mcgratta commented 10 months ago

It is difficult to debug your case because the vertical grid resolution is 2 m. Look at this case

&HEAD CHID='wind' /
&TIME T_END=300. /
&MESH IJK=100,100,20, XB=-50.,50.,-50.,50.,1.,21. /
&VENT DB='XMIN' SURF_ID='OPEN' /
&VENT DB='XMAX' SURF_ID='OPEN' /
&VENT DB='YMIN' SURF_ID='OPEN' /
&VENT DB='YMAX' SURF_ID='OPEN' /
&VENT DB='ZMAX' SURF_ID='OPEN' /
&DEVC ID='u', XB=0,0,0,0,1.5,20.5, POINTS=20, QUANTITY='U-VELOCITY' /
&SLCF PBY=0.00 QUANTITY='TEMPERATURE' VECTOR=T /
&WIND SPEED=2., DIRECTION=270., L=1000000 , Z_0=0.03, Z_REF= 6, GROUND_LEVEL=1 /
&TAIL /
mcgratta commented 10 months ago

Anything further on this issue? Are you still having trouble?

shahabck3 commented 10 months ago

I am running a simulation with a smaller mesh size, but it's taking a bit of time. I will let you know as soon as it finishes.

mcgratta commented 9 months ago

I'm going to close the issue. Start a new issue if there are still problems, or reopen this one.