Timed Nozzle Control #14267
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Hi All, I am trying to control a nozzle in FDS so that it turns on at a given time, then a little while later turns off again. I am trying to use the control method shown in example "activate_sprinklers.fds". I have set up my code so that the nozzle should ramp up between 99.9s & 100.0s, and ramp down between 199.9s & 200.0s. If I view the output file, only the 200s control shows, no mention of the 100s activation. Has anyone seen this behavior before? Is there a fix, or a better way to control the sprinkler. My code is as follows: &HEAD CHID= 'SPRINKLER_002' / &DUMP NFRAMES= 300, &TIME T_BEGIN= 000.00 / &TIME RESTRICT_TIME_STEP=F / &MISC TMPA= 10.99, &MESH IJK= 12, 12, 10, XB= 0.00, 3.00, 0.00, 3.00, 0.00, 2.50 / &VENT XB= 0.00, 0.00, 0.00, 3.00, 0.00, 2.50, SURF_ID= 'OPEN', COLOR= 'BLUE' / &OBST XB= 0.00, 3.00, 0.00, 3.00, 0.00, 0.25, COLOR= 'GREEN', TRANSPARENCY= 1.0 / &SPEC ID='SPRINKLER WATER VAPOR',SPEC_ID='WATER VAPOR' / &DEVC XYZ=0.25, 0.25, 0.25, ID='TIMER', QUANTITY='TIME' / &CTRL ID='CTR1', FUNCTION_TYPE='CUSTOM', INPUT_ID='TIMER', RAMP_ID='RAMP1', LATCH=.FALSE. / &PART ID='DROPS', &PROP ID='SPR_PROP', &DEVC ID='SPR1', &BNDF QUANTITY='MPUA', PART_ID='DROPS' / |
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Replies: 1 comment 4 replies
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Interestingly, if I remove "&TIME RESTRICT_TIME_STEP=F /" the control timings work, however, it takes much longer to simulate the last 100s (as you'd expect due to shorter time steps). |
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The .out file just reports the last state change time. Things like smoke detectors and sprinklers with a link would just have a single state change. The log.csv file should show all the state changes. Are you running with the current release? Since you know in advance the time you want the sprinkler flowing water, you could have a FLOW_RAMP for the PROP and for the sprinkler DEVC use TIME as the QUANTITY with a SETPOINT of 0 (can just change the -1 to 0 in your current RAMP). |
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Thank you drjfloyd! I'm running FDS 6.7.6 The FLOW_RAMP for the PROP works and is simpler. I will use that in future, thank you. It still has the issue due to "&TIME RESTRICT_TIME_STEP=F /", but I think that's due to my model having nothing happening for the first 100s, therefore the time steps are getting unrealistically long, resulting in the delayed start of the sprinkler, once the sprinkler is on, the time steps reduce and the command to turn off is much more accurate. Kind regards, Paul |
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6.7.6 is 6 soon to be 7 versions old. Unless you are being required to use a specific version by your local AHJ, would recommend updating your version. We have since 6.7.6 fixed various bugs associated with sprinklers and control logic. |
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I would not set RESTRICT_TIME_STEP=F. You can wind up with very large time steps and if you have things activating or deactivating you could get bad timing by having poor time resolution. With CFD you have errors related both to grid size and timestep size. Here is a plot of your timestep data from the steps.csv file. Your timestep is 10 s near when the sprinkler is activating. So 110 s is because that is the first time step that happens after your RAMP turns on the sprinkler.
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The .out file just reports the last state change time. Things like smoke detectors and sprinklers with a link would just have a single state change. The log.csv file should show all the state changes.
Are you running with the current release?
Since you know in advance the time you want the sprinkler flowing water, you could have a FLOW_RAMP for the PROP and for the sprinkler DEVC use TIME as the QUANTITY with a SETPOINT of 0 (can just change the -1 to 0 in your current RAMP).