Smoke Detector not activating for a revised model #15220
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Hi, I have building model where for the same scenario two different versions the smoke detection performs differently. For one version it activates as expected while for the other it does not. I have checked the .fds files and the code related to the activation control is identical. I am a beginner here and using Pyrosim for modelling. Code segment where activation works: Code segment where it does not work: Any help is greatly appreciated. Thank you. |
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Replies: 1 comment 3 replies
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These appear to be identical sets of inputs suggesting the issue is something else in your input files. Carefully review your outputs to make sure your model is doing what you expect in terms of smoke movement. In the case with isses do you have the fire you expect, are you seeing soot at the detector locations, etc. If after careful review you have not determined a cause, then attach a complete input file that demonstrates the issue you are having and clearly define exactly what is happening that you believe to be incorrect. (i.e. what does not activating as expected mean? too early, too late, not at all, something else?). |
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Thanks for a prompt response. To provide more input, the smoke movement is quite similar in the two cases (and as expected). The fire is also as expected and soot can be visualised near the detector locations for both cases. The difference in terms of output is that in one case smoke detectors pick up the soot and activate the desired vents and obstructions, while in the other case the smoke detector does not activate (not at all). The other difference is that the mesh resolution has become finer from 0.2m to 0.1m across all meshes. In your experience, if there are any plausible checks or causes to look into, I would be grateful to know them. As suggested, I will do another review of the .fds input file and get back with the outcome. Thanks! |
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Changing the grid resolution can change how OBST snap to the grid. Look at the smoke detector output in the DEVC file. Are you seeing zero soot or are you seeing soot but not enough to activate? If you are seeing zero soot, then look carefully at the geometry with smokeview and check if changing the grid has meant the ceiling snapping to a different grid location and put your detector inside a solid. If you are seeing soot, then compare with the case where it activated. Is it significantly different or just slightly different but still enough to not reach the detection threshold. |
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It is indeed the case where the OBST has snapped to the grid cell below the location of the detectors. I did not know about this behaviour, thank you for pointing it out and appreciate the promptness. |
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Changing the grid resolution can change how OBST snap to the grid. Look at the smoke detector output in the DEVC file. Are you seeing zero soot or are you seeing soot but not enough to activate? If you are seeing zero soot, then look carefully at the geometry with smokeview and check if changing the grid has meant the ceiling snapping to a different grid location and put your detector inside a solid. If you are seeing soot, then compare with the case where it activated. Is it significantly different or just slightly different but still enough to not reach the detection threshold.