{"id":369991,"date":"2024-06-05T20:45:57","date_gmt":"2024-06-05T20:45:57","guid":{"rendered":"\/forum\/forums\/topic\/vacuum-chamber-air-extraction-from-1-atm-to-vacuum-in-a-closed-geometry\/"},"modified":"2024-06-05T20:45:57","modified_gmt":"2024-06-05T20:45:57","slug":"vacuum-chamber-air-extraction-from-1-atm-to-vacuum-in-a-closed-geometry","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/vacuum-chamber-air-extraction-from-1-atm-to-vacuum-in-a-closed-geometry\/","title":{"rendered":"Vacuum chamber – air extraction, from 1 atm to vacuum in a closed geometry"},"content":{"rendered":"

Hello there,<\/p>\n

I’m having a troubles with my simulation. I want to simulate the behaviour pressure over time of a parallelepiped vessel attached to a vacuum pump (which is just described by a mass flow outlet on the vessel). At the beginning of the experiment, there’s 1 atm of air inside the volume.<\/p>\n

The decrease in pressure I get is way less than what’s observed with the experiments and the analytical estimation. 
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My simulation is a watertight geometry with only one outlet.<\/p>\n

I use the Density based solver. The fluid is air from the material fluid list, and I changed “Density” parameter from constant to ideal gas, so density can vary, accordingly to P and T. (I tried other real gasses models as well, and tried many viscous models)<\/p>\n

My mesh has a good quality, I kept the number of nodes around 1M beceause it’s taking too long otherwise. (even as I’m computing on a Calculator)<\/p>\n

Transient simulation, time steps of 1e-4 s. The Solution is converging properly, with 20 it\/time step at the beginning and then reducing it to 3. <\/p>\n

From experimental and analytical pov, we know that we should observe a drop in pressure of about 5800 Pa in the volume after 10 seconds. However, The simulation only gives me a 10 Pa pressure drop. I’m attaching images here : https:\/\/www.swisstransfer.com\/d\/d29e23d6-0a70-48e6-923d-76c0e16e8a54 as i can’t attach them down here, idk why. <\/p>\n

What am I missing ? 
Thanks for your time reading me \"\"<\/p>\n","protected":false},"template":"","class_list":["post-369991","topic","type-topic","status-closed","hentry","topic-tag-pressure-drop","topic-tag-vacuum-chamber-1"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t