Thank you for your interest.<\/p>\n
I am currently performing a simulation using compressible flow and the VOF model<\/strong>.<\/p>\n I am encountering a situation where the absolute pressure becomes negative near the outlet of a narrow flow passage<\/strong>, particularly where the fluid exits into an air-filled region. The geometry can be considered similar to a nozzle, and the negative pressure appears near the nozzle exit boundary, approximately in the red-circled region in the figure<\/strong>.<\/p>\n The operating pressure is set to atmospheric pressure<\/strong>, and I have also confirmed that the pressure being examined in post-processing is absolute pressure<\/strong>, not static\/gauge pressure.<\/p>\n Due to the nozzle geometry, I understand that an air vortex is formed in the indicated region and that the local pressure can decrease<\/strong>. However, I am having difficulty understanding why the absolute pressure becomes negative<\/strong>.<\/p>\n I tested the following two cases:<\/p>\n In both cases, negative absolute pressure appeared at approximately the same location.<\/p>\n In the first case, where the air density depends on pressure, I also observed that the convergence deteriorates or the solution diverges as the nozzle velocity increases<\/strong>.<\/p>\n Therefore, my questions are:<\/p>\n For reference, I am using:<\/p>\n From a numerical stability perspective, I considered these settings to be fairly conservative.<\/p>\n In addition, since I wanted to model compressible flow without solving the energy equation<\/strong>, I selected the following approach\/settings. However, I did not expect it to result in negative absolute pressure.<\/p>\n I would appreciate any explanation regarding the physical or numerical reason for this behavior.<\/p>\n","protected":false},"template":"","class_list":["post-462612","topic","type-topic","status-publish","hentry","topic-tag-compressible-flow-air-2","topic-tag-vof"],"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
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