{"id":362806,"date":"2024-04-17T21:34:27","date_gmt":"2024-04-17T21:34:27","guid":{"rendered":"\/forum\/forums\/reply\/362806\/"},"modified":"2024-04-17T21:34:27","modified_gmt":"2024-04-17T21:34:27","slug":"362806","status":"publish","type":"reply","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/reply\/362806\/","title":{"rendered":"Reply To: to find max velocty of a bullet released from a pressure of 10psi from a cylindr"},"content":{"rendered":"<p>&lt;p&gt;In snip 1, I see that the pressure starts at 90 psi but ramps down linearly to 0 at 1e-3 seconds, so the average pressure over that 1 ms is 45 psi, not 90 psi.&nbsp; You need to introduce a second step that ends when you want the pressure to end and keep the 90 psi at the start of that second step, then add a 3rd step that ends1e-5 seconds after the end of step 2 then in the Pressure Tabular data, you can type a 0 for the pressure in step 3.&lt;\/p&gt;&lt;p&gt;In the last snip, I see that you have turned Auto Time Stepping Off and the Time Step is 1e-3 s.&nbsp; That means the solver is not updating the pressure between t=0 s and t=0.001 s so maybe you are getting the full 90 psi for the first 1 ms.&nbsp; Perhaps this is why the results are changing when you use different Time Steps.&nbsp; The proper way to do simulation is to reduce the time steps until the answers stop changing.&lt;\/p&gt;&lt;p&gt;Once the simulation reaches step 3, the velocity should change from increasing to nearly constant, except for the drag force, which I don&#8217;t see in this simulation.&lt;\/p&gt;&lt;p&gt;In snip 2 I see that the velocity keeps increasing after the pressure has turned off. I don&#8217;t see any load that is continuing to accelerate the bullet after the pressure turns off at 1e-3 seconds so I would say this simulation is producing wrong results.&nbsp; It might start producing accurate results if you turn on Auto Time Stepping and use a much smaller Initial and Minimum Time step such as 1e-5 seconds.&lt;\/p&gt;<\/p>\n","protected":false},"template":"","class_list":["post-362806","reply","type-reply","status-publish","hentry"],"aioseo_notices":[],"acf":[],"_links":{"self":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/362806","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies"}],"about":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/types\/reply"}],"version-history":[{"count":0,"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/replies\/362806\/revisions"}],"wp:attachment":[{"href":"https:\/\/innovationspace.ansys.com\/forum\/wp-json\/wp\/v2\/media?parent=362806"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}