{"id":250330,"date":"2023-02-17T07:10:38","date_gmt":"2023-02-17T07:10:38","guid":{"rendered":"\/forum\/forums\/topic\/density-of-fluid-affects-the-results-and-it-makes-the-result-wrong\/"},"modified":"2023-02-17T07:21:44","modified_gmt":"2023-02-17T07:21:44","slug":"density-of-fluid-affects-the-results-and-it-makes-the-result-wrong","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/density-of-fluid-affects-the-results-and-it-makes-the-result-wrong\/","title":{"rendered":"Density of fluid affects the results and it makes the result wrong."},"content":{"rendered":"

Hello everyone. 
I am working with 2D simulation with dynamic mesh. My geometry looks like that:
<\/a>
I have 1 inlet (210 bar) and 2 outlets (0 bar). There is a motion and is defined via UDF. When the simulation starts, motion starts as well. Normally, I must use hydraulic oil properties which has 860 kg\/m3 density. When I use hydrualic oil density value, the results coming out are wrong. When I switch to air, which has 1.225 kg\/m3 density, the results coming are seem to be true. 
<\/a> <\/a>
The upper one is the result of air. Velocity values are wrong; however, the motion of the fluid from inlet to outlet ports are correct. 
The lower one is the result of oil. Velocity values may be wrong or true; however, the motion from inlet to outlet ports are definetly wrong. Here is the 1 time step after the beginning when I use oil:
<\/a> It begins like that and afterwards the results are coming wrong. <\/p>\n

For the both cases, the residuals are not diverging. However, for oil, the residuals are unstable compared to air residuals. Here is the graphs of residuals:


Upper one is for air; lower one is for oil.<\/p>\n

As a result, using high density value creates something with the simulation and makes the results wrong. I am using pressure-based solver with second order interpolators. Additionally, I have tried different approaches. I changed method, solver, spatial discretization types for all properties but still have the same issue. <\/p>\n

What do you think about this problem? And, how can I solve it and make the result true for hydraulic oil density value? 
(I have also animations of pressure and velocity for both simulations with air and oil. If you want to see it I can send a link of the animations as well.)<\/p>\n

Thanks.<\/p>\n

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