# Pressure difference at outlet

 Register Blogs Members List Search Today's Posts Mark Forums Read

 April 13, 2004, 20:44 Pressure difference at outlet #1 Nessan Guest   Posts: n/a Dear friends, In my simulation the reference pressure was set to zero and the outlet was also set to zero pressure. Then hydrostatic pressure was applied in the domain. After some iterations, I check the pressure at the outlet (in CFX-Post), it is less than the specified pressure. In addtion, both the total pressure and pressure (I guess it is the relative static prssure in CFX-Post). I am doing incompressible fluid simulation and 2nd differencial scheme was used. Thanks,

 April 14, 2004, 01:51 Re: Pressure difference at outlet #2 Nessan Guest   Posts: n/a Hello, everyone, I even checked the example result file - StaticMixer_001.res - which was located at Example folder under CFX 5.6 installtion folder. I found that the calculated pressure is totally different from that specified at Out boundary. In the example, reference pressure is zero and the relative static pressure at OUT boundary is set to zero. However, if you use calculator, you will find the average pressure is 579.786 Pa and average total pressure is 8438.77 Pa. How does the difference between calculated pressure nad specified pressure come from? (I would think the Pressure in CFX Post as static pressure). In my simulation case, the static pressure at top surface should be zero theoretically because hydrostatic pressure is applied and the top surface was set to zero static pressure (reference pressure is zero), however, I got negative static pressure at the top surface after convergence. Anybody has any idea about that! Thanks, Nessan

 April 14, 2004, 12:36 Re: Pressure difference at outlet #3 Robin Guest   Posts: n/a Hi Nessan, By default, the conservative control volume values are loaded into Post. If you calculate the pressure on the conservative values, the resulting pressures will not be the same as the boundary condition, as they represent the values slightly inside the domain. Rather, you should load the "Hybrid" values (through the variables editor or using the button on the calculator panel). The result may not be exactly your boundary condition, but should be within round-off. Similarly, when you are plotting values on the boundary, select the hybrid option to view the actual boundary values. Regards, Robin

 April 18, 2004, 00:20 Re: Pressure difference at outlet #4 Nessan Guest   Posts: n/a Hi, Robin, Thanks for your response. Actually I draw a contour of pressure on the pressure boundary in Post using Hybrid option. Does this have anything to do with mass-pressure coupling? Thanks, Nessan

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post a.lynchy FLUENT 3 February 13, 2012 05:03 Shreyansh FLUENT 0 November 5, 2010 15:57 Dave FLUENT 1 August 12, 2004 17:39 Dan Moskal Main CFD Forum 0 October 24, 2002 22:02 DS & HB Main CFD Forum 0 January 8, 2000 16:00

All times are GMT -4. The time now is 10:40.