# Modelling a fan

 User Name Remember Me Password
 Register Blogs Members List Search Today's Posts Mark Forums Read

 October 9, 2006, 10:08 Modelling a fan #1 Richard Guest   Posts: n/a Hallo, I am modelling a fan using a sub domain whith a defined momentum source, momentum source coefficient and redistribute options on. Only my results do not match measurements. The speed in the fan is allmost the same as in reality. The problem is: The air movement is not diverging like in reality. The airspeed is at about 35 meter after the fan still in a range of 6 meters. The measurements show results where at 35 meters the air is moving in a range of 15 meters. So the moving air does not have a lot of influence on the other air. I don't know what i'm doing wrong. I'm using the K epsilon model. Thanks in advance, Richard

 October 9, 2006, 17:09 Re: Modelling a fan #2 Glenn Horrocks Guest   Posts: n/a Hi, Do you mean the jet coming out of the fan is not dissipating as measurements show? To get the dissipation right you will need to have the correct turbulence levels in the jet created by the fan (amungst many other things you will need to get right for an accurate simulation). If you model the fan by a momentum source you will need to put in an appropriate turbulence source as well. Glenn Horrocks

 October 10, 2006, 02:08 Re: Modelling a fan #3 Richard Guest   Posts: n/a Thanks Glenn, I ment the jet coming out of the fan indeed. I also didn't put in a tubulence source so that probalbly causes the unrealistic results. I only have no idea what value the Turbulence eddy dissipation or turbulence kinetic energy should be. I also can't find a formula in the maual. Is there a standard formula to calculate these values? Do i also need to set the option for viscous dissipation in the domain on? Thanks a lot for the help, Richard

 October 10, 2006, 09:48 Re: Modelling a fan #4 Bian Guest   Posts: n/a I have no experience on jet flow, however, I do simulate the fans (from inlet to outlet). I would say the tubulence source will be a guess or estimate according to flow speed and outlet size. If I work on your problem, I will take the outlet boundary of my fan simulation as the inlet boudary of the jet flow. Bian

 Thread Tools Search this Thread Search this Thread: Advanced Search 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 Off Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post buzzybee CFX 10 June 11, 2009 20:15 Jenny CFX 3 September 30, 2007 08:47 Jenny CFX 8 September 11, 2007 13:59 Moke Main CFD Forum 1 March 28, 2005 20:28 suitto FLUENT 1 March 21, 2000 11:46

All times are GMT -4. The time now is 23:23.

 Contact Us - CFD Online - Privacy Statement - Top