# 6-dof rigid body solver

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

 July 11, 2011, 02:33 6-dof rigid body solver #1 New Member   AUN Join Date: May 2011 Posts: 11 Rep Power: 6 Dear All, I am working on a HAWT Project. The geometry of the blade is available, however, the power curves have to be generated given different input wind speeds and directions. For this purpose, I am applying the 6-DOF Rigid Body Solver in CFX. At first I modelled the fluid domain as a cuboid with the blades subtracted from it. Not only did the 6-DOF take insanely long (Mesh 2.2 million) however, after a rotation of three degrees, the solver crashed due to volume negativity. I had kept mesh skewness low, and the mesh was fine in proximity of the blade. The raeson why this problem is occuring is unclear to me. To counter this effect, I 'tried' doing the same as they have done in the Tutorial 'Decoupling Mesh Motion'. I created a subdomain in the fluid domain, a cylinder, ascribed to it the same motion as the Rigid Body and ignoring rotations at the outer domain inrerfaces. The mesh at the boundary of the subdomain was conformal. Mesh Size 1.9 million made in ICEM CFD. The same negative element volume problem persisted. What can be done regarding this? Regards, Aun

 July 11, 2011, 06:47 #2 Super Moderator   Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 10,832 Rep Power: 85 I do not think you are using the correct approach. Forget 6DOF and FSI. The way to do this is to put the blades in a rotating frame of reference and assume a rotation speed. Do a simulation and get the net torque. If the net torque is positive (ie blades would accelerate) then do another simulation a bit faster. Keep iterating until you get the rotation speed which produces a torque which matches the load on the turbine. Once you have a few points on your speed versus torque curve you can use non-linear curve fits to greatly accelerate finding the converged value. This way you replace an extemely long and difficult to converge transient run with a series of simple steady state runs. Much simpler.

 July 11, 2011, 22:59 #3 New Member   AUN Join Date: May 2011 Posts: 11 Rep Power: 6 Dear Glenn, Thanks for your response. Best Wishes Aun

 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 wlt_1985 FLUENT 10 April 11, 2012 15:25 Luiz CFX 4 March 6, 2011 21:02 suitup OpenFOAM Running, Solving & CFD 0 January 20, 2010 08:45 Star-CCM+ User CD-adapco 1 February 11, 2009 15:14 wan CFX 1 February 28, 2008 17:41

All times are GMT -4. The time now is 09:49.

 Contact Us - CFD Online - Top