# Help with large sim

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

 May 30, 2007, 06:21 Re: Help with large sim #2 Phil Guest   Posts: n/a Theoretically, you could calculate the location of the free surface analytically and then use an icemcfd macro to generate a different mesh for each timestep. This would eliminate the air phase but this would only reduce the solving time modestly. Try using symmetry. A 2D approximation would reduce computing time by an order of magnitude. If you simply have to solve the 3D problem hire computing time on a cluster. Physical scale modeling is another option.

 May 30, 2007, 06:36 Re: Help with large sim #3 stu Guest   Posts: n/a I can't take advantage of symmetry but I have had a thought. Part 2 of tutorial 20 uses junction box routines to 'change the mesh' maybe this approach is possible. I have had another idea, could I use multiple domains that each represent say 10% of the height of the tank? Is there a way to turn off all calculation in a domian until I am ready to process that domain? I could process the bottom doam, wait until it gets to sday 50% full, then allow the domain that is sitting above it, that would be the 10 to 20% Height domain, to start calcualting. Any thoughts? Stu

 May 30, 2007, 07:04 Re: Help with large sim #4 Rui Guest   Posts: n/a Hi, Even if you managed to restrict your calculation domain to the liquid phase, your computation time would only be reduced to half: from 1.86 years to 0.93 years I think you'll have to stay quite below the 1M elements mesh. And try to use hexa elementes wherever possible Take a look at this: http://www.ansys.com/industries/cons...oiletvalve.htm It's about discharge instead of filling Here's the paper http://www2.dem.uc.pt/antonio.gameir...SEAS_paper.pdf I think it may give you some ideas about meshes and time steps Rui

 May 30, 2007, 08:15 Re: Help with large sim #5 Gert-Jan Guest   Posts: n/a Why do you do this transient CFD-calculation? Do you really need to know the full history of the filling of the vessel? Isn't it sufficient to create a mesh for the 30% fill and perform the stationary flow study with different inlet angles and inlet velocities? I don't think the situation at 5% filling ratio will influence the situation at 30%, unless you want to solve complex chemical reactions that are competitive. If you have to solve that......... Gert-Jan

 May 30, 2007, 08:57 Re: Help with large sim #6 stu Guest   Posts: n/a Can I use the Step function in CEL to change the timestep each of the 10% full domains runs? eg initially start the second doamin which represents 10-20% Height at a long 1 minute time step, but when I want to turn it on, I use the step function to change the time step to 0.25 seconds, which ios the same as the 0-10% height domain? That was I would not have to calculate what the air is doing in a much large all encompassing domain. Would this work for a transient analysis? Thanks Stu

 May 30, 2007, 13:38 Re: Help with large sim #7 Gert-Jan Guest   Posts: n/a What you can do is create a flat cilinder which represents the first 10% of your vessel. Using dynamic meshing, you can let this grow with the pace of the amount of water. When it is 20%, regrid your domain, interpolate the previous solution and let it grow further to say 40% ... and so on. You can represent the free surface as a wall with free slip. The pressure on this surface is a rough guess for the height of the disturbances. This is a possible route but I still have my thoughts if this CFD-simulation is useful...... It won't be my approach. Good luck, Gert-Jan www.bunova.nl

 June 4, 2007, 17:13 Re: Help with large sim #8 Lee Axon (Point Zero Consulting Ltd) Guest   Posts: n/a Hi Stu, I offer a low cost processing only service for CFX simulations: http://www.pointzeroconsulting.co.uk...rocessing.html Drop me a mail if interested. Cheers, Lee.

 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 evrikon OpenFOAM Post-Processing 28 June 28, 2016 03:43 djbungee OpenFOAM Programming & Development 45 March 23, 2015 05:14 comb Main CFD Forum 0 February 8, 2011 07:21 Alejandra Menchaca Phoenics 0 March 3, 2009 20:53 Bo Jensen Siemens 12 February 20, 2003 00:31

All times are GMT -4. The time now is 15:22.