Fully developed flow inlet

Pleb · November 22, 2011, 11:29

Hi, I am having major problems creating a fully developed flow inlet condition.

I am modelling a straight pipe using LES. I am trying to use the outlet boundary from this sim as the inlet for another sim. I have attempted to use tables but no luck as i need the inlet to vary with time (turbulent flow). The exported table with time will not import directly to the inlet as the table is set out incorrectly!
Ideally i need a sythetic fully turbulent inlet condition like fluent but this doesnt seem to exist in Star!

Any ideas welcome

Thanks!

kyle · November 22, 2011, 12:57

Are you trying to run these two simulations at the same time or using one to generate the boundary conditions for the other?

Either way, this can be done with tables. You just need to use a macro to update the tables that is run every timestep.

If you are running both simulations at the same time, there is also the Co-simulation feature. I have not used it.

abdul099 · November 23, 2011, 15:54

I would do a co-simulation approach. Have a look to the user guide, search for "Data Mapper".

Pleb · November 24, 2011, 10:56

Oooo okay thanks for the replies.

The co simulation sounds interesting but no, i want to use the results from the straight pipe for the resonator sim.

Hmmm i have not used a macro before. So I should set up a macro to export and import an xyz table each time step? Does that mean i need to run the straight pipe for at least the amount of time i want to run the resonator sim for? Can I instead have tables for, say 500 timesteps and run them on a loop to create a rough synthetic turb flow?

Thanks!

kyle · November 24, 2011, 11:57

This is not going to be all that simple. You are likely going to need to write two macros. The first macro would have to run the pipe simulation and export a table each timestep. The second macro would run the second simulation and read in the corresponding table for each timestep.

You may be able to keep the number of files and disk space down by exporting a portion of the solution to a single .CCM file instead of thousands of tables. This would require using data mappers instead of tables. I have only used this to map steady state surface temperatures so I don't know how well it would work.

Pleb · November 25, 2011, 11:25

Thanks for you're help Kyle, much appreciated.
Looks like fun times are in store for me! :/

Surely there is more straight forward way for this. I can import a table (time) for the inlet. I just need to be able to export a table with xyz time with the correct format :s

I may still look into co simulation. Any other ideas welcome!

Thanks

November 22, 2011, 11:29	Fully developed flow inlet	#1
Pleb New Member Imran Join Date: Oct 2010 Posts: 9 Rep Power: 15	Hi, I am having major problems creating a fully developed flow inlet condition. I am modelling a straight pipe using LES. I am trying to use the outlet boundary from this sim as the inlet for another sim. I have attempted to use tables but no luck as i need the inlet to vary with time (turbulent flow). The exported table with time will not import directly to the inlet as the table is set out incorrectly! Ideally i need a sythetic fully turbulent inlet condition like fluent but this doesnt seem to exist in Star! Any ideas welcome Thanks!

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November 22, 2011, 12:57		#2
kyle Senior Member Join Date: Mar 2009 Location: Austin, TX Posts: 160 Rep Power: 18	Are you trying to run these two simulations at the same time or using one to generate the boundary conditions for the other? Either way, this can be done with tables. You just need to use a macro to update the tables that is run every timestep. If you are running both simulations at the same time, there is also the Co-simulation feature. I have not used it.

November 23, 2011, 15:54		#3
abdul099 Senior Member Join Date: Oct 2009 Location: Germany Posts: 636 Rep Power: 21	I would do a co-simulation approach. Have a look to the user guide, search for "Data Mapper".

November 24, 2011, 10:56		#4
Pleb New Member Imran Join Date: Oct 2010 Posts: 9 Rep Power: 15	Oooo okay thanks for the replies. The co simulation sounds interesting but no, i want to use the results from the straight pipe for the resonator sim. Hmmm i have not used a macro before. So I should set up a macro to export and import an xyz table each time step? Does that mean i need to run the straight pipe for at least the amount of time i want to run the resonator sim for? Can I instead have tables for, say 500 timesteps and run them on a loop to create a rough synthetic turb flow? Thanks!

November 24, 2011, 11:57		#5
kyle Senior Member Join Date: Mar 2009 Location: Austin, TX Posts: 160 Rep Power: 18	This is not going to be all that simple. You are likely going to need to write two macros. The first macro would have to run the pipe simulation and export a table each timestep. The second macro would run the second simulation and read in the corresponding table for each timestep. You may be able to keep the number of files and disk space down by exporting a portion of the solution to a single .CCM file instead of thousands of tables. This would require using data mappers instead of tables. I have only used this to map steady state surface temperatures so I don't know how well it would work.

November 25, 2011, 11:25		#6
Pleb New Member Imran Join Date: Oct 2010 Posts: 9 Rep Power: 15	Thanks for you're help Kyle, much appreciated. Looks like fun times are in store for me! :/ Surely there is more straight forward way for this. I can import a table (time) for the inlet. I just need to be able to export a table with xyz time with the correct format :s I may still look into co simulation. Any other ideas welcome! Thanks