LES for diesel engine

kazuki · November 12, 2018, 04:52

I examine in-cylinder gas flow of diesel engine with RANS model. However, I want to use LES model for improvement of accuracy. Please tell me what kind of LES model do you use for calculation of diesel engine.

alireza.mashayekh · November 13, 2018, 10:39

There are a few models implemented in CONVERGE for LES modeling. The first that we try is the DYNAMIC STRUCTURE model.
Please note that if you run your case w/ LES models but w/ the grid sized recommended for RANS simulations, your burning would be much slower; so, you have to significantly refine the mesh to get proper results w/ the LES models.

Best,

kazuki · November 14, 2018, 21:18

Thank you for your advice. I apply 3 mm as based grid size when I use RANS model. How much should I decrease order of based grid size, when I use LES model.

Best regards

alireza.mashayekh · November 15, 2018, 10:47

We have not done a grid convergence study for LES models in engine simulations. We know that for sprays, LES models converge around 62.5 um, but using such a fine mesh in an engine would make the simulation very expensive.
So, it is up to you to run some cases and see at what grid size you get proper results.

Best,

kazuki · November 16, 2018, 22:58

I appreciate your comment. I'll try to do that.

November 12, 2018, 04:52	LES for diesel engine	#1
kazuki New Member kazuki Join Date: Jan 2017 Posts: 5 Rep Power: 9	I examine in-cylinder gas flow of diesel engine with RANS model. However, I want to use LES model for improvement of accuracy. Please tell me what kind of LES model do you use for calculation of diesel engine. Last edited by kazuki; November 13, 2018 at 00:24.

November 13, 2018, 10:39		#2
alireza.mashayekh New Member Alireza Mashayekh Join Date: Aug 2017 Location: Convergent Science, Madison WI Posts: 14 Rep Power: 9	There are a few models implemented in CONVERGE for LES modeling. The first that we try is the DYNAMIC STRUCTURE model. Please note that if you run your case w/ LES models but w/ the grid sized recommended for RANS simulations, your burning would be much slower; so, you have to significantly refine the mesh to get proper results w/ the LES models. Best, __________________ Alireza Mashayekh Senior Research Engineer, Applications CONVERGECFD

November 15, 2018, 10:47		#4
alireza.mashayekh New Member Alireza Mashayekh Join Date: Aug 2017 Location: Convergent Science, Madison WI Posts: 14 Rep Power: 9	We have not done a grid convergence study for LES models in engine simulations. We know that for sprays, LES models converge around 62.5 um, but using such a fine mesh in an engine would make the simulation very expensive. So, it is up to you to run some cases and see at what grid size you get proper results. Best, mohsinmkhan likes this. __________________ Alireza Mashayekh Senior Research Engineer, Applications CONVERGECFD

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November 14, 2018, 21:18		#3
kazuki New Member kazuki Join Date: Jan 2017 Posts: 5 Rep Power: 9	Thank you for your advice. I apply 3 mm as based grid size when I use RANS model. How much should I decrease order of based grid size, when I use LES model. Best regards

November 16, 2018, 22:58		#5
kazuki New Member kazuki Join Date: Jan 2017 Posts: 5 Rep Power: 9	I appreciate your comment. I'll try to do that.