non reflecting version of Navier Stokes characteristic boundary condition

Weiqiang Liu · June 12, 2020, 23:39

Hi all,

I tried to reproduce results in a paper and found the boundary condition setting which is described by the author like follows:

"For inflow and outflow boundary conditions ,a non reflecting version of Navier Stokes characteristic boundary condition is applied"

I am wondering what is non reflecting version of Navier Stokes characteristic boundary condition? How can I implement it in fluent?

Best regards

Weiqiang

LuckyTran · June 14, 2020, 09:17

These are boundary conditions for preventing unwanted reflection of acoustic waves at boundaries. See Pointsot and Lele and Kim and Lee. When running transient compressible flow calculations, acoustic waves can build up inside the domain and eventually trigger an acoustic mode because the normal inlet and outlet BC's are acoustically reflecting.

Note that Fluent already has a wave transmissive boundary condition which is designed for the same purpose.

Weiqiang Liu · June 14, 2020, 10:03

Quote:

Originally Posted by LuckyTran

These are boundary conditions for preventing unwanted reflection of acoustic waves at boundaries. See Pointsot and Lele and Kim and Lee. When running transient compressible flow calculations, acoustic waves can build up inside the domain and eventually trigger an acoustic mode because the normal inlet and outlet BC's are acoustically reflecting.

Note that Fluent already has a wave transmissive boundary condition which is designed for the same purpose.

Hi,

Thanks for your answer!

Best

weiqiang

June 12, 2020, 23:39	non reflecting version of Navier Stokes characteristic boundary condition	#1
Weiqiang Liu Senior Member Weiqiang Liu Join Date: Feb 2018 Posts: 278 Rep Power: 9	Hi all, I tried to reproduce results in a paper and found the boundary condition setting which is described by the author like follows: "For inflow and outflow boundary conditions ,a non reflecting version of Navier Stokes characteristic boundary condition is applied" I am wondering what is non reflecting version of Navier Stokes characteristic boundary condition? How can I implement it in fluent? Best regards Weiqiang

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June 14, 2020, 09:17		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,674 Rep Power: 66	These are boundary conditions for preventing unwanted reflection of acoustic waves at boundaries. See Pointsot and Lele and Kim and Lee. When running transient compressible flow calculations, acoustic waves can build up inside the domain and eventually trigger an acoustic mode because the normal inlet and outlet BC's are acoustically reflecting. Note that Fluent already has a wave transmissive boundary condition which is designed for the same purpose.