Near-wall turbulence correction

tarjeivs · February 18, 2021, 07:37

Particle deposition is very dependent on the normal fluctuating velocity (v'). Higher fluctuating velocity enhances particle deposition. Therefore I have implemented the anisotropic RSM for a straight channel flow with enhanced wall function. However, the normal fluctuating velocity still deviates from the DNS results in the vicinity of the wall.

Aim: to correct the normal fluctuating velocity for y+<4.

I want to define a UDF for y+<4 for v' along the channel walls based on DNS data. Is this possible to achieve in Fluent 2020 R2? What UDF-macro can be used?

I believe another alternative is to define the three fluctuating components along the channel wall for y+<30 (or more) using the DEFINE_WALL_FUNCTION? This seems complicated if I, in addition, have to code the enhanced wall treatment for RSM for velocity, k, and epsilon in the UDF.

Do you have any other suggestions?

zahrae · October 19, 2021, 07:24

hello Sir!
I am facing the same problem, and I don't have any idea about which macro I need to use to change the fluctuations !!
can you please give me some guidelines !
Thanks in advance.
Regards.

tarjeivs · November 14, 2021, 15:44

Hi, zahrae!

I implemented a boundary layer model for the wall-normal mean fluctuating velocity as input to the discrete phase model, e.g. the particle drag force. The code and my method is described in my Master's thesis Particle Deposition From Geothermal Supercritical Steam:

https://ntnuopen.ntnu.no/ntnu-xmlui/...e-attribute=en

Best regards,
Tarjei Vefring Stordal

zahrae · November 14, 2021, 16:14

Thank you for your reply!
Best regards.

February 18, 2021, 07:37	Near-wall turbulence correction	#1
tarjeivs New Member Join Date: Nov 2020 Posts: 3 Rep Power: 5	Particle deposition is very dependent on the normal fluctuating velocity (v'). Higher fluctuating velocity enhances particle deposition. Therefore I have implemented the anisotropic RSM for a straight channel flow with enhanced wall function. However, the normal fluctuating velocity still deviates from the DNS results in the vicinity of the wall. Aim: to correct the normal fluctuating velocity for y+<4. I want to define a UDF for y+<4 for v' along the channel walls based on DNS data. Is this possible to achieve in Fluent 2020 R2? What UDF-macro can be used? I believe another alternative is to define the three fluctuating components along the channel wall for y+<30 (or more) using the DEFINE_WALL_FUNCTION? This seems complicated if I, in addition, have to code the enhanced wall treatment for RSM for velocity, k, and epsilon in the UDF. Do you have any other suggestions?

November 14, 2021, 15:44	An alternative solution to near-wall turbulence correction	#3
tarjeivs New Member Join Date: Nov 2020 Posts: 3 Rep Power: 5	Hi, zahrae! I implemented a boundary layer model for the wall-normal mean fluctuating velocity as input to the discrete phase model, e.g. the particle drag force. The code and my method is described in my Master's thesis Particle Deposition From Geothermal Supercritical Steam: https://ntnuopen.ntnu.no/ntnu-xmlui/...e-attribute=en Best regards, Tarjei Vefring Stordal

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October 19, 2021, 07:24		#2
zahrae Member imane Join Date: Aug 2018 Posts: 62 Rep Power: 7	hello Sir! I am facing the same problem, and I don't have any idea about which macro I need to use to change the fluctuations !! can you please give me some guidelines ! Thanks in advance. Regards.

November 14, 2021, 16:14		#4
zahrae Member imane Join Date: Aug 2018 Posts: 62 Rep Power: 7	Thank you for your reply! Best regards.