Turbulence and Laminar model for empty narrow chan

October 4, 2004, 04:04

To CFD experts,

i am simulating the flow of a fluid in a narrow channel. I am sure this narrow channel will generate laminar flow since it is empty and Re < 1000. However, when i tried to simulate under laminar /turbulence(k-e) model, it gives different answer in term of velocity distribution for both models. May i know what makes this different ?

Thank you..

From KKLAU

October 4, 2004, 07:49

Normal k-e turbulence inherently assumes that the Reynolds number is high and the flow is fully turbulent. That is, it can't simulate either laminar flow or transition. If you switch k-e on numerically, then it will generate turbulent viscosity and thereby additional diffusion, leading to a different solution from laminar one. There are low-reynolds number version of k-e which may performance better.

October 4, 2004, 22:51

To fluent experts:

How can i set k-e model for low Reynolds number? Is it same with the k-e RNG model????

From

KKLAU

October 5, 2004, 02:35

USE ENHANCED WALL TREATMENT OPTION

October 5, 2004, 04:11

Enhanced wall treatment use to resolve viscous sub layaer so u have to be care ful for y plus values in ur calculation

October 18, 2004, 17:36

now i have found something new

to use the ke with low Re number use this command

/define/models/viscous/turbulence-expert> low-re-ke Enable the low-Re k-epsilon turbulence model? [no] yes

this will help u i hope

regards

October 4, 2004, 04:04	Turbulence and Laminar model for empty narrow chan	#1
KKLAU Guest Posts: n/a	To CFD experts, i am simulating the flow of a fluid in a narrow channel. I am sure this narrow channel will generate laminar flow since it is empty and Re < 1000. However, when i tried to simulate under laminar /turbulence(k-e) model, it gives different answer in term of velocity distribution for both models. May i know what makes this different ? Thank you.. From KKLAU

October 4, 2004, 07:49	Re: Turbulence and Laminar model for empty narrow	#2
John Luo Guest Posts: n/a	Normal k-e turbulence inherently assumes that the Reynolds number is high and the flow is fully turbulent. That is, it can't simulate either laminar flow or transition. If you switch k-e on numerically, then it will generate turbulent viscosity and thereby additional diffusion, leading to a different solution from laminar one. There are low-reynolds number version of k-e which may performance better.

October 4, 2004, 22:51	How can i set k-e model for low Re??	#3
KKLAU Guest Posts: n/a	To fluent experts: How can i set k-e model for low Reynolds number? Is it same with the k-e RNG model???? From KKLAU

October 5, 2004, 02:35	Re: How can i set k-e model for low Re??	#4
SAM Guest Posts: n/a	USE ENHANCED WALL TREATMENT OPTION

October 5, 2004, 04:11	Re: How can i set k-e model for low Re??	#5
SAM Guest Posts: n/a	Enhanced wall treatment use to resolve viscous sub layaer so u have to be care ful for y plus values in ur calculation

October 18, 2004, 17:36	Re: How can i set k-e model for low Re??	#6
SAM Guest Posts: n/a	now i have found something new to use the ke with low Re number use this command /define/models/viscous/turbulence-expert> low-re-ke Enable the low-Re k-epsilon turbulence model? [no] yes this will help u i hope regards

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