Transition Models Help

paulnardone · September 22, 2011, 15:57

hello folks out there in cd-adapco land.

My name is Paul and I'm working on my graduate research project. The basic Idea behind this project is to model "Bypass" transition along a flat plate (the plate being similar to a turbine blade).

I know there are 2 transition models in the Star-CCM+ product which are

1. The Gamma Re-Theta model, and
2. The Turbulence Suppression model.

Does anyone have any advice on which of these to use or are they both useless for this case since such a transition is not typical. (hence why we are studying it). I'm able to get them both to work but I'm not sure if they are outputting the correct answers yet.

Beyond this if any one out there has experience with modeling Transition especially "bypass" transition feel free to contact me with information.

thank you

Paul Nardone Jr
University of Idaho, Idaho Falls
Nuclear Engineering Department
paulnardonejr@gmail.com

abdul099 · September 22, 2011, 17:45

I'm not sure what you mean by "Bypass transition". But for the Gamm Re Theta model, you will need a huge number of prism layers.

Regarding to the user guide, the turbulence suppresion model is not a true transition model:
"The Turbulence Suppression model allows the user to mimic the effect of transition by suppressing the turbulence in a certain pre-defined region. Since it does not have a predictive capability, it is arguably not a true transition model."
Should be self-explaining.

paulnardone · September 22, 2011, 19:16

Hey thanks for your response. I assumed that the turb. suppression was no good as you mentioned because it wasn't a true transition model.

I'm currently running a Gamma Re Theta model and I did apply a more significant prism layer... 30 layers over a 2 cm boundry layer with a 1.2 cell growth rate. I'm running my model locally with 8-gigs or ram so I didnt want to go too crazy with the mesh (700,000 cells currently)... but my solution blew up... so I think I need to adapt my mesh and a few other parameters.

when I said "bypass" transition I meant that transition from a laminar to turbulent state is prematurely onset primarily due to strong free stream turbulence...

it's definitely a doosie of a problem for me

thanks again for your response and if you have any more advice on the matter I'll definitely take it into consideration

Paul

September 22, 2011, 15:57	Transition Models Help	#1
paulnardone New Member Paul Nardone Join Date: Sep 2011 Location: Lawrence KS Posts: 3 Rep Power: 14	hello folks out there in cd-adapco land. My name is Paul and I'm working on my graduate research project. The basic Idea behind this project is to model "Bypass" transition along a flat plate (the plate being similar to a turbine blade). I know there are 2 transition models in the Star-CCM+ product which are 1. The Gamma Re-Theta model, and 2. The Turbulence Suppression model. Does anyone have any advice on which of these to use or are they both useless for this case since such a transition is not typical. (hence why we are studying it). I'm able to get them both to work but I'm not sure if they are outputting the correct answers yet. Beyond this if any one out there has experience with modeling Transition especially "bypass" transition feel free to contact me with information. thank you Paul Nardone Jr University of Idaho, Idaho Falls Nuclear Engineering Department paulnardonejr@gmail.com

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Transition Turbulence Models	Apurva	Main CFD Forum	3	September 7, 2018 05:48
Ansys 12, Fluent, SST Transition models	bugra	FLUENT	9	February 8, 2016 01:57
Issue with transition models	k.vimalakanthan	CFX	1	April 26, 2011 22:15
Fluent 12.1 - transition viscous models	kdrbrk	FLUENT	4	July 29, 2010 11:34
Code release: Flow Transition and Turbulence	Chaoqun Liu	Main CFD Forum	0	September 26, 2008 17:15

September 22, 2011, 17:45		#2
abdul099 Senior Member Join Date: Oct 2009 Location: Germany Posts: 636 Rep Power: 21	I'm not sure what you mean by "Bypass transition". But for the Gamm Re Theta model, you will need a huge number of prism layers. Regarding to the user guide, the turbulence suppresion model is not a true transition model: "The Turbulence Suppression model allows the user to mimic the effect of transition by suppressing the turbulence in a certain pre-defined region. Since it does not have a predictive capability, it is arguably not a true transition model." Should be self-explaining.

September 22, 2011, 19:16		#3
paulnardone New Member Paul Nardone Join Date: Sep 2011 Location: Lawrence KS Posts: 3 Rep Power: 14	Hey thanks for your response. I assumed that the turb. suppression was no good as you mentioned because it wasn't a true transition model. I'm currently running a Gamma Re Theta model and I did apply a more significant prism layer... 30 layers over a 2 cm boundry layer with a 1.2 cell growth rate. I'm running my model locally with 8-gigs or ram so I didnt want to go too crazy with the mesh (700,000 cells currently)... but my solution blew up... so I think I need to adapt my mesh and a few other parameters. when I said "bypass" transition I meant that transition from a laminar to turbulent state is prematurely onset primarily due to strong free stream turbulence... it's definitely a doosie of a problem for me thanks again for your response and if you have any more advice on the matter I'll definitely take it into consideration Paul