Help with choosing a viscosity model

xTamx420 · June 23, 2011, 12:02

Hi, I am trying to model a sort of extended foil shape 2D section and I would like to get a second opinion on the setup. The shape is a narrow rectangular section with the leading edge of a NACA foil on the front and the trailing edge on the back.

The flow is moving at 0.5 m/s with no angle of attack and the reynolds number is around 415000. I chose laminar flow for the simulation but I got some results that were unexpected. I think it is either because of vortex induced vibration or I chose the wrong viscosity model.

The mesh has more than 300000 elements and is a C-shaped mesh.

Any comments on this setup and model choice would be appreciated.

AdrienL · July 1, 2011, 11:42

Hi,

the best for an airfoil profil in Fluent is to do the geometry as shown in the picture and use a far field fonction on the outside.
You should also think about adding prism layer (3 would be enough) around the airfoil and use a k epsilon realizable with enhanced wall treatment viscosity model

sincerly

Adrien

xTamx420 · July 4, 2011, 09:42

According to the reynolds number the flow wont be fully turbulent, which is why I close laminar flow. Are you saying it will be turbulent?

Tom

AdrienL · July 4, 2011, 11:07

Yes, it will be turbulent because the velocity will increase near the naca profil.
So you should use a k epsilon model (or spalart allmaras if the computing is too slow).

xTamx420 · July 4, 2011, 12:05

Right, I forgot about that. I will give your suggestion a try then. One question though, what do you mean by a prism layer?

AdrienL · July 4, 2011, 17:09

I mean the cells that will enable you to get the boundary layer

June 23, 2011, 12:02	Help with choosing a viscosity model	#1
xTamx420 New Member Tom Join Date: May 2011 Posts: 14 Rep Power: 14	Hi, I am trying to model a sort of extended foil shape 2D section and I would like to get a second opinion on the setup. The shape is a narrow rectangular section with the leading edge of a NACA foil on the front and the trailing edge on the back. The flow is moving at 0.5 m/s with no angle of attack and the reynolds number is around 415000. I chose laminar flow for the simulation but I got some results that were unexpected. I think it is either because of vortex induced vibration or I chose the wrong viscosity model. The mesh has more than 300000 elements and is a C-shaped mesh. Any comments on this setup and model choice would be appreciated. ava likes this.

July 4, 2011, 11:07		#4
AdrienL Member Adrien Lemoine Join Date: Jun 2011 Location: Paris,France Posts: 31 Rep Power: 14	Yes, it will be turbulent because the velocity will increase near the naca profil. So you should use a k epsilon model (or spalart allmaras if the computing is too slow). __________________ ------------------------------------------- Plz add reputation if the answer is correct A cœur vaillant rien d'impossible ------------------------------------------

July 4, 2011, 17:09		#6
AdrienL Member Adrien Lemoine Join Date: Jun 2011 Location: Paris,France Posts: 31 Rep Power: 14	I mean the cells that will enable you to get the boundary layer __________________ ------------------------------------------- Plz add reputation if the answer is correct A cœur vaillant rien d'impossible ------------------------------------------

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July 4, 2011, 09:42		#3
xTamx420 New Member Tom Join Date: May 2011 Posts: 14 Rep Power: 14	According to the reynolds number the flow wont be fully turbulent, which is why I close laminar flow. Are you saying it will be turbulent? Tom

July 4, 2011, 12:05		#5
xTamx420 New Member Tom Join Date: May 2011 Posts: 14 Rep Power: 14	Right, I forgot about that. I will give your suggestion a try then. One question though, what do you mean by a prism layer?