Modeling a thin sail in Fluent

ziggo · February 15, 2013, 09:03

I am trying to model a tetrahedral kite in CFD.
The model only consists of the sails, the aerodynamic influence of the frame is neglected.
To get started I'm now only trying to model one cell of the tetrahedral kite, so only two sails.

As the sail material is very thin I am wondering how to model this geometry for use in Fluent. The only way I can think of right now is a flat plate with a thickness to chord ratio of around 0.05%. However, this will require very fine meshing to capture the small thickness of the edges of the sail.
Is there some best practice to model thin sails?

diamondx · February 16, 2013, 08:38

Did you figure out how to solve your problem ????

ziggo · February 16, 2013, 09:34

No, unfortunately not. I'm still hoping someone here might know how to model this.

diamondx · February 16, 2013, 14:42

if what you want is a really really thin sail then you are talking about surface. zero thickness. you can do that in every CAD program, go with designmodeler.
create points or edges, then create a surface from those edges, for the surrounding fluid, you will have to create a body like a sphere or square around that surface.

ziggo · February 16, 2013, 15:49

And after that do I just proceed modelling as if I have a solid? So I would make an enclosure around the surface and then perform a boolean operation subtracting the surface from the enclosure body?

victoryv · February 16, 2013, 18:19

make a surface of the sail in designmodeler. Draw an enclosure around it . Use boolean op to subtract the volume. Change the volume to fluid. Mesh and solve. BASIC STEPS.

ziggo · March 14, 2013, 09:57

I have made a surface, drawn an enclosure around it but I could not perform a subtract boolean operation on the enclosure as this would create a non-manifold geometry. How do I subtract the zero-thickness sail from the volume? Or do I subtract it at all?

stuart23 · March 14, 2013, 19:02

Bart,

If you are using Ansys DM, there is no need to do the boolean.Just select all the parts (fluid body and surfaces) in the object tree on the left side of the screen, right-click, and choose Form New Part.

This approach allows you to have surfaces "floating" in a solid.

Stu

Bdew8556 · May 31, 2013, 23:43

Hey guys

Does anyone know how to attach the base of a fin/sail to one side of the enclosure? ie cushion value = 0

Cheers

Brett

stuart23 · June 2, 2013, 22:27

Brett,

Not sure what you mean, does your geometry have a thin wall attaching to a wall (like a baffle)?

Stu

Bdew8556 · June 2, 2013, 23:43

Hey Stu,

im essentially wanting to join the base of a solid to one face of a flow enclosure. Does that make more sense?

Brett

February 15, 2013, 09:03	Modeling a thin sail in Fluent	#1
ziggo Member Bart A. Join Date: Feb 2012 Posts: 45 Rep Power: 0	I am trying to model a tetrahedral kite in CFD. The model only consists of the sails, the aerodynamic influence of the frame is neglected. To get started I'm now only trying to model one cell of the tetrahedral kite, so only two sails. As the sail material is very thin I am wondering how to model this geometry for use in Fluent. The only way I can think of right now is a flat plate with a thickness to chord ratio of around 0.05%. However, this will require very fine meshing to capture the small thickness of the edges of the sail. Is there some best practice to model thin sails?

February 16, 2013, 08:38		#2
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 29	Did you figure out how to solve your problem ???? __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

February 16, 2013, 14:42		#4
diamondx Super Moderator Ghazlani M. Ali Join Date: May 2011 Location: Tokyo, Japan Posts: 1,385 Blog Entries: 23 Rep Power: 29	if what you want is a really really thin sail then you are talking about surface. zero thickness. you can do that in every CAD program, go with designmodeler. create points or edges, then create a surface from those edges, for the surrounding fluid, you will have to create a body like a sphere or square around that surface. __________________ Regards, New to ICEM CFD, try this document --> https://goo.gl/KAOIwm Ali

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February 16, 2013, 09:34		#3
ziggo Member Bart A. Join Date: Feb 2012 Posts: 45 Rep Power: 0	No, unfortunately not. I'm still hoping someone here might know how to model this.

February 16, 2013, 15:49		#5
ziggo Member Bart A. Join Date: Feb 2012 Posts: 45 Rep Power: 0	And after that do I just proceed modelling as if I have a solid? So I would make an enclosure around the surface and then perform a boolean operation subtracting the surface from the enclosure body?

February 16, 2013, 18:19		#6
victoryv Member Join Date: Sep 2012 Location: FL Posts: 79 Rep Power: 14	make a surface of the sail in designmodeler. Draw an enclosure around it . Use boolean op to subtract the volume. Change the volume to fluid. Mesh and solve. BASIC STEPS.

March 14, 2013, 09:57		#7
ziggo Member Bart A. Join Date: Feb 2012 Posts: 45 Rep Power: 0	I have made a surface, drawn an enclosure around it but I could not perform a subtract boolean operation on the enclosure as this would create a non-manifold geometry. How do I subtract the zero-thickness sail from the volume? Or do I subtract it at all?

March 14, 2013, 19:02		#8
stuart23 Senior Member Stuart Buckingham Join Date: May 2010 Location: United Kingdom Posts: 267 Rep Power: 26	Bart, If you are using Ansys DM, there is no need to do the boolean.Just select all the parts (fluid body and surfaces) in the object tree on the left side of the screen, right-click, and choose Form New Part. This approach allows you to have surfaces "floating" in a solid. Stu

May 31, 2013, 23:43		#9
Bdew8556 Senior Member Brett Join Date: May 2013 Posts: 212 Rep Power: 14	Hey guys Does anyone know how to attach the base of a fin/sail to one side of the enclosure? ie cushion value = 0 Cheers Brett

June 2, 2013, 22:27		#10
stuart23 Senior Member Stuart Buckingham Join Date: May 2010 Location: United Kingdom Posts: 267 Rep Power: 26	Brett, Not sure what you mean, does your geometry have a thin wall attaching to a wall (like a baffle)? Stu

June 2, 2013, 23:43		#11
Bdew8556 Senior Member Brett Join Date: May 2013 Posts: 212 Rep Power: 14	Hey Stu, im essentially wanting to join the base of a solid to one face of a flow enclosure. Does that make more sense? Brett