CFD Online Logo CFD Online URL
Home > Forums > Main CFD Forum

VAWT mesh in gambit

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   January 13, 2009, 13:13
Default VAWT mesh in gambit
Posts: n/a

i'm trying to do a simulation with fluent of a wind turbine with vertical axis. It's a H-Darrieus-Rotor. I've done a 2d mesh with the section of the 4 blades. They're in a circular face, set as rotating face.

The problem is that the results give a poor momentum, and I think it is because it doesn't calculate the momentum of the lift force, just the momentum of the drag force.

Can anyone help me?

Thank you very much
  Reply With Quote

Old   January 16, 2009, 01:52
Default Re: VAWT mesh in gambit
Bikini Girl with Machinegun
Posts: n/a
At what tipspeed ratio does it give poor results? VAWT have known problems at TSR around 1.

Does Fluent automatically include dynamic stall effects which are known to be important for VAWT. (For example, the angles of attack can change from -180 to 180 degrees at TSR=1).

Incidentally, why are you using 4 blades? High solidity means that you might be sacrificing a lot of efficiency to get high starting torque (if that's the reason for going to 4 blades instead of 3).

  Reply With Quote

Old   January 17, 2009, 13:23
Default Re: VAWT mesh in gambit
Posts: n/a
it actually gives poor results at every TSR i've tried so far.

I'm doing this as my final project for my degree, and the aim is to try different combinations with different type of blades, angle and number of blades. We have prepared a progam in Delphi that allows us to start the simulation at one TSR and when it's finished, it starts automatically another one, so that in the end we have the whole efficiency curve. And by now all the results have been very dissapointing.

About the dynamic stall effects, i don't now if Fluent automatically includes them.

Thanks for your answer. Jonathan
  Reply With Quote

Old   January 19, 2009, 15:00
Default Re: VAWT mesh in gambit
Posts: n/a
Hi Jonathan,

what method are you using to solve the multiple frame of reference problem...sliding mesh or MRF?

What makes you think that lift forces are not calculated? In general in aerodynamic problems the lift force is larger and easier to calculate accurately.

So, I am a bit surprised that Fluent has not calculated this appropriately?

What is your meshing strategy?

Give us some more details and maybe we can help.


  Reply With Quote

Old   January 22, 2009, 09:18
Default Re: VAWT mesh in gambit
Posts: n/a
The way i'm doing it is the following:

there's a circular area with centre in 0,0. to this circular area i substrac the areas of the blades and set it as a sliding mesh.

there's a bigger area with a square form. in the middle of this, i substract a circle as big as the other area. i set it as a stationary area.

in this second area i set the link site as velocity inlet and the other three as pressure outup. but i think i should set the link, upper and lower sites as velocity input and only the right site as pressure output (i'm not very sure of this though)

then in the calculation the rotational speed of the sliding mesh is changed several times so i get the whole efficiency curve.

for the viscous flowing, i select k-epsylon.

the solver is set as segregatec, implicit, unsteady and 2nd order implicit.

with these settings, i've tried a savonius rotor and the results are not bad. That's why i thought that the problem appears when calculating the lift force momentum.

Hope anyone can help.

  Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Mesh motion with Translation & Rotation Doginal CFX 2 January 12, 2014 07:21
snappyHexMesh won't work - zeros everywhere! sc298 OpenFOAM Native Meshers: snappyHexMesh and Others 2 March 27, 2011 21:11
Convergence moving mesh lr103476 OpenFOAM Running, Solving & CFD 30 November 19, 2007 15:09
How to mesh a circle by Gambit? Zhengcai Ye FLUENT 5 March 24, 2006 02:04
Mesh import from gambit Kaushik Balakrishnan (Balakrishnan) OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 5 April 21, 2005 13:42

All times are GMT -4. The time now is 22:11.