[Robreid]

Hey
For my thesis i am looking at 2d modelling of a vertical axis marine turbine. I have had some experience using gambit and fluent but i am struggling with the rotating mesh part of the problem setup. the setup should look like the image below



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the issue i am having is setting up the boundary conditions to allow for the rotational grid.

any assistance that could be offered would be appreciated

Thanks

[isabel]

Hello Robreid,

I think the easiest way in Fluent is to define all the mesh as fixed grid, and impose the rotation to the blades. With this procedure, Fluent updates the mesh after each time step and rotates the blades around the axis.

[saclu]

Hi,
According to the setup you gave us, 2 interfaces have to be defined between your moving zones and your stationary zone..did you do that properly ?
do you want the turbine to have a specific agular velocity or to be free in the fluid?

PS: I have the same simulations to do for my phD...may be it would be nice to keep in touch, we would probably meet the same problems.

[Robreid]

@saclu

hey thanks for the advice i managed to get the interfaces defined with some assistance from someone in my university department.

the turbine is going to have a specific angular velocity and im going to look at the tip speed ratio as my variable.

i have gone from one problem to the next sadly. im now coming up with the following error message

Warning: non-positive volumes exist.
Primitive Error at Node 0: Update-Dynamic-Mesh failed. Negative cell volume detected.
Primitive Error at Node 1: Update-Dynamic-Mesh failed. Negative cell volume detected.
Error: Update-Dynamic-Mesh failed. Negative cell volume detected.
Error Object: #f

any ideas ? will have a look around the forum for anyone else that had problems with this but i thought id ask here first.

[saclu]

Ok, what version of fluent are you using and how did you set up the motion?

[Robreid]

its the newest version of fluent and gambit 2.4.6 i am using

the .msh .dbs and .cas files are in the following folder if you would like to have a look

http://www.mediafire.com/?8nrukf6i0t22san

if you run the case file as it is you will see the error

[saclu]

Hi,
I had a look to your file. The set up seems good to me. However the mesh in conformal, I think there is something wrong with that. The mesh on each side of the interface should'nt share the same node. I would suggest you work on it.
Good luck