CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   ANSYS (http://www.cfd-online.com/Forums/ansys/)
-   -   Vortex Rings in FLUENT? (http://www.cfd-online.com/Forums/ansys/84171-vortex-rings-fluent.html)

nha1g08 January 21, 2011 18:14

Vortex Rings in FLUENT?
 
Hello I am looking to simulate vortex rings in FLUENT.
I want to know if this is possible, because most simulations are done using CFD code.
I want to achieve three thing on FLUENT.
1. Simulate a normal vortex ring moving.
2. Simulate two vortex rings colliding.
3. Simulation of leapfrogging of vortex rings.

Can this all be done in FLUENT?
I really don't want to write CFD code unless I really have to because I have no knowledge in that area, and it would take me ages to learn.

Thanks

fadiga December 2, 2011 14:32

Those vortex rings in FLUENT
 
Did you end up using FLUENT to model the vortex rings? Am also interested in this since currently I'm still using Matlab and some analytical solutions and would like to take a look at some CFD simulations...

nha1g08 December 2, 2011 14:42

Quote:

Originally Posted by fadiga (Post 334474)
Did you end up using FLUENT to model the vortex rings? Am also interested in this since currently I'm still using Matlab and some analytical solutions and would like to take a look at some CFD simulations...

Yes I did, but how are you simulating them in Matlab?

fadiga December 2, 2011 14:48

Well as I said I was just using the analytical solutions for the vortex rings (they are derived in terms of elliptic integrals). These solutions are only valid for uniform, axisymmetric thin vortex rings so its quite limited, but i've found them useful for some initial work. I am actually more interested in modelling a series of rings, even just two rings to start off. Most work, numerical and experimental, has focused on coaxial colliding rings or dancing rings, or rings in shear flow. I want to look into off-axis rings with some detail. So in Matlab you just need to program the geometry and implement the exact equations...
Could you give some hints how you went about modelling them in Fluent? I really need to validate the results from my current simulation and since I don't have access to experimental facilities...I need to look into some fairly quick numerical simulations...

nha1g08 December 2, 2011 15:02

Quote:

Originally Posted by fadiga (Post 334477)
Well as I said I was just using the analytical solutions for the vortex rings (they are derived in terms of elliptic integrals). These solutions are only valid for uniform, axisymmetric thin vortex rings so its quite limited, but i've found them useful for some initial work. I am actually more interested in modelling a series of rings, even just two rings to start off. Most work, numerical and experimental, has focused on coaxial colliding rings or dancing rings, or rings in shear flow. I want to look into off-axis rings with some detail. So in Matlab you just need to program the geometry and implement the exact equations...
Could you give some hints how you went about modelling them in Fluent? I really need to validate the results from my current simulation and since I don't have access to experimental facilities...I need to look into some fairly quick numerical simulations...

I didnt simulate interactions between two vortex rings, I just simulated a single vortex ring. The main way to do it is to create a nozzle, and make sure the flows go out of that to create a vortex ring. I recommend to read the following journals.

The first one is simulation of vortex ring done in Fluent. Just focus on how they create the vortex ring and ignore the rest of the information for the time being. Pay particular attention to the length of their geometry and boundary conditions, also look at the velocity profile they use for the inlet and try to implement that in Fluent.

The second one is an experimental based one, but if you can implement their geometry, boundary condition and velocity profile in FLUENT, you should be able to create vortex rings.

1.
M. Rosenfeld, et al., "Circulation Generation and Vortex Ring Formation by Conic Nozzles," Journal of Fluids Engineering-Transactions of the Asme, vol. 131, pp. -, Sep 2009.

2
M. Gharib, et al., "A universal time scale for vortex ring formation," Journal of Fluid Mechanics, vol. 360, pp. 121-140, Apr 10 1998.

fadiga December 2, 2011 15:06

Thanks a real lot...this will be a great help.
Don't wanna push it here: I don't have that much experience with FLUENT...how long would you say it took you to implement the model etc..?

Thanks again

nha1g08 December 2, 2011 15:12

Quote:

Originally Posted by fadiga (Post 334479)
Thanks a real lot...this will be a great help.
Don't wanna push it here: I don't have that much experience with FLUENT...how long would you say it took you to implement the model etc..?

Thanks again

It was a third year project, it took me 7 months but I was wasnt constantly working on it for 7 months, maybe timewise maximum 3-4 months. But dont let this put you off! I was completely new to CFD.

Also is this a university project of yours?

rakib21 May 18, 2013 04:34

Did anyone of you do vortex ring simulation in fluent. I need help to simulate vortex ring like this paper:

M. Rosenfeld, et al., "Circulation Generation and Vortex Ring Formation by Conic Nozzles," Journal of Fluids Engineering-Transactions of the Asme, vol. 131, pp. -, Sep 2009.


All times are GMT -4. The time now is 12:39.