Crossflow Banki water turbine simulation

[Anonymous]

Hi everyone,

I am an engineering student, and I am using the student versions of Autodesk Inventor and CFD software.
I am working on the design of a Banki water turbine to complete the credits for a renewable energy course.

I would like to simulate the behavior of the turbine in Autodesk CFD software.
I was able to set the model, assign materials and set the boundary conditions for the inlet and outlet, and the MRF zone following the Autodesk (Turbomachinery tutorial and Turbomachinery best practices) tutorials.
The problem I have is that since the fluid is just water, the simulation does not correctly represent the turbine's operation. The turbine works completely flooded with water, a condition that should not happen in reality.

I would like to know if it is possible to perform the simulation of two fluids mix (water and air) and what steps I must take to be able to set the model properly. I read the article of two phase fluids and but I do not know if it fits my model, nor how to set it in the simulation correctly.

Enclosed a screenshot simulation environment with the crossflow water turbine model.

I hope you can help me.

Regards,

Leonardo.

[apolo_vanderberg]

While it will be more resource and mesh intense than what you have now, you might want to look at Free Surface modeling. 

This would allow you to represent a non-flood condition and how the water would impact the turbine.

There is a webinar that has been posted to youtube on this walking through the typical best practices that you could adapt to your model.

[Anonymous]

Hi Apolo,

Thanks for your reply.
I will try to your suggestion. Although I am afraid that the resource requirements could be a problem (the rotor is in a moving reference frame). I have not a dedicated mainframe to simulate the turbine, I am using my personal computer (I7 6500U, 8GB DDR4 RAM, 2GB DDR5 NVIDIA, 500GB SSD).

Can I get results of output torque or output power of the turbine with the free surface analysis?

Thanks,

Leonardo.

[Jon.Wilde]

Looks like you could run this in 2D, which would be much simpler, at least to test to see if you are getting good results with the free surface capabilities that we have in CFD.

8GB RAM isn't too much, to be honest 🙂

[apolo_vanderberg]

Leonardo, 

For Free Surface, this can be mesh sensitive to properly capture streams. Depending on how this turbine behaves it can be on the edge of some of our assumptions behind the Free Surface solver. For this reason as Jon mentioned, if you can run this as a test in 2D, you can possibly get good insight and keep this within your 8GB resources.

As 3D this may require more ram than you have available. 

I'd recommend reading some of the Help documentation on Free Surface as well as the posted webinar and then see about testing in 2D before moving to 3D

[Anonymous]

Hello Jon and Apollo,

Thanks to your help I was able to configure the simulation to model the operation of the water turbine.
Attached a video where you can see the cross flow of the water turbine. I also attached the Autodesk CFD project file, in case anyone wants to run the simulation.

The simulation conditions were as follows:

Free spin rotating region
Inlet: 2.5 L / s
Outlet: Pressure (0 Pa Gage)
Load: 0.35Kgm2

I could also get the results from rotating regions from the tab results.

I have to refine the mesh and run greater number of iterations to reach the permanent regime of rotation speed.

I am open to any other suggestions to improve the simulation.

Thank you very much for answering my questions and for the support provided.

Best regards,

Leonardo.