Learning Forum

[Luis]

Hello everyone
my aim is to simulate the fluid structure interaction in order to obtain the stress exerted on the strut that bears the rotating propeller of a ship. For this reason I need to obtain the propeller (540rpm) pressure pulse on the strut and then coupling it with structural mechanic module. Should I consider the propeller geometry or an actuator disk with a momentum source? Any ideas on how to set the workflow?

thank you

[Karthik R]

Hello Luis,

You can use FSI between Fluent and Mechanical to do this. You can couple them together. You will get the flow field from the FLuid simulation and use this to estimate the stresses on Mechanical. Here are some video tutorials on how you can set-up the workflow in ANSYS. This is a two part video.

I hope this helps.

Best Regards,

Karthik

[Luis]

Thank you, very useful. I coupled transient structural and fluent module. What about the propeller? Should I model it or use a kind of actuator disk? And which is the cell zone condition?
thank you for your help
Luis

[Karthik R]

Hello Luis,

It really depends on your final goal, the degree of accuracy, and availability of computational resources. Fluent has the capabilities of modeling this both ways. You will have to make a judgement call based on the factors I mentioned above. If you google 'Actuator disk Fluent', it displays a huge list of modeling approaches you could learn from to complete your model. It is however very important to know the assumptions you are making in your modeling approach. Here is a very nice lecture notes from MIT which delineates all the assumptions based on an actuator disk model. You might want to take a look at it to understand and decide which modeling approach you want to take.

https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node86.html

I hope this helps.

Best Regards,

Karthik

[Luis]

Thank you! Last question: is there a way to consider this kind of fluid domain for the cfd part (maybe a kind of "virtual" control volume)? The bottom is supposed to be the sea floor, while the top is the bottom hull of my ship (the tunnel, where the strut is inserted). The problem is that, doing the boolean subtract, the two geometries intersect each other (the top of the struct actually is fixed inside the hull where there is no fluid) and I have manifold problem.

Below a picture of my domain

Thank you

Luis

 

[Karthik R]

Hello Luis,

Based on your question, it seems like you are having some issues with performing a Boolean operation in DM (I'm assuming). Could you please identify the parts on which you have this issue? Could you please post the exact error message.

To provide you with a generic answer your question, yes. You should be able to subtract the solid region from your fluid region in either DM or SC. For a more specific answer, could you please label the parts in your geometry?

Also, I'd recommend opening a new thread if you are switching gears from modeling advise to geometry issue. Please create a new thread under 'Geometry' in 'Pre-Processing'.

Here are some Guidelines which might help you find faster solutions to your problem on this community.

Thank you.

Best Regards,

Karthik