is Transient solution really needed for Propellers?
 

I am solving thrust and torque on contra-rotating propellers ( there are two propellers rotating in counter sides)

Do I actually need a transient solution or Sliding mesh+steady state solver is enough?

thanks.

Isn' t the moving mesh approach intrinsically transient? If you want/have to use a steady solution you might try the moving reference frame approach, but with propellers with few blades and/or high interferences between each other (thinking about your counter rotating case) you will loose some accuracy and won't capure certain phenomenas wich might at the end give out meaningless results.

My two 0,02€

you should go for the multiple reference frame approach first (steady state) and if not satisfied then go for the sliding mesh (transient). Keep in mind for sliding mesh to give you accurate results you may need big machines !!!!!!!

yes huge machines actually :)
how about the size of time step, do u have an idea about its proper scale?

you should be able to calculate it from the pitch and rpm. checkout tut on turbo-machinery in CFX

Hi Emre

Have you tried the transient sliding mesh on this contra-rotating propeller? May I ask how you dealt with the interface between the contra-rotating zones?

For my case, if I set a pair of contra-rotating zones using mesh motion, the calculation would break immidateley and said "Node 1: Process 9092: Received signal SIGSEGV".

Do you know the reason and how to solve this?

Thank you very much.
Nathan

Yes i overcomed this issue ten years before ;)

Please check your interface surface mesh. İt should be unconformally mismatched or a very scewed mesh cell is encountered. And please start with MRF solution, if you still get same error check again interface surfaces if they have different diameters or have a big gap between them.. this would be a mesh issue !

Thanks Emre, and I will try it as you suggested.

I didn't notice that it has been more than ten years;). It's really kind of you for replying me.:D

Thank you again and wish you all the best.
Nathan