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-   -   is Transient solution really needed for Propellers? (http://www.cfd-online.com/Forums/fluent/95507-transient-solution-really-needed-propellers.html)

emreg December 20, 2011 14:54

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.

sail December 22, 2011 16:56

Quote:

Originally Posted by emreg (Post 336510)
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

Far December 24, 2011 01:25

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 !!!!!!!

emreg December 25, 2011 16:20

Quote:

Originally Posted by Far (Post 336903)
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?

Far December 25, 2011 22:43

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


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