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is Transient solution really needed for Propellers?

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Old   December 20, 2011, 15:54
Default is Transient solution really needed for Propellers?
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Emre G
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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.
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Old   December 22, 2011, 17:56
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Quote:
Originally Posted by emreg View Post
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.

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Old   December 24, 2011, 02:25
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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 !!!!!!!
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Old   December 25, 2011, 17:20
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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?
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Old   December 25, 2011, 23:43
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you should be able to calculate it from the pitch and rpm. checkout tut on turbo-machinery in CFX
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