[Julian121]

Does transient rotor-stator interface need equal pitch on both sides?
The reason why I am asking this is the CFX tutorial on axial turbine stage. In this tutorial, a transient interface was used between unequal pitches.
I am simulating a row of IGV, Rotor, Stator and a casing treatment.
The number of blades are 34, 38, 37 and 120 respectively.
I need to obtain performance maps and analyse the effect of the casing treatment on endwall flow.
I have mainly used steady state simulations but now I need to use transient simulations near to stall.
Should I use transient rotor-stator interface or transient blade row?

[Opaque]

Unfortunately, there is no single answer for this type of problems.

If you really need to study the transient interaction, keep in mind that in ANSYS CFX a transient analysis with transient rotor-stator interfaces is equivalent to a "transient blade row" analysis with Profile Transformation; therefore, I recommend to set up the case as "transient blade row" and select Profile transformation. Then, you can easily upgrade your model with different pitch model changes, Time transformation, Fourier transformation, etc.

Profile transformation allows you to run with a single passage per blade row with an approximation at the row interfaces. You must be careful that the pitch ratio between rows is not too far from 1, so the approximation is reasonable. Because you have 37 blades in the third row, there is no possibility to reduce the model w/o an approximation of some kind.

Keep in mind such simulations are computationally demanding, so you must really know what you want to extract from the results and set it up properly ahead of time. You do not want to wait days, and realize the information you need is not being computed/stored or else when finished.