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-   -   Cyclic Symmetry - transient- axial turbine case. (https://www.cfd-online.com/Forums/main/116113-cyclic-symmetry-transient-axial-turbine-case.html)

 Gowrav April 13, 2013 05:17

Cyclic Symmetry - transient- axial turbine case.

Hi Everyone..
As a part of masters project, am doing flow analysis of axial micro turbine to evaluate pressure on blades.. my previous simulations resulted into singularity error while transferring result to FSI analysis.. i ve refined the mesh to fix this, which increased the mesh size now nearly 7 million elements. Which will occupy my computational resources and will eat lots of time than previous.
So i ve bn suggested to run the same with cyclic symmetry..
i am using 3d sliding mesh in fluent.. whether symmetry will work with that. ?
I am having 8 blades -symmetric- i have taken 1 full and 2 halves of adjacent blades for symmetric analysis. Is this correct way fr symmetry..
i am getting very low mass flow rate with same pressure in -pressure out bcs,, also i have not corrected pressures for symmetric analysis..
Kindly correct me where its going wrong. and share opinions to fix this.
Gowrav

 Far April 13, 2013 08:15

You are talking about periodic boundary condition to reduce blade count hence less no of nodes.

The number of blades for periodic case depends upon ratio of number of blades upstream and downstream. The main goal to have equal pitch on both sides. For example if you have 6 blades upstream and 12 downstream then you will select one blade from upstream blade row and two blades from downstream blade row.

It is possible that you don't get integral number for the ratio of blades from upstream and downstream row. In this case you have to approximate analysis. For example if you have 22 blades upstream and 41 downstream. In this case ratio is 1.86 and it is not possible to have exact no of blades upstream and downstream. Now you need to approximate. Assume you have 22 blades upstream (real) and 44 blades downstream (approximation)

Quote:
 i am getting very low mass flow rate with same pressure in -pressure out bcs,, also i have not corrected pressures for symmetric analysis.. Kindly correct me where its going wrong. and share opinions to fix this.