Cycle/Secondary Flow Analysis
Gas Turbine cycle analysis is available for small engines such as
microturbines, missle jet engines, etc.  For these cycles, either Gasturb
(developed by Joachim Kurtze) or NASA's NEPP code is used.  
Unconventional cycles, such as semi-closed-loop gas turbines have been
successfully modeled using custom codes programmed in FORTRAN.  

Secondary flow analysis is performed using Calculix.  Calculix is an open
source finite element analysis (FEA) code and contains the capability to
model secondary flow systems.  Flow systems are modeled using a network
analysis of one dimensional flow elements.  The fluid flow model can be
coupled to the solid FEA model, so full fluid-structural thermal analyses can
be completed.