# Three-stage turbine with cavities

An unsteady solution of a three-stage high-pressure steam turbine

**3 NVIDIA C1060 GPUs****1 hour for 15 rotor passings****3.5 million grid nodes**

Turbostream uses Jameson’s dual time stepping algorithm for time-accurate calculations – in this case 150 outer time steps were used per rotor passing, each needing approximately 30 inner time steps to converge. For this experimental rig, the the blade numbers are such that only a single passage is needed for every row.

The figure shows contours of the absolute Mach number and the entropy function at mid-span. The main feature is the wakes from the blades convecting through the machine. Although not shown, the mesh also includes hub and shroud cavities. The combination of a time-accurate simulation method and fully resolved cavities increases the fidelity of the calculation, but comes at the cost of a one or two orders increase in the total run time. However, with Turbostream a designer can still perform many such calculations in a single day.

The simulation is based on a steady-state calculation by Rosic et al. (The Importance of Shroud Leakage Modeling in Multistage Turbine Calculation).