Effect of constant and variable radii fillet on secondary flow field of transonic turbine stage's Nozzle Guide Vane

In this present work, efforts are made to understand the effect of constant and variable radii fillet on secondary flow losses in Nozzle Guide Vane of the transonic turbine stage. Constant and variable radii fillets near vane-endwall juncture are designed using shape parameters like leading edge radius and minimum angle. Results are discussed using topological features of the flow field, Mach and density contours. Separation lines associated with inlet boundary layer and passage vortex, saddle point and attachment nodes are resolved. Variable radii fillet outperforms the constant radii fillet by reducing the height of three dimensional flow regime affected by secondary flow. It removes the separation bubble near the trailing edge. Increment in leading edge radius increases the movement of these flows towards midspan while the effect of minimum angle is found to be insignificant.