Investigation on effects of shock wave on vortical wake flow in a turbine nozzle cascade

Vortical wake flow and its interaction with shock waves in a transonic turbine nozzle cascade were investigated by experimental and numerical methods. Measurements including aerodynamic performance and Schlieren photography were conducted on a validating turbine nozzle cascade. Numerical simulations were performed on both the validating turbine cascade and a single-passage turbine nozzle using two numerical schemes, the RANS and the detached eddy simulation (DES) simulations. The comparison of the wake flow patterns indicated that the DES calculation was more adaptable in simulating the vortical wake flow than the RANS method. Based on the DES results, it was found that, after crossing the shock wave, the vortical wake flow had three changes in its flow characteristic: 1) the vorticity increase in the vortex core; 2) the reduction of the distance between two adjacent vortices with the same direction; 3) the deflection of the entire vortex structure including the vortex core and its preparation stage. Those changes were explained by aerodynamic principles. To further validate the findings, the investigation was carried out at a subsonic condition, and the disappearance of those changes was extra evidence to support that the interaction of the shock wave contributes to the vortex changes.