| An unsteady viscous flow solver based on the Runge-Kutta scheme has been developed. Pseudo-time step technique has been incorporated to provide efficient simulation of unsteady flows. Utilization of the pseudo-time approach reduces the computational time by a factor varying from 5 to 25 times in comparison with the original solver. The results of the stability analysis of the dual time step scheme are used to establish an optimum pseudo-time step based on the local CFL, VonNeuman numbers and the ratio of pseudo-to-physical time steps.; The code has been validated against the analytical and experimental data. The influence of the numerical aspects (artificial dissipation, grid density etc.) on the accuracy of the prediction of the wake decay, transition, flow over a cylinder has been analyzed. Based on the results of the test cases, modifications to the k-ϵ model to improve the accuracy in the regions with dominant normal stresses are incorporated.; Developed solver has been used for the numerical simulation of the complex steady and unsteady turbomachinery flows, including unsteady transitional flows in compressor and turbine, leading edge film cooling and secondary flow simulations. Three low Re k-ϵ turbulence models have been assessed for their ability to predict the unsteady transitional flows. Good agreement with the measured data has been achieved. The numerical solver was able to predict major features, associated with the wake-induced transition on blade (wake induced transitional strip, wake induced turbulent strip, etc.). Analysis and interpretation of the results from the flow simulation have been carried out to understand additional flow physics associated with the transitional, film cooling and secondary flows. |
