A Numerical Investigation of Time Resolved Flows Around Turbine Blades.

The complex nature of turbomachinery flows and the scale of associated flow phenomena such as shock waves and vortex shedding, apply constraints to the methods by which the flow can be analysed experimentally. Computational techniques have quite successfully been applied to the flow around turbine blades, but the transient and periodic phenomena observed in experimental studies have not been fully investigated. In this work an original working computational code is presented for time-resolved flows around turbine cascades. The code has been verified using test cases relevant to transonic flow. Some of the problems associated with computational techniques have been highlighted; these include the large number of schemes that are available, each with its own advantages and disadvantages. The code has been applied to a geometry representing highly loaded turbine blading currently under study at the National Research Council of Canada; this was also used extensively in previous computational and experimental investigations. The blading chosen has a relatively thick trailing edge, necessitated by cooling considerations. A distribution of the flow properties on the surface of the blade has been determined, from which an equivalent water table model has been designed based on the principle of the hydraulic analogy. The water table model thus generated represents a further method for experimentally investigating flow phenomena without the complexity of analysing very high frequency oscillations in situ. The timeresolved flow field has been computed showing unsteady phenomena. The unsteady phenomena have been shown to compare favourably with the unsteady features observed in preliminary experimental results. In the process, energy separation has been predicted to occur not only in the coupled wake region, but also for the first time within Kelvin-Helmholtz instabilities present in the trailing edge shear layers.